Using a dog demography field study to inform the development of an agentbased computer simulation. Evaluating owned dog population control
interventions in a small, semi-urban community in Mexico
by
Luz Maria Kisiel
A Thesis
presented to
The University of Guelph
In partial fulfillment of requirements
for the degree of
Master of Science
in
Population Medicine
Guelph, Ontario, Canada
© Luz Maria Kisiel, January, 2017
ABSTRACT
USING A DOG DEMOGRAPHY FIELD STUDY TO INFORM THE DEVELOPMENT
OF AN AGENT-BASED COMPUTER SIMULATION. EVALUATING OWNED DOG
POPULATION CONTROL INTERVENTIONS IN A SMALL, SEMI-URBAN
COMMUNITY IN MEXICO
Luz Maria Kisiel
University of Guelph, 2016
Co-Advisors:
Dr. Amy Greer
Dr. Andria Jones-Bitton
This thesis evaluates the potential effects of different dog population control
interventions in a small, semi-urban community in Mexico. First, a cross-sectional study was
conducted to characterize dog ecology and demography in Villa de Tezontepec, Hidalgo.
Approximately 65% of the households owned one or more dogs. The majority of owned dogs
(76%) were not sterilized, and less than half (45%) were kept confined. Second, a stochastic,
agent-based simulation model was constructed to determine the projected impact of surgical
sterilization interventions and increased dog confinement on the owned dog population size for
this community. The model outputs suggested that surgical sterilization interventions focused
only on young dogs (prior to sexual maturity) could yield greater reductions in population size
than surgical interventions focused on dogs of mixed age. The information generated in this
thesis can help to identify considerations for the design and implementation of dog population
control programs in developing countries.
iii
DEDICATION
This thesis is dedicated to the memory of my late dog Tommy, as well to all dogs that have been
a part of my life.
Dogs are amazing creatures whose lives are worth saving and protecting.
iv
ACKNOWLEDGEMENTS
To my husband, Mariusz Kisiel, for always encouraging me to take risks and follow my
dreams, and for his continued support and unconditional love throughout this journey.
To my advisors Dr. Amy Greer, and Dr. Andria Jones-Bitton, thank you for taking a
chance with me and for all of your patience, advice, and guidance. You have both provided me
with continuous support and knowledge throughout this research project. To Dr. Jan Sargeant,
Dr. Jason Coe, and Dr. Tyler Flockhart for their advice, encouragement and contributions. Thank
you all for helping me improve my work and writing. It has been a privilege and honour to work
with all of you.
Thank you to Dr. Erick Canales Vargas, and Dr. Alejandro Reynoso Palomar for their
support, guidance, and help during my fieldwork in Mexico.
I would like to thank the Health Services of the State of Hidalgo and the municipal
government of Villa de Tezontepec for their support of this research study; the Faculty of
Veterinary Medicine of the Autonomous University of Hidalgo and the National College of
Professional Technical Education (CONALEP) in Villa de Tezontepec for the participation of
their students in the administration of questionnaires; the local volunteers for their cooperation
and hospitality, especially, Mrs. Lorena Orozco for her logistical support, and to all participants
in the survey.
I would like to thank Wayne Johnston, from the University of Guelph library, for his help
in the development of the online database. I would also like to acknowledge Dr. Elly Hiby and
Dr. John Boone, for their guidance regarding stray dog population estimation methodologies.
I would like to thank Tatiana Gozima, from the Anylogic Company, for helping me with
alternative solutions to some of the conflicts I had when I was developing my agent-based
v
model.
I would like to gratefully acknowledge a Mathematics of Information Technology and
Complex Systems (MITACS) Globalinks Award (IT05893) and the Canada Research Chairs
Program for their funding.
I am so very grateful for having such supportive lab friends, especially to Kelsey Spence
for making this journey more enjoyable and for helping me believe in myself when I had selfdoubt.
To my parents, Arturo Tapia Taylor and Lucrecia Quiroz Contreras for their support and
encouragement, especially I want to thank my mom for her hard work and contributions during
my field work while in Mexico, for accompanying me to train students, taking pictures of my
activities, and helping me with the data entry of all the survey questionnaires. To my brother
Arturo Tapia Quiroz, for all his advice and guidance in research methodologies.
vi
STATEMENT OF WORK DONE
Luz Maria Kisiel with the advisement of, and collaboration with, Dr. Andria Jones-Bitton
and Dr. Amy Greer, and on-going discussion with members of her advisory committee, Dr. Jan
Sargeant, Dr. Jason Coe, and Dr. Tyler Flockhart, and the support of external collaborators, Dr.
Erick J. Canales Vargas, and Dr. Alejandro Reynoso Palomar, conducted a cross-sectional study
to collect information on the demography and ecology of owned dogs in Villa de Tezontepec,
Hidalgo, Mexico. Luz Maria Kisiel, with support from Dr. Amy Greer, also developed an agentbased model based on the empirical data collected in Villa de Tezontepec, Hidalgo to evaluate
the impact of different scenarios regarding surgical sterilization and dog confinement control.
Both research studies are a part of this thesis.
CHAPTER 1: Literature review.
Luz Maria Kisiel searched multiple databases for articles in English and Spanish, as well
as books from the university library relevant to the topics under study. The literature review was
written by Luz Maria Kisiel, under the guidance of, and with editing from, Dr. Andria JonesBitton and Dr. Amy Greer. Additional input and revisions were received from Dr. Jan Sargeant,
Dr Jason Coe, and Dr. Tyler Flockhart.
CHAPTER 2: Cross-sectional study
Through collaboration with, and advisement of Dr. Andria Jones-Bitton, and Dr. Amy
Greer, Luz Maria conducted a cross-sectional study in Villa de Tezontepec Mexico. Dr. Andria
Jones-Bitton provided the questionnaire from which Luz Maria Kisiel made modifications for the
cross-sectional study (both in English and Spanish). Mr. Wayne Johnston helped Luz Maria
Kisiel develop the online database to enter the data collected during the study. Luz Maria Kisiel,
with the collaboration of Dr. Erick Canales Vargas, recruited the study location. Under the
vii
advisement of Dr. Erick Canales Vargas, Luz Maria obtained the collaboration of the
undergraduate students of the Autonomous University of Hidalgo, to administer the
questionnaire. Luz Maria trained all questionnaire administrators. Questionnaires were
administered by Luz Maria Kisiel and local students and volunteers. Data were translated,
entered, cleaned and analyzed by Luz Maria Kisiel. Descriptive statistical analysis was
completed by Luz Maria Kisiel, with the advisement of Dr. Andria Jones-Bitton and Dr. Amy
Greer. Drafts of the manuscript were written by Luz Maria Kisiel, and reviewed and edited by
Andria Jones-Bitton and Dr. Amy Greer. Additional input and revisions were received from Dr.
Jan Sargeant, Dr. Jason Coe, Dr. Tyler Flockhart, Dr. Erick J. Canales Vargas, and Dr. Alejandro
Reynoso Palomar.
CHAPTER 3: Agent-based model development
Luz Maria Kisiel developed the agent-based dog population model with support from Dr.
Amy Greer. The model outcomes of interest were analyzed by Luz Maria Kisiel under the
advisement of Dr. Andria Jones-Bitton and Dr. Amy Greer. Sensitivity analysis for the model
parameters where empirical information was limited, was performed by Luz Maria Kisiel under
the guidance of Dr. Amy Greer. The manuscript was written by Luz Maria Kisiel, and reviewed
and edited by Dr. Andria Jones-Bitton and Dr. Amy Greer. Additional input and revisions were
received from Dr. Jan Sargeant, Dr. Jason Coe and Dr. Tyler Flockhart.
CHAPTER 4: Conclusions
This chapter was written by Luz Maria Kisiel, and reviewed and edited by Dr. Andria
Jones-Bitton and Dr. Amy Greer. Additional input and revisions were received from Dr. Jan
Sargeant, Dr. Jason Coe and Dr. Tyler Flockhart.
viii
TABLE OF CONTENTS
CHAPTER ONE ......................................................................................................................... 1
Introduction, Literature Review, Rationale and Objectives ................................................... 1
1. Introduction and literature review .................................................................................... 1
1.1. Introduction .................................................................................................................... 1
1.2. Dog classifications ......................................................................................................... 1
1.3. Free-roaming dogs ......................................................................................................... 2
1.3.1. Owned free-roaming dog characteristics ................................................................ 3
1.3.2. Stray dog characteristics ......................................................................................... 5
1.3.3. Feral dog characteristics ......................................................................................... 6
1.4. Dog overpopulation ....................................................................................................... 7
1.5. The impacts of dog overpopulation ............................................................................... 8
1.5.1. Animal welfare concerns ........................................................................................ 8
1.5.2. Impact on wildlife ................................................................................................... 9
1.5.3. Impact of dogs on livestock .................................................................................. 10
1.5.4. Impact on environment ......................................................................................... 10
1.5.5. Impact on public health ......................................................................................... 11
1.6. Methods for estimating dog abundance ....................................................................... 13
1.6.1. Owned dog abundance estimation methods .......................................................... 13
1.6.2. Free-roaming dog abundance estimation methods ............................................... 14
1.6.2.1. Street surveys ................................................................................................. 15
1.7. Methods to address the free-roaming dog population.................................................. 16
ix
1.7.1. Education .............................................................................................................. 16
1.7.2. Legislation............................................................................................................. 17
1.7.3. Environmental controls ......................................................................................... 20
1.7.4. Handling and removal of free-roaming dogs ........................................................ 21
1.7.5. Capture and return, re-homing, or release ............................................................ 22
1.7.6. Reproductive control ............................................................................................. 23
1.7.6.1. Surgical sterilization ...................................................................................... 23
1.7.6.2. Non-surgical contraception ............................................................................ 24
1.8. Mathematical modeling and simulation ...................................................................... 27
1.8.1. Population dynamic models .................................................................................. 28
1.8.2. Agent-based models .............................................................................................. 29
1.8.3. Applications of population dynamic models ........................................................ 32
2. Thesis rationale and objectives ........................................................................................ 33
3. Format of the thesis .......................................................................................................... 34
4. References .......................................................................................................................... 35
CHAPTER TWO ...................................................................................................................... 60
Owned dog ecology and demography in Villa de Tezontepec, Hidalgo, Mexico................. 60
Abstract.................................................................................................................................. 60
1. Introduction ....................................................................................................................... 61
2. Materials and methods ..................................................................................................... 64
2.1. Questionnaire survey design ........................................................................................ 64
2.2. Study region and neighbourhood selection .................................................................. 65
x
2.3. Household selection ..................................................................................................... 65
2.4. Door-to-door household survey ................................................................................... 67
2.5. Owned dog density ...................................................................................................... 68
2.6. Data analysis ................................................................................................................ 68
3. Results ................................................................................................................................ 69
3.1. Survey participation and household characteristics ..................................................... 69
3.2. Dog ownership ............................................................................................................. 69
3.3. Owned dog demographics............................................................................................ 70
3.3.1. Age, Sex and Spay/Neuter Status ......................................................................... 70
3.3.2. Owned dog mortality ............................................................................................ 70
3.3.3. Reproductive indices and litter survivorship ........................................................ 71
3.4. Owned Dog Ownership Patterns.................................................................................. 72
3.5. Dog management and handling practices .................................................................... 72
4. Discussion .......................................................................................................................... 73
5. Limitations ......................................................................................................................... 81
6. Conclusions ........................................................................................................................ 82
7. Conflict of interest statement ........................................................................................... 82
8. Acknowledgements ........................................................................................................... 82
9. References .......................................................................................................................... 83
CHAPTER THREE ................................................................................................................ 101
xi
Modeling the effect of surgical sterilization and confinement on owned dog population size
in Villa de Tezontepec, Hidalgo, Mexico, using an agent-based computer simulation model
................................................................................................................................................... 101
Abstract................................................................................................................................ 101
1. Introduction ..................................................................................................................... 102
2. Materials and methods ................................................................................................... 105
2.1 Model description ....................................................................................................... 105
2.2. Model Synthetic Population Structure ....................................................................... 105
2.3. Model Parameterization ............................................................................................. 106
2.4. Model parameter assumptions ................................................................................... 107
2.5. Immigration and Emigration ...................................................................................... 107
2.6 Model life cycle states ................................................................................................ 108
2.6.1. Male Dogs ........................................................................................................... 108
2.6.2. Female Dogs ....................................................................................................... 108
2.7. Model output .............................................................................................................. 109
2.8. Base case scenario...................................................................................................... 110
2.9. Population Control Interventions ............................................................................... 110
2.9.1. Surgical Sterilization Interventions..................................................................... 110
2.9.2. Dog Confinement Intervention ........................................................................... 111
2.9.3. Combined Surgical Sterilization (mixed age group) and Dog Confinement
Intervention ................................................................................................................... 112
2.10. Sensitivity analyses .................................................................................................. 112
3. Results .............................................................................................................................. 113
xii
3.1. Base case simulations ................................................................................................ 113
3.2. Mixed Age Surgical Sterilization Intervention .......................................................... 114
3.3. Young Age Surgical Sterilization Intervention.......................................................... 114
3.4. Dog Confinement Intervention .................................................................................. 115
3.5. Combined Mixed Age Surgical Sterilization (21 surgeries/month) And Dog
Confinement...................................................................................................................... 115
3.6. Sensitivity analyses .................................................................................................... 116
4. Discussion ........................................................................................................................ 117
5. Limitations ....................................................................................................................... 121
6. Conclusion ....................................................................................................................... 122
6. Conflict of interest statement ......................................................................................... 123
7. Acknowledgements ......................................................................................................... 123
8. References ........................................................................................................................ 123
CHAPTER FOUR................................................................................................................... 142
Conclusions, study limitations and recommendations for future research ....................... 142
4. Thesis summary and key recommendations ................................................................ 142
4.1. Summary .................................................................................................................... 142
4.2. Study limitations ........................................................................................................ 147
4.3. Key recommendations for the local community ........................................................ 148
4.4. Recommendations and future directions for research ................................................ 149
4.5 References ................................................................................................................... 151
APPENDIX A .......................................................................................................................... 154
xiii
Owned dog ecology and demography in Villa de Tezontepec, Hidalgo, Mexico............... 154
A.1. Villa de Tezontepec – HOUSEHOLD Questionnaire Identifiers ................................. 155
A.2. Villa de Tezontepec – HOUSEHOLD Questionnaire................................................... 156
A.3. Villa de Tezontepec – Cuestionario HOGAR Identificadores ...................................... 167
A.4. Villa de Tezontepec - Cuestionario HOGAR ............................................................... 168
APPENDIX B .......................................................................................................................... 179
Modeling the effect of surgical sterilization and confinement on owned dog population size
using an agent-based computer simulation .......................................................................... 179
B.1. Comparison of the impact of increasing the annual mortality rate for puppies from 5%
(A) to 10% (B) to 30% (C) for the mixed age sterilization interventions............................. 180
B.2. Comparison of the impact of increasing the annual mortality rate for young dogs from
10% (A) to 20% (B) to 30% (C) for the mixed age sterilization interventions. ................... 181
B.3. Comparison of the impact of increasing the annual mortality rate for adult dogs from
1.5% (A) to 3% (B) to 7.5% (C) for the mixed age sterilization interventions. ................... 182
B.4. Comparison of the impact of increasing the annual pregnancy rate from 10% (A) to 26%
(B) to 40% (C) for the mixed age sterilization interventions................................................ 183
B.5. Comparison of the impact of increasing the annual mortality rate for puppies from 5%
(A) to 10% (B) to 30% (C) for the young age sterilization interventions............................. 184
B.6. Comparison of the impact of increasing the annual mortality rate for young dogs from
10% (A) to 20% (B) to 30% (C) for the young age sterilization interventions. ................... 185
B.7. Comparison of the impact of increasing the annual mortality rate for adult dogs from
1.5% (A) to 3% (B) to 7.5% (C) for the young age sterilization interventions. ................... 186
xiv
B.8. Comparison of the impact of increasing the annual pregnancy rate from 10% (A) to 26%
(B) to 40% (C) for the young age sterilization interventions................................................ 187
xv
LIST OF TABLES
CHAPTER ONE
Table 1. Advantages, disadvantages, and biases associated with methods used to estimate the
abundance of free-roaming dogs. .................................................................................................. 58
Table 2. Mathematical models used to describe domestic dog population dynamics and to
evaluate different strategies for dog population control. Information in the table includes dog
population of interest, study location, model methodology used, and model objective. .............. 59
CHAPTER TWO
Table 1. Number of people categorized by age, median number of people per household, median
age of people per household, and male to female ratio in 328 households in 4 neighborhoods
surveyed in Villa de Tezontepec, Hidalgo, Mexico, 2015a. ......................................................... 94
Table 2. Mean, median and range of number of dogs per dog owning household, the human to
owned dog ratio, the estimated total number of owned dogs and the estimated absolute owned
dog density for four neighborhoods surveyed in Villa de Tezontepec, Hidalgo, Mexico, 2015. . 95
Table 3. Age, sex, and spay/neuter structure of the owned dog population, in Villa de
Tezontepec, Hidalgo, Mexico, 2015. (n=428 dogs) ..................................................................... 96
Table 4. Reasons reported by dog owners for not spaying or neutering their owned dogs, in Villa
de Tezontepec, Hidalgo, Mexico, 2015. ....................................................................................... 97
Table 5. Sources of owned dogs in Villa de Tezontepec, Hidalgo, Mexico, 2015. (n=411 dogs)g
....................................................................................................................................................... 98
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CHAPTER THREE
Table 1. Model parameters describing the transition rates and/or times for individual dogs to
move between the different model states. Single fixed values were indicated by “N/A” in the
distribution column. .................................................................................................................... 129
Table 2. Initial conditions of the agent-based model evaluating owned dog population control
interventions in Villa de Tezontepec, Hidalgo Mexico. ............................................................. 131
Table 3. Surgical and confinement interventions examined using the agent-based model
evaluating owned dog population control interventions in Villa de Tezontepec, Hidalgo Mexico.
..................................................................................................................................................... 132
Table 4. Model simulation results. For each intervention, the model was run 1000 times with the
outcome of interest being the total population size after 20 years. Outcomes are aggregated
across all model iterations and summarized as mean population size, standard deviation, median
population size and range............................................................................................................ 133
Table 5. Difference in mean population size between the base case scenario and across all
intervention scenarios of the same type, for the mixed age surgical sterilization interventions and
the young age surgical sterilization. Percentages in brackets are the % reduction in mean
population size between the two interventions. .......................................................................... 134
Table 6. Difference in mean population size between mixed age surgical sterilization and young
age surgical sterilization interventions within the same level of surgical capacity. Level 1
represents a surgical capacity of 21 surgeries per month, level 2 represents 42 surgeries per
month, and level 3 represents 84 surgeries per month. Percentages in brackets are the %
reduction in mean population size between the two interventions. ............................................ 135
xvii
Table 7. Differences in mean population size between the base case scenario and across all
intervention scenarios and combinations of the same type, for the dog confinement intervention
and the combined mixed age surgical sterilization (capacity level 1) and dog confinement
intervention. Level 1 represents a surgical capacity of 21 surgeries per month. Percentages in
brackets are the % reduction in mean population size between the two interventions. .............. 136
Table 8. Difference in mean population size between combined intervention at surgical capacity
level 1, mixed age surgical sterilization (without dog confinement), and dog confinement. Level
1 represents a surgical capacity of 21 surgeries per month. Percentages in brackets are the %
reduction in mean population size between the two interventions. ............................................ 137
xviii
LIST OF FIGURES
CHAPTER TWO
Figure 1. Age population pyramid of owned dogs, in Villa de Tezontepec, Hidalgo, Mexico,
2015............................................................................................................................................. 100
CHAPTER THREE
Figure 1. State chart for male dogs describing the individual life states and transitions in the
agent-based model evaluating owned dog population control interventions in Villa de
Tezontepec, Hidalgo Mexico. ..................................................................................................... 138
Figure 2. State chart for female dogs describing the individual life states and transitions in the
agent-based model evaluating owned dog population control interventions in Villa de
Tezontepec, Hidalgo Mexico. ..................................................................................................... 139
Figure 3. Impact of mixed age surgical sterilization and young age surgical sterilization
interventions after 20 years. Each box represents a summary of the model outcome (population
size) across 1000 model replicates. The top and bottom of each box are the 25th and 75th
percentiles, and the line inside the box is the median dog population size. The top whiskers are
the minimum and maximum values of population size, excluding outliers, which are represented
in the figure by solid circles. The dashed line represents the population community capacity.
Panel A: Mixed age sterilization, Panel B: young age sterilization ............................................ 140
Figure 4. Impact of dog confinement alone (Panel A) and the combination intervention (21,
mixed age sterilizations per month + dog confinement: Panel B). Each box represents a summary
of the model outcomes across 1000 model replicates. The top and bottom of each box are the 25th
and 75th percentiles, and the line inside the box is the median dog population size. The top
whiskers are the minimum and maximum values of population size, excluding outliers, which are
xix
represented in the figure by solid circles. The dashed line represents the population community
capacity. ...................................................................................................................................... 141
xx
LIST OF ABBREVIATIONS
ABMs
Agent-based Models
ACC&D
Alliance for Contraception in Cats and Dogs
ALG
Amy L. Greer
CNR
Capture, Neuter, and Release
CONALEP
National College of Professional Technical Education
FSH
Follicle-stimulating hormone
GnRH
Gonadotropin-releasing hormone
ICAM
International Companion Animal Management Coalition
ICF
Inner City Fund
INAP
Instituto Nacional de Administracion Publica
INEGI
National Institute of Geography and Statistics
INFDM
Instituto National para el Federalismo y el Desarrollo Municipal
Km
Kilometer
LH
Luteinizing hormone
MITACS
Mathematics of Information Technology and Complex Systems
ODK
Open Data Kit
OIE
World Organization for Animal Health
OPS
Organización Panamericana de la Salud
PPS
Probability proportional to size
SD
Standard Deviation
SSEH
Health Services in the State of Hidalgo
WHO
World Health Organization
WSPA
World Society for the Protection of Animals
ZP
Zona Pellucida
xxi
CHAPTER ONE
Introduction, Literature Review, Rationale and Objectives
1. Introduction and literature review
1.1. Introduction
The uncontrolled growth of a dog population can have a negative impact on public health and
can create additional socioeconomic, political, and animal welfare problems (Downes et al.,
2009; World Organization for Animal Health (OIE), 2016; Salamanca et al., 2011). Dogs are the
main vector (75% - 99%) of rabies transmission to humans (Garde et al., 2013). It is estimated
that canine mediated rabies kills between 30,000 and 60,000 people annually worldwide (Garde
et al., 2013). Humans are largely responsible for the survival of dogs (Salamanca et al., 2011).
For example, human decisions can act to increase or decrease the abundance of dogs, the
interactions between dogs and people, and the risk of diseases and aggressive behaviour (Beck,
1975; Salamanca et al., 2011). Computer simulation models of dog populations can offer
biologists, veterinarians, and public health professionals a powerful tool to help them evaluate
the effects of dog population management programs and zoonotic disease control measures (Pitt
et al., 2003). This literature review focuses on dog ecology and dog overpopulation in
developing countries, as well as on computer simulation modeling, specifically agent-based
models for the evaluation of dog population control interventions.
1.2. Dog classifications
Dogs have traditionally been classified based on their origins, free-roaming status,
behavioural or ecological traits, as well as their dependency on people (Boitani et al., 2007).
Dogs’ associations with humans (Boitani et al., 2007) are important because they can help target
1
rabies control measures (Perry, 1993) and are useful for directing dog population control
interventions (International Companion Animal Management Coalition (ICAM), 2008).
Several organizations and authors have addressed the classification of dogs based on the
different types of relationships that can exist between dogs and humans within a common
environment. In this review, I use the dog classifications proposed by the ICAM (2008), which
includes: (i) free-roaming dogs (owned and non-owned dogs without direct control and not
restricted by a physical barrier); (ii) owned dogs (those for which someone claims some right
over or states they are their property); and (iii) community dogs (those for which “more than one
individual claims ownership” of the animal). It is also important to consider that dog
classifications are not static and that dogs may move between categories (e.g. from owned dogs
to non-owned, if abandoned to the streets). Furthermore, dogs could fall under more than one
classification at one point in time (e.g. owned and free-roaming) (Boitani et al., 2007; ICAM,
2008). Characteristics of the free-roaming dog classification are discussed below.
1.3. Free-roaming dogs
According to the ICAM classification, free-roaming dogs are a combination of owned
and non-owned dogs not restricted by a physical barrier (ICAM, 2008). The free-roaming urban
dog population is made of three sub-populations: owned “pet dogs” that are allowed to roam-free
by their owners as well as lost owned dogs, non-owned dogs usually referred to as “strays”
(Rubin and Beck, 1982) and feral dogs (dogs living in a “wild and free state” without intentional
or direct food or shelter provided by people (Boitani et al., 2007)). The free-roaming “pet dog”
population includes owned dogs that are permitted to roam-free and those that escape
confinement on their owners’ property (Rubin and Beck, 1982). The amount of confinement
provided to a dog by its owner influences the dogs’ range and interactions with other dogs and
2
people (Rubin and Beck, 1982). In this context, free-roaming dogs are a global problem that
impact upon countries of all degrees of economic development, but especially developing
countries and underserved communities (e.g. indigenous communities in Canada) (Dalla Villa et
al., 2010; Shurer et al., 2015). Inadequate public sanitation and waste management systems in
these areas could increase the access and availability of food to the free-roaming dog population,
leading to an abundance of these animals (Kato et al., 2003; Fielding and Plumridge, 2005).
There are many factors that can influence the presence of free-roaming dogs on the
streets. For example, poor management of garbage (e.g. infrequent garbage disposal services,
garbage disposed of in plastic bags or in short containers) can create a source of food, which can
lead to a higher presence of free-roaming dogs (Ibarra et al., 2006). In Santiago, Chile, a higher
density of free-roaming dogs was observed in locations such as gardens and sport fields where
food was intentionally provided to dogs by people (Ibarra et al., 2006). The availability of shelter
(e.g. accessible open buildings and structures that can provide refuge to these animals) can also
increase free-roaming dog presence in communities (Ibarra et al., 2006). An understanding of the
ecological characteristics that contribute to the ability of free-roaming dogs (both owned and
stray) to persist in communities could help to identify more appropriate dog population control
strategies.
1.3.1. Owned free-roaming dog characteristics
Owned, free-roaming dogs have unique physical condition and behaviour characteristics
that differentiate them from stray, free-roaming dogs. These differences are closely related to the
bond, proximity and close connection these animals have with people, particularly their owners.
Unsurprisingly, owned, free-roaming dogs tend to be in better physical condition compared to
stray free-roaming dogs (Fox et al., 1975). A study conducted in a low-income area in St. Louis
3
Missouri, on the behaviour and ecology of a small group of urban dogs (Fox et al., 1975),
reported that owned free-roaming dogs better tolerate the proximity of people up to 4.5 to 6m; if
approached more closely, they may run away seeking shelter in places no more than 91 m away
from the place they were approached. Interestingly, a study conducted in Queens, New York
City on the ecological behaviour of owned free-roaming dogs, reported that the majority of
encounters between people and owned, free-roaming dogs are aggressive (65%) compared to
encounters with stray dogs (12%), especially when the dogs were adjacent to their homes
(territory) (Rubin and Beck, 1982). This may be because dogs perceive unfamiliar people as
intruders when near their territory. Dogs exhibiting such territory-related aggressive behaviour
(instead of a fight or flight response) might be an indication of the bond between the dog and its
owners (Rubin and Beck, 1982).
In a study conducted in a low-income area of St. Louis Missouri, owned, free-roaming
dogs were observed to exhibit peak times for activities in the morning and early evening that
corresponded with human activity (Fox et al., 1975). For example, dogs might be let out by their
owners in the morning when their owners go to work, and dogs might return home to be fed in
the afternoon when their owners arrive home from work (Beck, 1973). Owned, free-roaming
dogs were reported to travel distances of 242 meters a day, with an estimated average homerange of 0.04 km2, in a study conducted by Rubin and Beck (1982) in Queens, New York City.
Furthermore, the same study reported that the home-range for partially restrained owned dogs
(those walked on leashes or directly supervised by owners, but sometimes observed loose
without any supervision) was smaller at 0.02 km2 and larger (0.1 km2) for dogs with complete
freedom to roam (Rubin and Beck, 1982). In contrast a mean home-range of 9.3km2 was reported
for owned free-roaming dogs in an aboriginal community in coastal New South Wales, Australia
4
(Meek, 1999). There are many factors that can influence the home-range size of free roaming
dogs including, ownership status (owned vs not owned), level of confinement (in owned dogs)
(Rubin and Beck, 1982) the age, size, sex, breed, health and individual personality of the animal
(Berman and Dunbar 1983). Food availability (resources dispersion) can also be a determining
factor for the home-range size of free roaming dogs (Fox et al., 1975). Owned, free-roaming
dogs tend to travel as singles or in pairs. Larger groups of dogs have been observed around
females in heat, with a range of three to seven males (Fox et al, 1975; Pal et al., 1999). Indeed,
females in estrous might be the major reason for temporary pack formation in urban dogs (Fox et
al, 1975; Pal et al., 1999; Boitani et al., 2007).
1.3.2. Stray dog characteristics
Stray dogs are non-owned free-roaming dogs that are attracted to human settings and that
have some level of socialization, but with different degrees of fear and tolerance towards people
than owned free-roaming dogs (Boitani et al., 2007). A pilot project conducted by the World
Health Organization (WHO) in developing countries (Ecuador, Sri Lanka, Tunisia and
Zimbabwe) reported that stray dog densities ranged between 68 dogs/km2 to 3700 dogs/km2
(WHO, 1988; Brooks, 1990; Boitani et al., 2007). These dogs come from a variety of sources
including: lost owned dogs, abandoned owned dogs, or from the offspring of stray dogs
(Makenov and Bekova, 2016).
Most stray dogs are solitary, but may also roam in pairs or groups of three (Boitani et al.,
2007). Larger groups of dogs might assemble around common food sources (Boitani et al.,
2007), or around females in estrous (Pal et al., 1999; Boitani et al., 2007). Stray dogs are most
active during the early hours of the day or in the evening during cooler temperatures (Boitani et
al., 2007). They spend most of their active time scavenging for food, and may survive almost
5
entirely on human garbage, since their hunting skills tend to be lacking (Boitani et al., 2007).
Stray dogs remain close to human settings and garbage dumps, but have limited interactions with
people (Boitani et al., 2007).
Stray dogs have a shorter life expectancy than owned, free-roaming dogs, the latter of
which tend to be fed and may receive some veterinary care when hurt or sick. Life expectancy
varies from urban to rural settings. One study in Jaipur, India, found the life expectancy for stray
dogs that survive to one-year of age was estimated to be 3.8 years (Reece et al., 2008). Young
dog mortality is very high in stray dogs, with less than 20% of the puppies reaching adulthood
(one year of age) (Boitani et al., 2007). The causes of death among stray dogs are likely a
combination of malnutrition, disease, environmental exposure, predation by large predators, and
deliberate or accidental death due to human interactions (Stafford, 2007). A study in Zambia
reported that culling, disease, and car accidents accounted for 80% of the mortality in adult stray
dogs (DeBalogh et al., 1993; Boitani et al., 2007).
1.3.3. Feral dog characteristics
Feral dogs live independently in a “wild and free state” (Boitani et al., 2007), with little
to no human interaction. They often have poor physical condition (i.e. appear emaciated) and are
commonly observed with skin issues such as mange (Fox et al., 1975). Feral dogs are mostly
active at night (Boitani et al., 2007), which may minimize contact with people, as well as to
avoid exposure to excessively hot daytime temperatures (Fox et al., 1975; Boitani et al., 2007).
Feral dogs are often chased away when encountered on the streets by owned, freeroaming dogs. A study conducted in St Louis, Missouri reported that most of the interactions
between owned, free-roaming dogs and feral dogs are aggressive (Fox et al., 1975). Feral dogs
have well-defined home ranges and spend most of their life within it. Their total estimated home
6
range varies from 4.4 to 70 km2 (Boitani et al., 2007). For example, in east-central Alabama,
Scott and Causey (1973) reported a home range for feral dogs of 4.4–10.4 km2, in central Italy,
Boitani et al. (1995) reported 57.8 km2, and in Alaska, Gipson (1983) reported 70 km2. Home
range may be influenced by the availability of food (McNab, 1963; Fox et al., 1975), refuge
areas, denning areas, and other resources (Boitani et al., 2007). Many studies on feral dogs
indicate that the group size ranges from two to six individuals (Boitani et al., 2007). Group size
in feral dogs is affected by environmental conditions, the recruitment of new dogs to join the
feral dog population, and human persecution (Boitani et al., 2007). Adult feral dogs have
outstanding abilities to adapt to the urban environment, but urban conditions are not ideal for the
survival of their offspring. Limited access to nutritious food, coupled with untreated parasitic
infections and disease problems reduce the probability of offspring survival (Fox et al., 1975).
For these reasons, feral dog offspring may not contribute significantly to the total dog
abundance.
Feral dogs cannot sustain their population level without the ongoing recruitment of new
individuals from the stray dog population (Boitani et al., 2007). The recruitment of stray dogs
into a group of feral dogs often occurs during the breeding season. A study conducted in Central
Italy by Boitani et al. (1995) reported that when a single feral adult dog loses its mate, this dog
will actively co-opt another sexually mature dog, and this new member (i.e. stray dog) would
become socially accepted by the entire group of feral dogs. However, it is unclear how
generalizable this finding is (Boitani et al., 2007).
1.4. Dog overpopulation
Dog overpopulation occurs when the number of dogs exceeds the number of available
homes than can adequately care for them. Dogs are a very prolific species (Ortega-Pacheco,
7
2001). For example, in an exponentially growing population, a female dog could give rise to
67,000 individuals in only 6 years (Faulkner, 1975; Ortega-Pacheco, 2001). The global
abundance of domestic dogs is estimated to be 700 million and 75% of these may be freeroaming dogs (Macpherson et al., 2012; Hughes and Macdonald, 2013). Every year around the
world, millions of dogs are euthanized after being abandoned by their owners because they are
no longer wanted or the owners are unable to care for them (Kass et al., 2001; Davis et al., 2007;
Marsh, 2010; Yen et al., 2014). For example, in Taiwan 664,831 dogs were euthanized in dog
shelters between 1999 and 2009 (Tung et al, 2010). Despite a large number of dogs being
destroyed every year around the world, humans continue to oversee the intentional or accidental
breeding of dogs (Fennell, 1999). Many people lack an understanding of the short and long-term
consequences of dog overpopulation (Fennell, 1999). To better understand and address the cycle
of dog “production and destruction”, statistical data and adequate theoretical frameworks are
necessary (Fennell, 1999). Improved data on dog population dynamics provide a stronger
evidence-base for the design of more effective dog population control programs.
1.5. The impacts of dog overpopulation
1.5.1. Animal welfare concerns
In developing countries, the level of care for dogs may vary depending on the type of dog
(purebred or mixed-breed) (Fielding, 2010). A study conducted in Bahamas suggested that dogs
with higher monetary value might receive more direct care from humans than those of lesser
value (Fielding and Plumridge, 2005; Fielding, 2010). Dog welfare can be a difficult problem to
address in developing countries where in many places, basic human needs are not being met
(Ruiz-Izaguirre and Eilers, 2012). The inability of some dog owners to provide food and
adequate control for their dog may result in a large number of dogs being left on the streets to
8
fend for themselves. In developing countries, the number of free-roaming dogs largely exceeds
the available resources in the environment to support them (Stafford, 2007). As a result, these
animals are forced to compete with each other and with other species (e.g. free-roaming cats) for
resources (e.g. food and shelter). This situation causes many of these animals to suffer from
malnutrition, which compromises their health and reduces their likelihood of survival (Hsu et al.,
2003; Morters et al., 2014).
Free-roaming dogs are often in poor health as insufficient or lack of veterinary care
increases their susceptibility to disease (Butcher, 1999; Kwok et al., 2016). The most significant
diseases observed in free-roaming dogs include skin problems (Fox et al., 1975; Totton et al.,
2011). Other indicators of poor health observed in free-roaming dogs include lameness (Fox et
al., 1975; Totton et al., 2011) and trauma as a result of fights, or traffic accidents (Rautenbach et
al., 1991; Totton et al., 2011).
Another welfare concern related to free-roaming dogs in developing countries is the
lethal methods traditionally used to reduce their numbers (Hiby, 2013; Lembo et al., 2013;
Massei and Miller, 2013). Some of these methods include drowning, beating, starvation,
electrocution, and poisoning (Butler and Bingham, 2000; Stafford, 2007). The use of these
methods has been increasingly opposed by non-governmental, animal welfare organizations and
the general public for being inhumane and ineffective (Massei and Miller, 2013). There are
further concerns regarding the impact on the environment and non-targeted species when
poisonous chemicals are used (Hiby, 2013; Lembo et al., 2013; Massei and Miller, 2013).
1.5.2. Impact on wildlife
Domestic dogs have been introduced to all continents and most islands by humans
(Butler et al., 2004). In some places, this colonization has had a negative impact on the native
9
wildlife (Young et al., 2011), via harassment, injury, or death (Sime, 1999). For example, dogs
have been reported as predators of native fauna in the Galapagos (MacFarland et al. 1974; Kruuk
1979; Kruuk & Snell 1981; Butler et al., 2004) and the West Indies (Iverson, 1978; Butler et al.,
2004). Interactions between dogs and wildlife occur mostly in rural locations (Hughes and
Macdonald, 2013). Close contact between dogs and wildlife may also result in the introduction
of diseases to wildlife populations. For example, dogs have been implicated as the source of a
canine distemper epidemic among Serengeti lions (Panthera-leo) in 1994 (Roelke-Parker et al.,
1996; Butler et al., 2004).
1.5.3. Impact of dogs on livestock
Free-roaming dogs can have negative economic impacts on livestock and livestock
producers. Livestock mortality has been attributed to free-roaming dogs (Scott and Causely,
1973) as free-roaming, uncontrolled, and unsupervised dogs hunt for sport (Boggess et al., 1978).
A study conducted in Tierra de Fuego, Argentina reported livestock losses of $4,450,375.6
Argentinian pesos ($391,326 CAD) between 2006 and 2008, as a result of dog attacks (Zanini et
al., 2008). Hence, the harmed caused by free-roaming dogs in rural communities not only has the
potential to affect the quality of life of the people, but also their livelihood (Zanini et al., 2008).
1.5.4. Impact on environment
Free-roaming dogs can also have negative effects on the local environment and
community in which they are found. The presence of free-roaming dogs in community public
spaces can lead to negative outcomes such as the tearing of garbage bags, and the resulting litter
can attract rodents, insects, and other dogs (McCrindle et al., 1998; Butcher and De Keuster,
2013). Also, the noise produced by dog vocalization (i.e. barking) can be a nuisance to residents
within the community (McCrindle et al., 1998; Butcher and De Keuster, 2013).
10
1.5.5. Impact on public health
Free-roaming dogs also represent an important human public health concern as they are
potential vectors of zoonotic diseases (Dalla Villa et al., 2010; Butcher and De Keuster, 2013;
Garde et al., 2013). Free-roaming dogs often lack adequate veterinary care that might otherwise
address much of the risk they present for disease transmission (Garde et al., 2013). There are
over 300 recognized canine zoonoses (e.g. toxocariasis, cryptosporidiosis, salmonellosis, scabies,
Lyme disease) (Garde et al., 2013). In Latin America, the most important canine zoonoses
include rabies, leptospirosis, Chagas disease, echinococcosis, and leishmaniasis (Garde et al.,
2013). Many of these canine pathogens are shed in the feces (e.g. Echinococcus granulosus) or
urine (e.g. Leptospira) of infected animals, making fecal and urine contamination of public
spaces an important route of pathogen transmission to humans (Himsworth et al., 2010).
Rabies, a neuroinvasive disease that causes acute encephalitis in mammals, remains the
most significant zoonosis of public health concern worldwide killing between 30,000 and 60,000
people annually and dogs are responsible for the majority (75% - 99%) of all human cases in
developing countries (Garde et al., 2013, Knobel et al., 2005). The virus is most commonly
transmitted when virus-laden saliva is introduced through a bite or a scratch from a rabid animal
(Tierkel, 1975). Canine vaccination remains the most common and effective way to control
canine rabies and subsequent human infections resulting from dog bites (Schneider et al., 2005;
Cleaveland et al., 2006; Morters et al., 2013; WHO, 2013). However, in some regions, culling of
the free-roaming dog population occurs in response to canine rabies cases (Beran and Frith 1988;
Windiyaningsih et al., 2004; Morters et al., 2013). Hence, free-roaming dogs (owned, stray, and
feral) remain a concern in developing countries because of the potential transmission of rabies
and other zoonoses.
11
In addition to disease risks, dog bites and attacks are also public health and safety
concerns. The consequences of dog bites include physical injury, the psychological effects
inflicted upon the victim, permanent or temporary disability and disfigurement, as well as the
economic cost associated with medical treatment (Palacio et al., 2005; Tenzin et al., 2011). In
severe cases, dog bites and aggression can result in human death (Berzon et al., 1972; Matter and
Arbeitsgemeinschaft, 1998; Quiles et al., 2000; Palacio et al, 2005). The prevalence of dog bites
in developing countries is likely higher than estimated given that more than 50% of dog bites go
unreported (Butcher and De Keuster, 2013). In an epidemiological study of animal bites
conducted in India in 2003, 1.8% of the population reported being bitten by a dog (Sudarshan et
al., 2006; Butcher and De Keuster, 2013). In Todos Santos, Guatemala, 16.5% of surveyed
households reported that a household member had been bitten by a dog in the last 12 months
(Lunney et al., 2011). In Mexico, 116,832 dog bites were reported in 2007 (Arroyo, 2009). Many
dog bites can be prevented (Beck and Jones, 1985; Palacio et al., 2005); preventive measures
include the implementation of responsible dog ownership legislation with the major aim being to
reduce the number of dogs that are allowed to roam-free, and to ensure dogs are adequately
controlled (via a collar and leash) when exercised on public property. Other measures include
dog bite prevention education programs for children, and the improvement of dog bite
surveillance and reporting systems (Palacio et al., 2005). Due to the high number of free-roaming
dogs in developing countries, it is important for developing countries to adopt one or more dog
bite prevention strategies, including those that focus on reducing the number of free-roaming
dogs. A study conducted in Chile (Ibarra et al., 2003) indicated that the majority (43.25%) of the
reported dogs bites were caused by free-roaming dogs. However, it has been suggested that bites
12
by free-roaming dogs might be over-reported compared to bites by an owned family dog (Beck
and Jones, 1985; Beck 2000; Jackman and Rowan, 2007; Butcher and De Keuster, 2013).
1.6. Methods for estimating dog abundance
1.6.1. Owned dog abundance estimation methods
Dog abundance data are essential for the planning and monitoring of dog population
management strategies (Belo et al., 2015). Furthermore, these data can be used to identify the
number of dogs that could be at risk for a disease outbreak (e.g. rabies) (Downes et al., 2013).
There are many different methods available to estimate the abundance of owned dogs,
some of which include the assessment of veterinary records, census surveys, and sampling based
household questionnaires (Pulczer et al., 2013; Belo et al., 2015). Questionnaires are one of the
most common tools used for collecting data on owned dogs, and have been administered through
door-to-door visits, or random digit dialed telephone calls (Downes et al., 2013). The use of
door-to-door questionnaire administration for collecting data on owned dog demography and
ecology is a well-tested methodology (ICAM, 2015); however, their administration is costly and
their feasibility may be limited in large communities. Door-to-door questionnaire administration
reduces the potential for selection bias and non-response bias compared to random digit dialed
telephone calls (Downes et al., 2013). However, selection bias could be introduced when
logistical problems, such as difficult access to participants, is encountered (Butler and Bingham,
2000; Downes et al., 2013). Further, larger samples might be required in places where dog
ownership is uncommon (Knobel et al., 2008; ICAM, 2015), increasing logistical demands.
Questionnaires can be used for collecting data on a wide range of dog population
indicators (ICAM, 2015). For example, information collected about the proportion of households
that own dogs in a community and the number of dogs owned by each of those households, can
13
be used to estimate the total abundance of owned dogs in that community (Belo et al., 2015).
These questionnaires can also be used to estimate the sex distribution, age structure, mortality,
fecundity and survival of the owned dog population. The information collected by questionnaires
could then be used to plan an intervention or measure the effectiveness of an intervention once it
has been implemented (ICAM, 2015).
1.6.2. Free-roaming dog abundance estimation methods
Estimating the abundance of free-roaming dogs within a community or other defined
geographic area is an important step in understanding dog population dynamics. Estimating the
current abundance of the free-roaming dog population can be used not only for planning and
monitoring the effectiveness of interventions implemented for the welfare and control of the
free-roaming dog population (Dalla et al, 2010; Høgåsen et al., 2013; Belo et al., 2015), but to
manage the potential risk associated with the presence of these animals (Dias et al, 2013; Belo et
al., 2015). Methods used to estimate the abundance of free-roaming dogs include, census
surveys, sampling surveys based on counts, line transects, and different forms of capture and
recapture (Belo et al., 2015). The best method for estimating free-roaming dog population
abundance depends on the circumstances, the resources available, and the potential bias
associated with each technique (Belo et al., 2015). Some of the advantages, disadvantages and
bias of the methods used to estimate the abundance of free-roaming dogs are summarized in
Table 1. The ICAM (2015) advocates the use of street surveys as they are a simple method to be
used as an indicator of the free-roaming dog population density. This review focuses on the
street-survey method recommended by the ICAM (2015).
14
1.6.2.1. Street surveys
A street survey is a simple method proposed by the ICAM (2015) that can be used to
collect data on free-roaming dog indicators such as dog density, demography, and welfare
(WSPA, n.d). The data collected during street surveys relates to free-roaming dogs seen on
public property, regardless of their ownership status (ICAM, 2015). During a street survey, all of
the free-roaming dogs observed in randomly selected routes are counted and classified.
Typically, a team of two to three people follow predetermined routes in the community, slowing
or stopping to record every unconfined dog seen (dogs confined within a property, walking on a
leash or ‘close to heel’ are excluded from the survey). Every adult dog is categorized in one of
four categories: male, female, lactating female, and unknown. Body condition scoring can also
be assessed during a street survey. Five scores (emaciated, thin, ideal, overweight, and obese),
are assigned based on the fat coverage observed on the dog’s body (ICAM, 2015).
Street surveys offer some advantages compared to other methods used to estimate the
population of free-roaming dogs (e.g. sight-resight). For example, street surveys are relatively
simple and require fewer resources than, for example, a total dog population estimate study
(WSPA, n.d.; ICAM, 2015). Furthermore, street surveys can be performed repeatedly over time
to evaluate the changes in dog population size over time and after dog population control
interventions are implemented (ICAM, 2015). Street surveys also present some disadvantages.
For example, they do not produce an estimate of population size, rather they produce an indicator
that can be used to evaluate the changes in population density over time (WSPA, n.d). Another
disadvantage of street surveys that can be encountered when they are used to measure the change
in free-roaming dog population density over time is that they may be affected by urban
development (e.g. new houses being built). In street surveys, the dog count indicator may be
15
more sensitive to human: free-roaming dog ratio change than a free-roaming dog population size
estimate (WSPA, n.d.). A confounding effect can occur in street surveys when subsequent dog
counts are performed at different times of day, under different weather conditions, and by
different people. Therefore, it is important to keep these conditions the same when possible to
reduce the effect of this bias in the measured free-roaming indicator (WSPA, n.d.).
1.7. Methods to address the free-roaming dog population
Populations of free-roaming dogs can be managed in several different ways. Intuitively,
interventions are more effective when implemented in combination due to the many factors
(including cultural and social factors) that contribute to dog overabundance (OIE, 2016).
However, to ensure communities meet their management objectives, it is also important to
consider the attitude of the community members when developing effective and cooperative
approaches (OIE, 2016). Current common approaches to free-roaming dog population control are
briefly described below.
1.7.1. Education
Education on responsible dog ownership, to encourage owners to prevent their dogs from
roaming-freely, is a method that has been used to control the population of free-roaming dogs
(OIE, 2016). Since human behaviour influences the dynamics of the dog population, responsible
pet ownership education is likely the most important element of a comprehensive dog
management program (ICAM, 2008). Dog welfare, survival, and breeding are all influenced by
people’s behaviour towards dogs. Hence, education is likely to be an influential factor in the
management of dog populations (Hiby, 2013).
The main objectives of dog owner education programs are to increase responsible
behaviour in dog owners, to reduce the potential risk of zoonotic disease transmission (e.g. by
16
encouraging vaccination and parasite control in dogs), to improve dog welfare, and to improve
attitudes towards how dogs are acquired, retained, and bred (Hiby, 2013).
Veterinarians play a central role in educating the public regarding responsible dog
ownership as they are often regarded as the principal source of information on dog care by
owners. (Hiby, 2013). Animal control officers (often referred to by different names and with
different responsibilities depending on the country), could also play an important role in
educating dog owners regarding responsible ownership behaviour. This is especially true in
countries where these individuals are often the frontline workers for dog population control
programs (Hiby, 2013). An example of this is illustrated by the reduction of free-roaming dogs
taken into custody by animal control officers in Brazil after there was an increase in owner
education provided by the same officer (animal officers spoke with the owners about responsible
behaviour instead of just catching free-roaming dogs without speaking to owners) (Hiby, 2013).
The participation of animal control officers in the education of dog owners could therefore help
in the humane control of free-roaming dogs.
1.7.2. Legislation
Legislation for responsible dog ownership, which may be referred to by different names
(e.g. dog care and control bylaw), is another approach that has been used to help control the freeroaming dog population. Responsible dog ownership has been defined by the OIE (2016) as the
situation whereby a person (also defined as “more than one individual, and could comprise
family/household members or an organization”) “...accepts and commits to perform various
duties according to the legislation in place and focused on the satisfaction of the behavioural,
environmental and physical needs of a dog and to the prevention of risks (aggression, disease
transmission or injuries) that the dog may pose to the community, other animals or the
17
environment” (OIE, 2016). Responsible ownership legislation can be used to address dog
overpopulation by suggesting or mandating the sterilization of dogs, by preventing/prohibiting
dogs from roaming-freely and subsequently preventing the unintentional breeding of dogs, and in
some cases dog licensing and breeding permits for dogs (Hiby, 2013). Government agencies are
usually responsible for the elaboration and enforcement of dog ownership legislation (e.g.
vaccination, leash laws, registration, abandonment), as well as the control of free-roaming dogs
(e.g. dog catching and shelters) (Hiby, 2013). However, as Hiby (2013) points out, responsible
dog ownership needs to be enforced and implemented uniformly otherwise it will be only a
“paper exercise”. Responsible dog ownership legislation that is suitable to a given community
and enforceable is essential for the effective control of dogs (Hsu et al., 2003). Even though
legislation for responsible dog ownership has been implemented in some developed countries
with some success (e.g. Italy, Slovenia, Germany, Australia) (McMurray, 2005; Upton et al.,
2010; Hiby, 2013), this has not been the case in some developing countries. For example, a
survey conducted in Roseau, Dominica (Alie et al., 2005) where legislation (dog licensing) had
been implemented, reported poor compliance to the law, partially due to a lack of awareness of
the legislation.
Dog registration and the identification of dogs, including issuing licenses to dog owners
and breeders is another method that has been used to control the number of dogs roaming-freely
(OIE, 2016), and usually falls under legislation for responsible dog ownership. Dog registration
and identification establishes a legal link between a dog and its owner, and therefore encourages
responsible dog owner behaviour (Hiby, 2013) Dog registration and identification not only helps
reunite lost animals with owners, it can also be the basis for enforcement of dog related
legislation (e.g. mandatory vaccination) (ICAM, 2008). In developed countries, dog registration
18
is the most frequent method used to manage the dog population (Dalla Villa et al., 2010).
However, in developing countries, this method has not been widely implemented likely due to
the cost and the infrastructure that is required for such programs, as well as the higher proportion
of non-owned free-roaming dogs.
The suitability of implementing a dog ownership registration program will depend on the
use and benefits the program will bring to the community, as well as on the local attitude of
people towards dogs (Hsu et al., 2003; Stafford, 2007). For example, dog registration (licensing)
sometimes requires the payment of a fee (usually annually). A pilot study implemented in 2008
in the Philippines (Hiby, 2013), reported that some dog owners viewed the fees and penalties
imposed by mandatory dog registration to be relatively high for the local economy, and that such
high fees might encourage the abandonment of dogs and potentially reduce compliance. That
said, there have been some successful examples of registration and identification schemes. For
example, the city of Pescara in Italy has successfully implemented a registration and
identification program (Upton et al., 2010), with 70% compliance. This program resulted in a
reduction in free-roaming dogs (from 5000 dogs in 2004 to 2300 in 2008). Furthermore, it
resulted in more responsible dog ownership behaviour and a reduction in environmental
contamination due to fouling (Upton et al., 2010, Hiby, 2013).
The control of dog movements is another component of dog ownership legislation, which
helps control the dog population by limiting the access of owned dogs to public property (OIE,
2016). Controlling the movement of dogs has proven successful for some developed countries.
For example, many municipalities in Slovenia have implemented ‘leash laws’ that prohibit the
free-roaming of owned dogs in public areas. This has resulted in lower numbers of stray dogs,
and compliance rates of more than 50% (Upton et al., 2010). Therefore, restricting how owned
19
dogs can access and move within public property, could reduce the number of owned dogs
allowed to roam-free and potentially prevent unwanted litters (Hiby, 2013). However to the
author’s knowledge, no studies have been conducted to evaluate the effectiveness of this
approach in developing countries. Furthermore, implementing legislation to restrict how dogs
can move within public property may not have the same level of success in developing countries
compared to developed countries since developing countries may lack the resources to enforce
such legislation.
1.7.3. Environmental controls
Environmental controls, such as preventing dogs from accessing food sources, including
external food sources, garbage dumps, and abattoirs have also been advised for the control of
dog populations (OIE, 2016). The survival and breeding of animals is often dependent on the
level of resources (food, water, and shelter) that are available in the habitat where these animals
live. In the case of dogs, these resources are mostly controlled and supplied (directly or
indirectly) by people (Hiby, 2013). The degree to which a dog depends on resources that are
available on public property are dependent on whether the dog is owned or not, as well as the
level of care provided by its owner (if owned) (Hiby, 2013). A study conducted at the campus of
the University of Sao Paulo Brazil (Dias et al, 2013), reported that higher densities of freeroaming dogs were observed at “large organic matter generators” (e.g. university restaurants).
This study suggested that the continuous source of food was the main reason for free-roaming
dogs to be on the university campus. Restricting dog access to resources, such as garbage on
public property, would discourage scavenging and opportunistic roaming of owned dogs;
however, consideration needs to be made regarding the welfare of dogs that survive from those
resources (e.g. non-owned dogs) (Hiby, 2013).
20
1.7.4. Handling and removal of free-roaming dogs
Handling and removal of free-roaming dogs by the appropriate authorities has been a
common approach used in an attempt to control dog overpopulation (OIE, 2016). The OIE
(2016) recommends that the capture, transport, and holding of the dogs be done humanely.
Importantly, experiences in developing countries in Latin America, Asia, and Africa have shown
that the removal of free-roaming dogs has little impact on the dog population density over time,
because other free-roaming dogs immigrate to the area to replace the animals that were removed.
(WHO/WSPA, 1990; Dalla Villa et al., 2010; Hiby, 2013). Studies in other mammal species
have demonstrated that culling animals leads to the immigration of new animals to fill the places
left by those that have been removed from the population (Bolzoni et al., 2007; Woodroffe et al.,
2009, Massei, 2013). A study conducted in Guayaquil, Ecuador, reported that when free-roaming
dogs were removed from the study area, an increase in mobility (to scavenge food that had
unexpectedly become available) of the remaining dogs and of dogs from outside the area was
observed (Beran and Frith, 1988). Furthermore, the study reported that there was an increase in
the fecundity of remaining female dogs, as well as in the survival of puppies (Beran and Frith,
1988). Therefore, dog culling is unlikely to be an effective long-term control measure (OIE,
2016). The immigration of dogs associated with the process could also have further negative
impacts, including causing social unrest among the dogs, and increasing the potential for
transmission of diseases between dogs in the community, and the recently immigrated animals
(Leney and Remfry, 2000; Hiby, 2013). While dog shelters have also been considered an
important tool for the control of the free-roaming dog populations (Passantino et al., 2006),
shelters are almost exclusively found in developed countries (Dalla Villa et al., 2010).
21
1.7.5. Capture and return, re-homing, or release
Capture and return, re-homing, or release (OIE, 2016) is another approach to dog
population control. Capture and return is focused on owned dogs by capturing and returning
them to their homes or placing them under temporary shelter until they are claimed by their
owners. Capture and re-homing is focused on non-owned, free-roaming dogs. By capturing and
finding them alternative housing where they are confined, the number of non-owned dogs should
decrease. In cases where alternative housing is unavailable, capturing, neutering, vaccinating,
and releasing non-owned dogs back to where they were originally captured could, over time,
reduce the number of free-roaming dogs through attrition (Reece and Chawla, 2006; Reece et al.,
2008).
Capture, neuter and release (CNR) interventions for the control of non-owned freeroaming dogs have been used in some developing countries. CNR has proven successful for
some regions. For example, Reece and Chawla (2006) reported a 28% population reduction of
stray dogs in Jaipur, India, between November 1994 and December 2002 after 65% of the
females were sterilized and vaccinated (Reece and Chawla, 2006; Reece et al., 2008). Other
successful examples can be found in CNR programs in Abaco, Bali, Sri Lanka, and the
Galapagos (Jackman and Rowan, 2007). However, the success of CNR in these locations could
have been attributed to the minimal risks of migration of unsterilized dogs into the area. Further
studies are necessary to determine the acceptability of such interventions among community
members, the capacity at which CNR needs to be maintained, and the possible nuisance and risk
these animals still pose to people in the community (Dalla Villa et al., 2010).
22
1.7.6. Reproductive control
Reproductive control is another method of dog population control that works by
preventing the birth of unwanted puppies. Common types of reproduction control include:
surgical sterilization, chemical sterilization, and chemical contraception (each further discussed
below), as well as confinement of female dogs during estrus (OIE, 2016; ICAM, 2008; Rojas et
al., 2011). Different dog characteristics (e.g. owned free-roaming, non-owned free-roaming)
must be considered when selecting a reproductive control approach. The advantages and
disadvantages of both surgical and nonsurgical approaches for reproductive control also need to
be evaluated to ensure they are socially and culturally accepted by the community before
implementation (Massei and Miller, 2013).
1.7.6.1. Surgical sterilization
Traditional surgical sterilization remains the most commonly used strategy for pet
contraception in developed countries (Howe, 1999); however, surgical sterilization services may
be less available in developing countries, considering that surgical sterilization requires skilled
veterinary doctors (Jana and Samanta, 2007). Any service to control the reproduction of dogs
needs to be affordable, accessible, and sustainable (Hiby, 2013). For these reasons, surgical
sterilization services should be developed locally with the veterinary capacity so that these
services can be sustainable. It has been suggested that surgical sterilization may be at first costly,
but is expected to become more cost-effective over time compared to lethal methods of dog
population control (Hiby, 2013). Affordable and less invasive methods of dog reproduction
control are necessary for dog population management programs to be feasible in developing
countries. Early-age sterilization (i.e. surgical sterilization performed in both male and female
dogs between 6 and 16 weeks old; Root-Kustritz, 2014) is an approach used to increase the
23
effectiveness of population control measures, since this strategy sterilizes the animals before they
reach puberty (Howe, 1999), thus preventing the birth of unplanned litters. Sterilizing dogs
before they have the opportunity to mate and have litters can reduce the cost and improve the
effectiveness of dog population control programs (Di Nardo et al., 2007).
1.7.6.2. Non-surgical contraception
Contraception in dogs can be achieved through chemical reproductive control, which
prevents pregnancy by temporarily or permanently sterilizing these animals (Kutzler and Wood,
2006; Munson, 2006). There are several non-surgical contraceptive methods that can be used to
inhibit reproduction, including: hormonal methods, immunocontraceptives, and chemosterilants
(Massei and Miller, 2013).
Steroidal hormones (e.g. progestins, estrogens, and androgens) administered via oral
tablets or by parenteral injections, have been used as reproductive inhibitors in owned dogs
(Rojas et al., 2011; Alliance for Contraception in Cats and Dogs (ACC&D), 2013; Massei and
Miller, 2013) and have the ability to temporarily control the reproduction of female dogs by
delaying their estrous cycles. Other hormonal methods are based on Gonadotropin-releasing
hormone (GnRH) agnostics (proteins that act like GnRH and stimulate the production and
release of Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH)). These methods
can postpone puberty in both sexes and can also control the reproductive cycle (Romagnoli et al.,
2009; Rojas et al., 2011; Massei and Miller, 2013). Among GnRH agonists, deslorelin
(Suprelorin, Virbac), can postpone estrus in female dogs for up to 27 months and suppress
reproduction in male dogs for at least a year (Trigg et al. 2001). Deslorelin is currently registered
only for use in male dogs in Australia and Europe (Massei and Miller, 2013). Another GnRH
agonist is azagly-nafarelin (Gonazon, Intervet International B.V.). Gonazon can induce at least
24
1-year reversible contraception in female dogs and prevent puberty in young female dogs for at
least 1 year with no side effects observed (Rubion et al, 2006). When used in male dogs,
Gonazon has shown to decrease the concentration of testosterone for at least 6 months
(Goericke-Pesch et al, 2010). Gonazon is currently approved in the European Union, but has not
been yet brought into the European Union market (Massei and Miller, 2013).
Inmunocontraceptive vaccines are another option and work by inducing antibody
production against proteins or hormones essential for reproduction and therefore, can prevent
pregnancy (Miller et al., 2009; McLaughlin and Aitken, 2011; Massei and Miller, 2013). GnRHbased vaccines (different than GnRH agnostics), target GnRH and prevent ovulation and
spermatogenesis. Zona pellucida (ZP)-based vaccines inhibit egg–sperm binding and
fertilization. These vaccines are commonly used for population control in wildlife species but
may have additional application for the control of domestic dog populations. GonaCon is a
GnRH-based vaccine, recently registered as a contraceptive for white-tailed deer, horses, and
feral donkeys in the United States (Killian et al., 2008; Miller et al., 2008; Massei and Miller,
2013). This product was shown to induce infertility for at least 1 to 6 years after a single
injection (Massei and Miller, 2013). GonaCon has not yet been proven effective in dogs;
however, early trials of ZP-based vaccines in dogs have shown promising results (Massei and
Miller, 2013). Early formulation of GonaCon tested in dogs “showed abscesses and draining at
the injection site after the injection” (Massei and Miller, 2013). A new formulation has since
been produced and tested in a pilot study carried out on captive dogs in Mexico (Massei and
Miller, 2013; Vargas-Pino et al., 2013). This new formulation did not result in abscesses at the
injection sites. Currently GonaCon is not commercially available for dogs; however, the US
Department of Agriculture Animal and Plant Health Inspection Service are actively investigating
25
the licensing, manufacturing and distribution of this product (Massei and Miller, 2013).
Chemosterilants have been developed as an alternative to surgical castration in male
dogs. These drugs are injected into the testicles (epididymis or vas deferens) causing sterility via
sclerosis of the testes (Massei and Miller, 2013). Zinc gluconate has been approved in Mexico,
Colombia, Bolivia, Panama, and the United States, as a chemical castration drug for male
puppies aged 3 to 10 months (Massei and Miller, 2013). An advantage to chemical sterilization
is that general anesthesia is not required which is potentially advantageous because it reduces the
technical expertise required for deployment in developing countries. However, sedation is
currently recommended to prevent movement of the dog during injection. Proper injection
technique is critical to prevent complications such as ulceration of the scrotum and painful
swelling of the testes (Massei and Miller, 2013). For this reason, adequate training is necessary,
which could affect its feasibility, implementation, and sustainability, especially in less resourced
settings. Further, this drug does not completely eliminate testosterone; therefore, male dog
behaviours such as roaming, marking, aggression, or mounting may still be exhibited (Kutzler
and Wood, 2006; Massei and Miller, 2013). The use of chemosterilant in male dogs is an
attractive option because it removes the disadvantages and costs of surgical sterilization and
post-operative care (Rojas et al., 2011). Furthermore, in regions where surgical castration of
male dogs is not culturally accepted (e.g. Romania, the Bahamas) chemical castration offers a
reasonable alternative (Fielding et al, 2002; Cocia and Rusu, 2010; Garde et al., 2016). Hence,
chemical castration could be an attractive option for developing countries with limited resources
for surgical dog management programs (Garde et al., 2016).
Non-surgical sterilization methods could provide a cost-effective, humane alternative to
surgical sterilization in areas where surgical interventions are not widely accessible (Massei and
26
Miller, 2013). Furthermore, non-surgical sterilization could provide short-term population
control while a community works to increase the number of dogs surgically sterilized. However,
the cost and effectiveness of larger scale applications of non-surgical sterilization interventions
still needs to be evaluated. Computer simulation models present a novel methodology for
informing the potential effectiveness of both surgical and non-surgical dog population control
interventions without incurring the cost of implementation and of scaling up. Computer
simulation models could offer insight on whether non-permanent, non-surgical sterilization
procedures are effective and/or cost-effective for dog population control in circumstances where
dogs might need to be captured to undergo the procedure multiple times.
1.8. Mathematical modeling and simulation
Models are tools that allow for the exploration and evaluation of a variety of different
model configurations in order to better understand a specific problem. Models are simplified
descriptions of real systems, processes, or phenomena expressed in mathematical terms (Grimm,
1999; Addo, 2012). They are useful in that they can provide insight into potentially effective
and/or optimal strategies and reduce the amount of complex experimental and/or fieldwork
required to address a specific research question (Allman and Rhohes, 2004; Addo, 2012; Dürr
and Ward, 2015). However, models cannot precisely and explicitly reconstruct actual events.
Consequently, reasonable considerations need to be made regarding model expectations and
outcomes (Christley et al., 2013). Models cannot be classified as “true or false models”; all
models are inherently “false” to some degree. However, models can be classified as ‘useful’ and
‘not useful’ based on the intended purpose and use of the developed model. Sensitivity analysis,
the study of how the uncertainty of a model output may depend on the uncertainty in the model
input elements (Saltelli and Sobol, 1995; Saltelli et al., 2010), can be used to help develop a
27
“comfort level” with predictions obtained from a particular model (Frey and Patil, 2002). That is,
it can help in evaluating how robust the model output is to the model input assumptions (Frey
and Patil, 2002). The purpose of a model determines its structure and for this reason, there can be
an infinite number of models created; all of these may be potentially useful for the context within
which they were developed (Bolker et al., 1997; Uchmanski and Grimm, 1997; Grimm, 1999).
1.8.1. Population dynamic models
Population dynamics is the applied study of populations as functioning systems
(Solomon, 1976). This discipline explores changes in population abundance and the factors that
influence those changes. It looks into the loss and replacement of members in a population, and
at any factors that regulate these processes (e.g. reproduction, mortality, immigration, and
emigration) through density dependent feedbacks. Population dynamics considers the influence
that members of the population have on each other (i.e. favourable or adverse, direct or indirect),
as well as the influence the environment exerts upon the population (Solomon, 1976). Population
dynamics have been heavily studied and researched (Murray, 2002; Lande et al., 2003; Turchin,
2003; Chavas, 2015), and population models based on mathematical equations are commonly
used in population ecology as a tool to better understand population dynamic processes (Holmes,
1994; Faust et al., 2004) and develop management plans for species of interest (Morris and
Doak, 2002; Lande et al., 2003).
The main purpose of models in population ecology is not to predict changes of specific
populations, but rather to provide a general understanding of how biological processes, including
those that are driven by individual behaviour, can affect population change over time (Berec,
2011). Population dynamic models can be used to explain population fluctuations, as well as to
project future population abundances under hypothetical scenarios (Newman et al., 2014). They
28
can also serve as a scientific basis to guide management actions for implementation (Yoder et al.,
2008), and have proven useful for predicting the consequences of management actions (e.g.
habitat modifications or predator removal; Newman et al., 2014). Quantitative models of
population dynamics have been an indispensable tool for the conservation and management of
endangered and threatened wildlife species (Beissinger and Westphal 1998; Beissinger and
McCullough, 2002; Morris and Doak, 2002; Faust et al., 2004). Population dynamic models have
also been used to described domestic dog populations and to evaluate different strategies for their
control (Table 2).
Many mathematical approaches have been used to develop quantitative models of
population dynamics. These approaches include matrix algebra (e.g. Leslie matrices), differential
and partial differential equations, system dynamics, and agent-based (individual-based) models.
This review briefly covers agent-based models, which was the modelling approach used in this
thesis.
1.8.2. Agent-based models
Population projections can be particularly difficult to make in populations with complex
social structures, such as in those where individuals contribute differently to the population
depending on their social role (Stenglein et al., 2015). For example, in the case of dog
populations, a dog’s individual characteristics (e.g. sex, age), and behaviour (e.g. free-roaming)
will determine the contribution of each individual dog to the overall population dynamics (e.g.
reproduction, mortality, immigration, and emigration). Therefore, incorporating these individual
characteristics and behaviour into the model can help describe the dog population dynamics
more realistically. Individual-based models can be used to explicitly model individual
differences, which can lead to a more realistic population model (Stenglein et al., 2015).
29
Agent-based modeling, also referred to as individual-based modeling, is a powerful computer
simulation technique that emerged in the 1970s to complement differential equation based
models (McLane et al., 2011). Agent-based models (ABMs) consist of a collection of
autonomous agents with defined individual dynamic behaviours. Agents are the basic and most
fundamental unit in ABMs (Chen, 2012), and can be the same type (homogenous) or different
from each other (heterogeneous) (Billari et al., 2006). Agents can interact with each other and
with the environment they share (Parunak et al., 1998; Kreft et al., 2001; Bonabeau, 2002; Billari
et al., 2006; Vincenot et al., 2011). ABMs describe a system from the point of view of its basic
units, the agents (Bonabeau, 2002).
ABMs are popular in many scientific fields because of their ability to describe complex
systems. ABMs are generally easier to conceptualize than population-based models (e.g. system
dynamic models) because they require less abstraction (summarized information regarding a
population, for example the mean of a characteristic of the population) (Osgood, 2009; Stenglein
et al., 2015), although they also have been criticized for being so complex that the systems
modeled are impossible to understand (Topping et al., 2010). The goal of agent-based modeling
is to improve understanding of the processes in a system and not to provide a precise
representation of such system (Billari et al., 2006). Even simple ABMs can reveal complex
patterns of behaviour and provide important information about the real-world systems they
emulate (Bonabeau, 2002). In ABMs, the levels of description or complexity and aggregation
can be modified (scaled). For example, one can start with a simple model given the available
data and then add complexity as data accumulates (e.g. more agents or agent characteristics can
be added to the model) (Bonabeau, 2002).
30
ABMs offer several benefits over other modeling techniques. For example, ABMs can be
especially useful for spatially explicit problems because agents can interact dynamically in
multidimensional spaces (e.g. 2D or 3D) (Kreft et al., 2001; Vincenot et al., 2011). ABMs also
capture emergent phenomena. Emergent group behaviour can be deduced from the interactions
among autonomous agents that follow simple rules (Bonabeau, 2002). ABMs also provide a
natural description of a system and offer a more detailed way to describe what is happening in
the real world (Bonabeau, 2002). ABMs are also flexible, as their level of description or
complexity and aggregation can be modified (Bonabeau, 2002). ABMs have special value in
evaluating the impact of interventions where the population in the system displays high
heterogeneity, clustering, or complex and dynamic network structures, as well as where such
characteristics are likely to impact the interventions being evaluated (Osgood, 2009). Lastly,
ABMs can provide a more realistic, visual model output making them easier to communicate to
stakeholders and end-users in a way that is more intuitive compared to other modeling
approaches, such as differential equations (Axtell, 2000; Billari et al., 2006).
Unfortunately, ABMs also have challenges and limitations. Model likelihood (i.e.
parsimony) cannot be evaluated in ABMs, especially for model applications that describe
complex adaptive systems in which system behaviour emerges from individual behaviour and
local interaction (Laine, 2006). ABMs need sufficient data to appropriately parameterize the
models (Van der Vaart et al., 2016) and can present computational challenges. Specifically,
simulations of large synthetic populations with many attributes may require far more time and
computer memory to run model-based experiments than aggregate models (Osgood, 2009).
Furthermore, ABMs frequently require significantly greater time to be understood and analyzed
than aggregate models (Osgood, 2009). These challenges can lead to reduced realism and
31
generalizability (e.g. less likely to be able to extrapolate the model results to other sites and/or
time periods) (Van der Vaart et al., 2016).
ABMs have been used in population ecology since the 1970s, (Grimm, 1999), to study
the relationships between species, their population dynamics, and to understand how “animals
perceive, learn and adapt to their habitat” (DeAngelis and Mooij, 2005; McLane et al., 2011).
ABMs have been increasingly used in population ecology to answer pragmatic questions, to
explore ecological theory (Grimm and Railsback, 2005), and to recreate and simulate synthetic,
biological systems (Wilensky and Rand, 2015; Ireland and Miller, 2016). ABMs have also been
used to evaluate the effectiveness of population management options (Grimm et al., 2005;
McCarthy et al., 2013; Miller et al., 2014; Ireland and Miller, 2016).
1.8.3. Applications of population dynamic models
Several mathematical modeling approaches have been used to understand population
dynamics and to evaluate population management strategies in wildlife (Niven, 1970; Zarnoch
and Turner, 1974; Rohner, 1996; Haight and Mech, 1997, Vucetich et al., 1997; Haight et al.,
1998; Vucetich and Creel, 1999; Harding et al., 2001; Haight et al., 2002; Pitt et al., 2003; Ellis
and Elphick, 2007; Conner et al., 2008; Stenglein et al., 2015). While mathematical models have
been applied to domestic cat populations (Courchamp and Cornell, 2000; Andersen et al., 2004;
Foley et al., 2005; Short and Turner, 2005; Budke and Slater, 2009, Lohr et al., 2013; Miller et.
al., 2014; Ireland and Miller, 2016), only a small number of mathematical models have been
published to describe the population dynamics of domestic dogs (owned and stray) and to
evaluate different strategies to control their populations (Frank, 2004; Di Nardo et al., 2007;
Amaku et al., 2009; Amaku et al., 2010; Totton et al., 2010; Baquero et al., 2016; Yoak et al.,
32
2016). A brief description of the models related to domestic dog populations is provided in
Table 2.
Agent-based modeling could be used to more realistically describe domestic dog
population dynamics compared to other approaches such as differential and partial differential
equations. To the author’s knowledge, agent-based modelling has only been used to describe
stray dog populations in the peer-reviewed literature (Table 2). Agent-based modeling and
simulation could be a powerful tool to help better understand how individual-level heterogeneity
can affect the population dynamics of owned dogs, and how such heterogeneity could affect the
proposed population control measures. This modeling tool could be particularly useful for
studying dog population dynamics in developing countries, where the characteristics and
behaviours of the dogs are highly heterogeneous. This tool could also potentially help inform the
design and planning of more cost-effective dog management programs for developing countries.
2. Thesis rationale and objectives
The overabundance of dogs in developing countries poses significant public health,
animal health, and animal welfare concerns. A thorough understanding of the ecology and
demographic characteristics of a dog population are essential for planning and monitoring dog
population control programs. Currently, little data exist regarding the demography and dynamics
of owned dog populations in semi-urban areas (i.e. areas with 10,000 to less than 15,000
residents) in Mexico. Typically, these communities are characterized by a lack of infrastructure
for the provision of public services (INAP, 2009), including animal control services. In these
communities, understanding owned dog ecology and demography can help inform the strategic
use of limited resources for the effective control of the dog population. Computer simulation
models that integrate dog ecology and demography data could help determine the potential
33
impact of interventions for controlling and/or reducing the size of the dog population in these
communities.
Villa de Tezontepec is one of the 84 municipalities in the state of Hidalgo, in centraleastern Mexico. The municipality has an estimated human population of 11,746, (National
Institute of Statistics and Geography (INEGI), 2010) and the municipal government estimates
over 2000 people visit this community every weekend. The municipal government of Villa de
Tezontepec consulted with the Ministry of Health regarding their dog overpopulation concerns.
This thesis was conducted to better understand the local dog population situation and evaluate
the impact of different interventions for dog population control in this community. The primary
objectives of this thesis were:
1) To characterize the dog ecology and demography in Villa de Tezontepec, Hidalgo,
Mexico (Chapter 2).
2) To develop an agent-based model to describe the population dynamics of owned dogs in
Villa de Tezontepec, and to use the model to characterize the projected impact of surgical
reproduction control interventions (focused on dogs of different ages and with varied
surgical capacity) and improved dog confinement, on the total dog population size over
time (Chapter 3).
3. Format of the thesis
This thesis has been written in a journal manuscript format. Chapter 1 is a summary of
the relevant literature, and Chapters 2 and 3 are stand-alone manuscripts that contain the
following sections: abstract, introduction, methods, results, discussion, references, tables and
figures. The conclusion in Chapter 4 summarizes the research and results of Chapter 2 and 3, and
provides directions for future research. Supplementary information is presented in the Appendix.
34
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Table 1. Advantages, disadvantages, and biases associated with methods used to estimate the abundance of free-roaming dogs.
Method
Census
Surveys
Sampling
Surveys
Line transects
Capture/sightrecapture/
re-sight
studies. (e.g.
LincolnPetersen
estimator,
Method of
Beck et al.)
58
Advantages, disadvantages, and bias
Census surveys involve counting “all” free-roaming dogs observed in a determined area; however, since free-roaming
dogs have varying behaviour and different degrees of tolerance towards people, they will have different probabilities
of being captured.
Disadvantages: Census surveys are only applicable if “all” the free-roaming dogs could be captured at the same time
(or within a short period of time) in the whole area under study (Belo et al, 2015). For these reasons census surveys
should only be used for closed and small populations of free-roaming dogs, and when they can be implemented
within a short period of time (Belo et al, 2015). Census surveys need to be conducted alongside calibration procedures
and statistical tests for the presence of heterogeneities of detection probabilities, since this method does not account
for differences in animal detection (Belo et al, 2015).
Sampling surveys involve counting free-roaming dogs that belong to sampling units that represent the area under
study, in which all the free-roaming dogs can be counted or the sampling fraction can be estimated (Belo et al, 2015).
Disadvantages: Implementing a sampling survey can be as complex as a census survey (Belo et al, 2015).
Advantages: Sampling surveys are cheaper when large areas are covered (Belo et al, 2015).
The line transect method, involves observing free-roaming dogs along transects located in the study area to estimate
the density of these animals in the area.
Bias: Bias could be potentially introduced in this method if the distances between the transects and the dogs are not
adequately measured or if transects are not arranged randomly in the area surveyed (Belo et al, 2015).
Capture/sight-recapture/re-sight studies involve capturing and marking or identify (e.g. digital photographs) the
number of free-roaming dogs seen in an area during a first count, then recording what percentage of those dogs are
recapture or seen during a second count of the same area. The percentage of the marked or identified dogs not seen on
the second count provides an estimate of the percentage of dogs that are not visible on any one count (WSPA n.d.)
Disadvantages: Failing to identify dogs as result of the use of inadequate marks or photographs (Belo et al, 2015).
Capture/sight-recapture/re-sight studies need to be implemented within short time intervals to prevent losing the
animal markers, and to be able to assume homogeneous probabilities of capture to be able to produce unbiased
estimates of the dog population size.
Advantages: If photographs are used to identify the dogs, this removes the need for physical contact between the
researcher and the dogs (Belo et al, 2015).
Table 2. Mathematical models used to describe domestic dog population dynamics and to evaluate different strategies for dog
population control. Information in the table includes dog population of interest, study location, model methodology used, and model
USA
Location
A mathematical model based on the basic
demographic equation (Hinde, 1998)
A generalized population flow model,
which included economic and ecological
factors in both human and dog populations
Model Methodology
“To understand the dynamics of canine overpopulation
and the effectiveness of various policy options for
reducing euthanasia”
Model Objective
Frank (2004)
Reference
objective.
Italy
“To determine how the female dog sterilization rate
can affect the owned dog population of the province of
Teramo, Italy”
“To simulate dog population dynamics with
sterilization and euthanasia”
Population of
Interest
Owned and stray
dogs
Owned dogs
Brazil
Yoak et al.
(2016)
Baquero et al.
(2016)
Totton et al.
(2010)
Amaku et al.
(2010)
Amaku et al.
(2009)
Di Nardo et al.
(2007)
Stray dogs
“To predict the long-term impact of the current
sterilization rates on the dynamics of the stray dog
population over time”
“To improve the knowledge of dog population
dynamics and to facilitate the evaluation of population
management interventions”
“To estimate the effectiveness and effects of
sterilization on the reduction of the canine population
density”
Brazil
India
Logistic growth model based on a coupled
system of differential equations
Stray dogs
Stray dogs
Brazil
Agent-based model
Deterministic mathematical model based
on a set of differential equations resolved
numerically by fourth-order Runge-Kutta
method
Deterministic mathematical model based
on a set of differential equations resolved
numerically by fourth-order Runge-Kutta
method
A stochastic mathematical model based on
a set of differential equations.
Owned and stray
dogs
India
Stray dogs
“To build a demographically accurate and spatially
explicit agent-based model of a large free-roaming dog
population to investigate how to maximize the impact
of dog management”
59
CHAPTER TWO
Owned dog ecology and demography in Villa de Tezontepec, Hidalgo, Mexico.
Published in Preventive Veterinary Medicine (Kisiel et al., Prev Vet Med 2016; 135: 37-46)
Abstract
Dog overpopulation in developing countries has negative implications for the health and
safety of people, including the transmission of zoonotic diseases, physical attacks and
intimidation to humans and animals, as well as impacts on canine welfare. Understanding the
ecology and demographic characteristics of a dog population can help in the planning and
monitoring of canine population control programs. Little data exist regarding demography and
dynamics of domestic dog populations in semi-urban areas in Mexico. A cross-sectional study
was carried out between October 21 and November 7, 2015, to characterize the dog ecology and
demography in Villa de Tezontepec, Hidalgo, Mexico. A face-to-face survey was used to collect
data from randomly selected households in four contiguous communities using stratified twostage cluster sampling. Within each household, adults answered questions related to their dogs
and their experiences with dog bites and aggression. A total of 328 households were interviewed,
representing a participation rate of 90.9% (328/361) and 1,450 people. Approximately 65.2% of
the households owned one or more dogs, with a mean of 1.3 (SD = 1.5) and 2.0 (SD = 1.5)
owned dogs in all participant households and dog-owning households, respectively. The human:
owned dog ratio for all participant households was 3.4:1 (1450/428), and for the dog-owning
households was 2.3:1 (984/428). The owned dog male: female ratio was 1.4:1 (249/179).
Approximately 74.4% (95.0% CI = 69.8% – 78.7%) of the owned dogs were older than one year
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(mean age: 2.9 years; SD = 2.5). The mean age of owned female dogs at first litter was 1.9 years
(SD = 1.2) and the mean litter size was 4.2 puppies (SD = 2.1). Approximately 36.9% (95.0% CI
= 31.8% – 46.4%) of the females were spayed, and 14.1% (95.0% CI = 10.7% – 19.7%) of the
males were neutered. Only 44.9% (95.0% CI = 40.1% – 49.7%) were always confined when
unsupervised. Approximately 84.4% (95.0% CI = 80.6% – 87.7%) were reported to have been
vaccinated against rabies in 2015. The knowledge of owned dog demography and ecology
provided by this study can inform local government planning of dog population control
interventions, and could serve as a baseline for the development of agent-based models to
evaluate the effects of different dog population control strategies on dog demography.
KEYWORDS: Mexico, dog demography, domestic dog, canine overpopulation, population
management, survey questionnaire.
1. Introduction
Inadequate control of dog populations can have grave consequences for public health and
the welfare of dogs (Stafford, 2007). Dogs can transmit several important zoonotic diseases to
humans, including rabies, leishmaniasis and echinococcosis (Garde et al., 2013). Dogs also
remain the main reservoir and vector of rabies to humans worldwide (Wunner and Briggs, 2010;
Chomel and Arzt, 2013). It is estimated that canine rabies is responsible for 55,000 human deaths
worldwide every year (Knobel et al., 2005). In Mexico, there have been no reported cases of
human rabies transmitted by domestic dogs since 2006 (Secretaria de Salud, 2015c); however, 12
cases of canine rabies were confirmed during 2012 (Dyer et al., 2014), therefore the threat for
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rabies transmission to humans remains. Even in the absence of disease, dog bites are a major
public health problem in Mexico, with 116,832 reported cases of dog-to-human bites in 2007
(Arroyo, 2009). Dogs can also cause other problems including physical aggression and
intimidation towards humans, noise and fouling, livestock predation, wildlife endangerment, and
road traffic accidents (ICAM, 2008; Hiby, 2013, Pulczer et al., 2013).
It is estimated that the global abundance of domestic dogs is 700 million and 75% of
these may be free-roaming dogs (Hughes and Macdonald, 2013). Government efforts to reduce
dog population density in developing countries tend to focus on culling (Beran and Frith 1988;
Windiyaningsih et al., 2004) and sterilization (Reece and Chawla 2006, WHO, 2013). New
approaches to non-surgical sterilization, such as chemical castration in males, have also been
tested and continue to be investigated (Jana and Kumar, 2007; Levy et al., 2008; Oliveira et al.,
2012).
An understanding of dog demography, ecology and dog ownership practices and
behaviours can help inform the planning, implementation and monitoring of appropriate dog
population management and zoonotic disease control programs (WHO, 1987; WHO/WSPA,
1990; Perry, 1993; Patronek and Rowan, 1995; Acosta-Jamett et al., 2010; Morters et al., 2014)
and estimates of dog abundance can help project the cost and resources needed for population
control interventions (Wandeler, 1985). This is especially important when resources are limited.
Data collected in dog demography and ecology studies can also serve as a baseline against which
comparisons can be made after an intervention has been implemented to measure its
effectiveness (ICAM, 2015). Information on dog population dynamics such as birth and
mortality rates and demographic data such as age and sex distributions can also be used to inform
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mathematical models that can be used to simulate population growth and control activities and
help quantify the expected effects of interventions (Coleman, 1997).
Limited data currently exist regarding domestic dog population demography and
dynamics in semi-urban areas in Mexico. There have been only a few studies on dog
demography in urban and rural areas; these include Mexico City, (Romero-Lopez et al., 2008),
Mexicali, Baja California (Flores-Ibarra and Estrella-Valenzuela, 2004), Merida, Yucatan
(Ortega-Pacheco et al., 2007) Atlixco, Puebla (Fishbein et al., 1992) and Miacatlan, Morelos
(Orihuela and Solano, 1995). To the authors’ knowledge, there have not been any published
studies focused on semi-urban communities (i.e. areas with 10,000 to less than 15,000 residents)
in Mexico (INAP, 2009). Currently there are 262 semi-urban municipalities in Mexico (INFDM,
2010a), which are typically characterized by a lack of infrastructure for the provision of public
services (INAP, 2009), including animal control services. Therefore, it is important to understand
dog ecology and demography in semi-urban communities in Mexico because this knowledge will
inform strategic investment of resources and use of limited infrastructure for more effective dog
population control programs.
Villa de Tezontepec is one of the 84 municipalities in the state of Hidalgo, located in
central-eastern Mexico. The municipality covers an area of 133.6 km2 and has an estimated
human population of 11,746 based on the 2010 National Institute of Statistics and Geography
(INEGI) census (INEGI, 2010). The municipal government of Villa de Tezontepec estimates that
every weekend over 2000 people come to eat Baracoa, the regional dish (sheep slow-cooked in a
hole dug in the ground covered with Agave leaves); these weekly events may increase the
contact between people and the free-roaming dog population of this community, raising the
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potential risk of dog bites and transmission of zoonotic diseases. The municipal government of
Villa de Tezontepec consulted with the Ministry of Health regarding their dog overpopulation
concerns. The present study was conducted to better understand the local situation. The specific
objective of this study was to characterize the ecology and demography of the owned dog
population in Villa de Tezontepec, Hidalgo, Mexico.
2. Materials and methods
A cross-sectional study was conducted in Villa de Tezontepec, Hidalgo, Mexico, between
October 21 and November 7, 2015. The University of Guelph Research Ethics Board approved
the involvement of human participants in this study (Protocol #15JL005).
2.1. Questionnaire survey design
A household questionnaire was designed and modified from Pulczer et al. (2013) and the
Guide to Monitoring and Evaluating Dog Population Management Interventions (ICAM, 2015
pp. 115–120). Part A of the questionnaire focused on household information, including questions
about the age and gender of household members, number of dogs owned per household, number
of dogs that died or left the household in past 12 months, reasons for not owning dogs, and plans
to acquire a dog. Part B of the questionnaire focused on individual owned dog information and
included questions about each dog’s age and sex, sterilization (i.e. spay or neuter), vaccination
and confinement statuses, sources of the dog, reasons for owning the dog, female dog
reproductive history, and whether a dog had ever bitten a person or another dog. An “owned”
dog was defined as a dog for which a person, during the household questionnaire administration,
stated that they owned and could answer questions about the dog’s sex and age, as well as
provide knowledge of the dog’s life. No formal pre-testing of the questionnaire was conducted
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for the present study; however, pre-testing was done for a questionnaire that was used in
Guatemala (Pulczer et al., 2013) and which served as the basis of the questionnaire used here.
The questionnaire was written in English and then translated into Spanish by the principal
author, who is a native Spanish speaker; local government collaborators also reviewed the
Spanish translation of the questionnaire prior its use. A copy of the questionnaire in English
(Appendix A.1 and Appendix A.2) and Spanish (Appendix A.3 and Appendix A.4), respectively,
is included in Appendix A.
2.2. Study region and neighbourhood selection
The municipality of Villa de Tezontepec lies between latitudes 19 ° 53' north latitude and
98 ° 49' west longitude, at an altitude of 2.3 meters above the sea (INFDM, 2010b). Tezontepec,
the capital and center of day-to-day activities in the municipality of Villa de Tezontepec, and
three contiguous neighbourhoods (Colonia Morelos, Colonia Benito Juarez, and Chamberluco)
were selected as the study region, as they were located next to the capital. Other neighbourhoods
were excluded from the study region because they were either relatively far from the capital
(range: 1.9 to 8.6 km) or because the number of households was relatively small (range: 5 to 288
households).
2.3. Household selection
A sample size of 328 households was calculated for this study, based on an expected
prevalence of 50% (households owning at least one dog), 5% allowable error and 95%
confidence (Flores-Ibarra and Estrella-Valenzuela, 2004; Ortega-Pacheco et al., 2007; RomeroLopez et al., 2008). Anticipating 10% refusal to participate, this sample size was increased to
361 households out of the total 2249 occupied households reported in the 2010 national census
65
(INEGI, 2010), the most recent census available.
Multistage sampling was used, where the primary sampling unit was blocks within
neighbourhoods, and the secondary sampling unit was households within blocks.
The probability proportional to size sampling (PPS) technique described by Inner City Fund
(ICF) International (2012) was used at the first stage to randomly select a sample of blocks
within each neighbourhood. Blocks were defined as “a geographical space of polygonal shape
and variable surface, comprised of one or more households, shops, or vacant lots” (INEGI,
2007). The required number of blocks was calculated by dividing the required sample size
(n=361 households) by a fixed number of households to be surveyed per block, agreed to be 8
households, based on study logistics and the perceived maximum number of households a
questionnaire administrator could reasonably interview in a day. A total of 46 blocks was
required. We used information from the national household inventory from the INEGI to
construct the sampling frame (total of 174 blocks). All blocks in the sampling frame were listed
and numbered sequentially based on a geographic pattern, starting from west to east and moving
north to south, and the total number of households in each block was recorded. A list of the
cumulative number of households per block was then created, producing a total 2249
households. A sampling interval (49) was calculated by dividing the total cumulative number of
households (n=2249 households) by the primary sampling unit (n=46 blocks). A random number
equal to or less than the calculated sampling interval (49) was selected using a computer random
number generator (www.random.org). This randomly chosen number was then located within the
list of cumulative households and the identified block was determined to be the first block
selected. Every 49th household in the cumulative household list was sequentially selected
66
thereafter to randomly select blocks until all the 46 blocks were selected.
For sampling in the second stage, eight households per block were selected using simple
random selection and the random number generator. The household selection started at the
southeast corner of the block then moved counterclockwise around the block for all the blocks. If
a randomly selected household was a business or was unoccupied, the neighbouring occupied
household on the right was selected.
2.4. Door-to-door household survey
The study was promoted in Villa de Tezontepec several days before the survey began, via
printed posters and social media networks to encourage participation. Both dog-owning and nondog-owning households were included in the study. Within each sampled household, the person
(18 years of age or older) at home and most able to answer questions related to dogs and their
care (if the household owned dogs) was asked to participate in the survey. If no one was home at
a selected household, it was revisited twice more on different days and at different times of day.
If no one was home on these subsequent visits, the household was considered a refused
household.
Survey administrators attended a 3-hour training session on the survey methodology.
Survey administrators included 25 students from the Veterinary College of the Autonomous
University of the State of Hidalgo and 5 students from the National College of Professional
Technical Education, 5 local volunteers, and 4 members of the Ministry of Health Zoonosis and
Rabies Prevention Program in Tizayuca.
The household questionnaires were administered orally in Spanish. Informed oral consent
was obtained from all participants prior to starting the questionnaire. Data were recorded by the
67
survey administrators directly on individual hard copies of the questionnaire. At the end of each
data collection day, the survey administrators gave the questionnaires to the lead author to be
entered in an electronic database.
2.5. Owned dog density
The area of the study region and the area for each neighbourhood were calculated in
square kilometers using the polygon tool in Google Earth Pro for Mac (Google Inc., 2015) by
drawing a perimeter connecting the most external households in each neighbourhood (Belsare
and Gompper, 2013). The predicted owned dog abundance for the study region and for each
neighbourhood was calculated by multiplying the number of households in each area by the
proportion of dog-owning household and then by the mean number of owned dogs per area. The
dog population density was calculated by dividing the predicted owned dog abundance in the
study region and per each neighbourhood by its calculated area, respectively.
2.6. Data analysis
Collected questionnaire data were entered into a custom-made online database made in
ODK (Open Data Kit) Collect version 1.3, and uploaded into Formhub (Modi Research Group,
Columbia University, NY). Data entry was validated by visually comparing the data against the
original questionnaire responses for accuracy. All entered data were then uploaded into an
Excel® file (Microsoft Corporation, 2010). Descriptive statistics (means, standard deviations,
medians, ranges, proportions, and 95% confidence intervals) and Fisher’s exact chi-square
statistics to compare proportions were performed using STATA/SE for Mac (StataCorp LP,
2015).
68
3. Results
3.1. Survey participation and household characteristics
Individuals residing in 328 households were interviewed in the study region (15.0% of
the total identified households across the four selected neighbourhoods), representing a
household participation rate of 90.9% (328/361); and a total of 1450 household residents. Out of
all the respondents asked to participate, female participation (73.0%; 239/328;) was higher than
male participation. Details on participating household characteristics are described in Table 1.
3.2. Dog ownership
Approximately two-thirds of households (65.2%; 214/328; 95% CI = 60.0% - 70.2%)
reported owning one or more dogs, for a total of 428 dogs. The calculated surface area for the
study region was 4.69 km2; therefore, the estimated absolute owned dog density was 623 owned
dogs/km2. Details on the number of owned dogs, human: owned dog ratios, and estimated
absolute density per neighbourhood are described in Table 2.
Of the 114 participating households that did not own dogs, 31.6% (36/114; 95% CI =
23.2% - 40.9%) reported that they did not own a dog because they did not like dogs, 39.5%
(45/114; 95% CI = 30.4% - 49.1%) did not have space for a dog, and 22.8% (26/114; 95% CI =
15.5% – 31.6%) indicated that a dog required too much time, work, and/or money (multiple
reasons allowed per participant). One hundred thirteen non-dog owning households answered a
question of whether they planned on acquiring a dog in the next 12 months; 87.6% (99/113; 95%
CI = 80.0%- 92.6%) reported they had no such plans.
69
3.3. Owned dog demographics
3.3.1. Age, Sex and Spay/Neuter Status
Of 428 owned dogs, 58.2% (249/428; 95% CI = 53.4% - 62.8%) were male, producing a
male to female ratio of 1.4:1 (249/179). The age and sex structure of the owned dog population is
listed in Table 3, and displayed in an age pyramid Figure 1. The majority (94.7%) of dogs were 3
months of age or older, and 74.4% (294/395; 95% CI = 69.8% - 78.7%) were older than one
year. The mean age of owned dogs was 2.9 years (SD = 2.5; median: 2 years, range: newborn to
15 years). Only 14.1% (35/249; 95% CI = 10.7% - 19.7%) of the males were reported as
neutered and 36.9% (66/170; 95% CI = 31.8% - 46.4%) of the females were reported as spayed
(Table 3, Figure 1). Female dogs were significantly more likely to have been sterilized than male
dogs (Fisher's exact test, p < 0.0001). Out of all reported surgically altered dogs, 80.0% (76/95;
95% CI = 70.6% - 87.0%) were sterilized during subsidized government spay/neuter clinics,
16.8% (16/95; 95% CI = 10.5% - 26.0%) were sterilized by private veterinarians; three owners
reported not knowing where their dog was spayed or neutered. Reasons reported by dog owners
for not spaying or neutering their dogs are listed in Table 4.
3.3.2. Owned dog mortality
A total of 36 dogs from all dog-owning households were reported to have died or have
been killed in the 12 months prior to the survey; reasons included old age, disease, hit by a car,
killed by someone, starvation, and intentional poisoning. The number of males and females
among dogs that died was the same (18 and 18, respectively) and the mean age was 3.9 years
(SD = 4.3; median: 2 years; range 0.2 years to 13 years).
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3.3.3. Reproductive indices and litter survivorship
Among the owned female dogs, 5.4% (9/167 responses; 95% CI = 2.8% - 10.1%) were
pregnant at the time of the survey, and 26.4% (37/140 responses; 95% CI = 19.7% - 34.4%) had
been pregnant in the previous 12 months. Among female dogs that had been pregnant in the
previous 12 months, 73.0% (27/37; 95% CI = 55.8% - 85.3%) had 1 litter, 5.4% (2/37; 95% CI =
1.3% - 20.3%) had 2 litters, and 21.6% (8/37; 95% CI = 10.8% - 38.5%) did not provide
information regarding the number of litters during this time. More than half (58.0%; 21/37; 95%
CI = 39.5% - 72.9%) of owned female dogs that had been pregnant in the past 12 months were
bred intentionally. The reasons reported by dog-owning households for intentionally breeding
their female dog(s) included: wanting to sell the puppies (50.0%; 6/16; 95% CI = 25.0% 75.0%), “for my dog’s health and needs” (31.1%; 5/16; 95% CI = 12.2% - 59.8%), wanting more
dogs (12.5%; 2/16; 95% CI = 2.6% - 43.0%), and wanting a male dog (6.3%; 1/16; 95% CI =
0.7% - 39.3%). Five households did not provide reasons for intentionally breeding their female
dog.
The mean age of an owned female dog at first litter was 1.9 years (SD = 1.2; median: 1.5
years; range 0.7 years to 6 years). The mean number of live pups born per owned female dog was
4.3 (SD = 2.0; median: 4; range: 1 to 9). Information obtained on last litter revealed a total of 97
puppies, of which 5 puppies from 2 different litters were stillborn, yielding a stillborn risk of
5.2% (5/97; 95% CI = 1.7% - 11.6%). The overall mean number of litters in the past 12 months
reported per female was 0.22 (SD = 0.45; median: 0; range 0 to 2). The litter male to female
ratio was 1:1.
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3.4. Owned Dog Ownership Patterns
Of 411 owned dogs for which we had data, 26.5% (109/411; 95% CI = 22.5% - 31.1%)
had been acquired in the past 12 months. The sources of dogs reported by dog-owning
households are described in Table 5 and included: gift (having someone give the household a
dog at no cost), adopted (from a dog rescue organization or an animal shelter), pup of owned
dog, bought, found (on the street), and other sources. The mean age of a dog when it was
acquired was 0.4 years (SD = 0.7; median: 0.3 years; 0 years to 6 years).
Of the 428 reported owned dogs for which reasons for ownership were provided
(multiple responses per participant were allowed), approximately two-thirds (68.9%; 295/428;
95% CI = 64.3% - 73.3%) were owned for companionship as pets, 30.1% (129/428; 95% CI =
25.8% - 34.7%) for guarding, 2.1% (9/428; 95% CI = 1.0% - 4.0%) for breeding, 1.4% (6/428;
95% CI = 0.5% - 3.0%) for herding/protecting livestock, 0.2% (1/428; 95% CI = 0.0% - 0.2%)
for pest control; one dog was reported as having “arrived by himself”.
3.5. Dog management and handling practices
Almost half (44.9%; 184/410; 95% CI = 40.1% - 49.7%) of the owned dogs were
described as “always confined” when unsupervised; the remainder were allowed to roam-freely
unsupervised during all or part of the day (Table 6). Only 35.4% (101/285; 29.9% - 41.3%) of
the reported intact owned dogs (both female and male over 6 months) were described as
“confined” at all times.
More than half (58.3%; 238/408; 95% CI = 53.5% - 63.0%) of the owned dogs were
reported to be walked by their owners; of these, roughly one-third (34.7%; 74/213; 28.4% 41.5%) were reported to be walked on a leash. Almost all (97.8%; CI = 95.8% – 98.9%) of the
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owned dogs were fed at least once a day.
The proportion of owned dogs reported to have ever bitten a person or another dog was
3.4% (14/409; 95% CI = 2.0% - 5.7%) and 12.5% (51/408; 95% CI = 9.6% - 16.1%),
respectively. Approximately 84.4% (342/405; 95% CI = 80.6% - 87.7%) of all owned dogs were
reported to have been vaccinated against rabies in 2015. The rabies vaccination male to female
ratio was 1.4:1 (199 to143, respectively). The proportion of vaccinated male dogs was not
significantly different than vaccinated female dogs (Χ2 =1.5, p= 0.5). The proportion of owned
dogs reported to have been dewormed in the past 12 months was 67.9% (275/405; 95% CI =
63.2% - 72.3%).
4. Discussion
This study describes the dog ecology and demography of the owned dog population in
Villa de Tezontepec, Hidalgo, Mexico. This information can be used in the effective design of
targeted humane dog population programs in Mexico and potentially, other developing countries.
It could serve the local government as a baseline against which comparisons can be made after
an intervention has been implemented to measure intervention effectiveness (ICAM, 2015). This
information could also be used to inform mathematical models for the simulation of population
control activities that can help quantify the expected impact of an intervention (Coleman, 1997).
Dogs are very popular pets in Mexico (Ortega-Pacheco et al., 2007). Several studies in
developing countries (e.g. Guatemala, Brazil, Chile, Peru) report that dog-owning households
account for half or more of all the households studied (Davlin and VonVille, 2012). The
proportion of dog–owning households reported in this study was 65.2% and is comparable with
other studies performed in Mexico: 42.7% - 56.4% in Mexico City (Romero-Lopez et al., 2008);
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54.0% in Mexicali, Baja California (Flores-Ibarra and Estrella-Valenzuela, 2004); 73.0% in
Merida, Yucatan (Ortega-Pacheco et al., 2007); 73.9% in Atlixco, Puebla (Fishbein et al., 1992)
and Central and South America: 51.0% in Guatemala (Pulczer et al., 2013); 52.5% in São Paulo,
Brazil (Alves et al., 2005); 57.0% in Villa del Mar, Chile (Morales et al., 2009); 58.2% in San
Martin de Porres, Lima-Peru (Arauco et al., 2014). Knowledge of the size of the owned dog
population can be used to help determine the number of resources that might be required for
reproduction control interventions within communities.
Similarly, the human: owned dog ratio in our study (3.4:1) is comparable to ratios
reported in other Mexican studies, in both urban and rural communities: 2.6:1 in Miacatlan,
Morelos (Orihuela and Solano, 1995); 3.4:1 in Atlixco, Puebla (Fishbein et al., 1992); 3.4:1 in
Merida, Yucatan (Ortega-Pacheco et al., 2007); 4.0-6.0:1 in Mexico City (Romero-Lopez et al.,
2008); and 4.3:1 in Mexicali Baja California (Flores-Ibarra and Estrella-Valenzuela, 2004). It
should be noted that several of these studies either did not provide, or used different definitions
of “owned dog” than the present study; this has implications for direct comparisons of study
results. Our definition was very restrictive and therefore might have underestimated the number
of owned dogs compared to studies that used a less restrictive definition. In the present study, the
interviewed households with dogs reported having 1 to 8 dogs, with a mean in dog-owning
households of 2.0 dogs. This is also consistent with reports in Guatemala (1.6) (Pulczer et al.,
2013), Brazil (1.6) (Alves et al., 2005), Peru (1.6) (Arauco et al., 2014), and Mexico (1.6 - 2.1)
(Ortega-Pacheco et al., 2007; Orihuela and Solano, 1995).
The mean age of owned dogs in our study was 2.9 years, which is consistent with
previous reports: 2.7 years in San Martin de Porres, Lima-Peru (Arauco et al., 2014); and 3.1
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years in Merida, Yucatan, Mexico (Ortega-Pacheco et al., 2007); but notably lower than the
mean age of 4.6 years reported in Villa del Mar, Chile (Morales et al., 2009). Age is one of the
most impactful characteristics in population modeling, as individuals have different reproduction
and survival characteristics at different ages (Li and Brauer, 2008), and sterilization of dogs at
different ages has different affects on the dog population growth (Di Nardo et al., 2007).
Dog ecology studies in developing countries, have commonly reported that the sex ratio
favours male dogs (Orihuela and Solano, 1995; Kongkaew, et al., 2004; Suzuki et al., 2008;
Arauco et al., 2014). Our study is not the exception, with a male: female dog ratio of 1.4:1. Dog
owners may believe that male dogs make better guard dogs (Kitala et al., 2001), and in contrast,
that female dogs tend to attract free-roaming males during estrus, as well as produce unwanted
puppies (Hsu et al., 2003). We speculate that born unwanted female dogs might be abandoned on
the streets, sold or given away, but we are unable to confirm this.
Intact free-roaming female
dogs, abandoned or otherwise, are likely to impact the dog population dynamics and they should
be the focus of the dog population control programs (Jackman and Rowan, 2007).
Surgical sterilization (neutering of males and spaying of females) has been generally
accepted as a vital part of humane population control programs (Leney and Remfry, 2000).
Female dogs (36.9%) in our study had a significantly higher proportion of sterilization than male
dogs (14.1%). The relatively high proportion of sterilized dogs and the higher proportion of
sterilized females over males described by our study are comparable with estimates previously
reported in Italy (8.0% males; 30.0% females) (Slater et a., 2008) and Brazil (17.0% males;
23.0% females) (Baquero et a., 2015); but differ from estimates reported in Bolivia (26.0%
males; 7.0% females) (Suzuki et al., 2008); Mexico (5.8% males; 3.8% females) (Orihuela and
75
Solano, 1995); Kenya (15.0% males; 0.0% females) (Kitala et al., 2001); and Guatemala (9.2%
males; 0.0% females) (Pulczer et al., 2013). One of the reasons for observing a lower proportion
of sterilized males dogs compared to females dogs could be due to owners’ attitudes against male
dog castration. In Mexico “virility is a cultural symbol” (Stevens, 1965) characterized by the
ideology that males should have valour, strength and courage, as well as sexual potency beyond
normal levels (Stevens, 1965; Andrade, 1992). These beliefs remain strong especially in more
rural communities. Male dogs may be less likely to be sterilized because male owners of male
dogs may experience “anthropomorphic empathy regarding emasculation” and fear that
protective behaviours in male dogs might be removed or decreased by castration (Blackshaw and
Day, 1994; Martins-Soto et al., 2005; Levy et al., 2008). However, lack of knowledge regarding
the benefits of male dog sterilization and the availability of male dog sterilization services could
also result in lower numbers of male dogs being sterilized. For example, a spay and neuter
program conducted in El Paso County along the US-Mexico border reported almost equal
numbers of male and female dogs being sterilized. Several factors influenced the increase in pet
owners participation in that program, including promotional and educational activities prior to
the sterilization event, as well as affordability and accessibility of the services. Hence, education
of male dog owner regarding benefits of sterilization may have led to increased uptake of the
sterilization services (Poss and Bader, 2008). Dog reproduction control approaches need to be
evaluated during the planning stages to ensure they are socially and culturally accepted by the
community before they are implemented (Massei and Miller 2013). For example, educational
efforts focused on altering negative attitudes towards male sterilization could be implemented
76
prior to an intervention. These efforts increase the likelihood that the proposed intervention will
succeed (Fielding et al., 2002).
Approximately 80.0% of sterilized dogs in this study were reported to have been
sterilized during government subsidized spay/neuter clinics. The reason for the higher proportion
of altered dogs seen in our study compared to the others studies, may be due to government
subsidized services of pet sterilization offered in the State of Hidalgo and all its municipalities,
including Villa de Tezontepec. The Ministry of Health in Mexico provides spay and neuter
services at no cost for both male and female dogs and cats, from six weeks of age (Secretaria de
Salud, 2015b). Despite high uptake overall, only a small proportion of owned dogs younger than
six months were spayed or neutered (2.9% (1/35) males, 0.0% females). This may be due to a
lack of awareness among dog owners of the availability and benefits of early age sterilization
(i.e. between the ages of 6 and 16 weeks), including the reduction of reproductive behaviours
such as roaming, urine marking, sexual aggression, and the decreased risk of mammary tumors
and pyometra in female dogs, and testicular tumours in male dogs (Root-Kustritz, 2014). Despite
the availability of early spay and neuter services in the study area, this service appears to have
been under-utilized.
In our study, 26.4% of the non-spayed female dogs were bred in the past 12 months,
which differs from what has been reported elsewhere (for example, 37.5% in Merida, Yucatan,
Mexico (Ortega-Pacheco et al., 2007); 50.9% in Antananarivo, Madagascar (Ratsitorahina et al.,
2009); and 54.0% in the Machakos District, Kenya (Kitala et al., 2001)). Out of female dogs that
were bred, 58.3% were bred intentionally and the most common reason for this decision, as
described by their owners, was that they would like to sell the offspring (50.0%). The mean litter
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size per owned female dog was 4.2 puppies, which is consistent with other studies (for example,
3.7 pups per litter was reported in Antananarivo, Madagascar (Ratsitorahina et al., 2009), 5.0 in
Villa del Mar, Chile (Morales et al., 2009), and 5.2 in the Machakos District, Kenya (Kitala et
al., 2001)). Dog owners that obtain a financial gain from breeding their dogs, even if the gain is
small, will be less likely to participate in dog reproduction control initiatives such as spay and
neuter initiatives (Fielding, 2010). Unregulated backyard breeding of dogs plays an important
role in the overpopulation of dogs (Fielding and Plumridge, 2005). Knowledge of the proportion
of female dogs that are intentionally bred and that might not participate in dog reproduction
control initiatives can be used to assess the potential effectiveness of dog population
interventions in the long term. Further research is needed regarding the economic and cultural
motivation of backyard breeding in this community. Investing in educational interventions to
create public awareness on the dog overpopulation problem should also be considered.
In our study, only 18.2% of owned dogs were purchased either from internal or external
sources such as dog owners, stores, markets, and veterinary clinics. Almost half (47.7%) of the
owned dogs in our study were acquired as a gift (i.e. given to the dog-owning households from
households within or outside the study region at no cost). This finding is similar to other studies
in developing countries (for example, 36.0% in Antananarivo, Madagascar (Ratsitorahina et al.,
2009); 56.0% in the Machakos District, Kenya, (Kitala et al., 2001); and 57.2% in Merida,
Yucatan (Ortega-Pacheco et al., 2007)). In the present study, the questionnaire did not
distinguish “gifts” (i.e. just being given to someone at no cost) versus “true gifts” (i.e. given to
someone as a surprise or to celebrate a birthday or holiday). When dogs are given to someone at
no charge, they can end up with owners that lack a genuine interest in caring responsibly for
78
them, and such dogs could eventually be relinquished or abandoned on the street (New et al.,
2000; Fielding, 2010). However, studies have reported that dogs received as “true gifts” have a
lower risk of relinquishment compared to dogs acquired from other sources (Weiss et al., 2013).
Having a dog for companionship was the main reason (68.9%) reported for dog ownership in this
study; this is similar to what has been reported in Mexico City (55.4% to 69.8%) (Romero-Lopez
et al. 2008). In contrast, our result is higher than that reported in dog ecology studies in Chile
(42.4%) (Morales et al., 2009) and Merida, Yucatan (49.4%) (Ortega-Pacheco et al., 2007). Dogs
can be an emotional and social support to their owners (Ramírez et al., 2014), and an alternative
to human affection, especially for older adults (Lagoni et al., 1994; Kurdek, 2008; Ramírez et al.,
2014). A high proportion of dogs owned for companionship may be associated with a high
number of older adults in the population. When planning for dog reproduction control
interventions such as spay and neuter services, consideration should be given to make sure these
services are accessible to older adults and their pets.
The percentage of owned dogs kept confined varies between developing countries. Our
study revealed that 44.9% of dog-owning households kept their dogs confined at all times when
unsupervised. This is lower than Mexico City, Mexico (54.6% and 58.3%) (Romero-Lopez et al.,
2008), Brazil (60.7%) (Alves et al., 2005), Guatemala (68.5%) (Pulczer et al., 2013), and Villa
del Mar, Chile (77.5%) (Morales et al., 2009). A high number of owned free-roaming dogs could
have a negative impact on human health and safety, including the potential transmission of
zoonotic diseases, physical aggression towards humans, fouling, livestock predation, wildlife
endangerment, and road traffic accidents (ICAM, 2008; Hiby, 2013). Further, unaltered owned
dogs that are allowed to roam-freely, could contribute to dog overpopulation as a result of
79
unplanned pregnancies and unwanted litters (Fielding, 2010). Further research is warranted to
understand the reasons dogs are allowed to roam-freely in this community. This may help in the
development of applicable and enforceable responsible pet ownership legislation.
The World Health Organization (WHO) recommends that at least 70.0% of the dog
population be vaccinated against rabies and that the vaccination status be maintained to achieve
control and eventual elimination of canine rabies (Coleman and Dye, 1996; Cleaveland et al,
2003; WHO, 2013). In Latin America, in 2005, the mean rabies vaccination coverage was
reported to be 68.0% (OPS, 2005). In Mexico, the rabies vaccination coverage reported between
2001 and 2003 was higher than 80.0% in most parts of the country (OPS, 2005). Other studies in
Mexico report different levels of vaccine coverage, for example in Miacatlan, Morelos (90.6%)
(Orihuela and Solano, 1995); in Merida Yucatan (90.1%) (Ortega-Pacheco et al., 2007); in
Mexicali Baja California (73.0%) (Flores-Ibarra and Estrella-Valenzuela, 2004) and in Mexico
City (39.8% -47.4%) (Romero-Lopez et al., 2008). Our study shows that in Villa de Tezontepec,
84.4% of the owned dog(s) were reportedly vaccinated against rabies during the government
anti-rabies vaccination campaign in 2015. The Ministry of Health carries out a rabies vaccination
campaign each year in the months of March and September. Each campaign has a duration of
seven days. During each event, owned cats and dogs receive a rabies vaccine from trained
personnel and volunteers. Vaccines are given to pets either as a part of a door-to-door campaign
or in fixed vaccination booths at no cost to pet owners (Secretaria de Salud, 2015a). Our study
data were collected during the months of October and November; therefore, we are reporting the
government anti-rabies vaccination coverage for 2015. Subsidized dog rabies vaccination
programs increase vaccine coverage rates (Durr et al., 2009). A limitation of the government
80
vaccination program is that it may only be owned dogs that are vaccinated (Secretaria de Salud,
2015a); high proportions of owned dogs vaccinated against rabies might not indicate that the
level of control and protection against rabies have been reached as non-owned, unvaccinated,
free-roaming dogs still pose a risk for the transmission of canine-mediated rabies. Further studies
to estimate the abundance of non-owned, unvaccinated, free-roaming dogs is necessary to better
assess the total dog population vaccination coverage level in this community.
5. Limitations
Several limitations of the study should be noted. Owned dog demography studies only
play a partial role in the true understanding of the “total dog population” ecology and
demography; information on the non-owned dog population would be useful, but was not
possible in the present study. The four neighbourhoods included in the study were sampled
based on their proximity to the capital. These neighbourhoods may be more highly populated and
have higher household density than the other neighbourhoods in Villa de Tezontepec. As stated
earlier, the questionnaire was translated from English to Spanish by native Spanish speakers.
However, we noticed during survey administration that a few words may have been
misinterpreted by the respondents during the survey application. For example, we noticed that
the proportion of dogs reported as “adopted” was unexpectedly high (14.4%), suggesting that
adoption as the source for owned dogs may have been chosen by the respondent over other
options also presented on the questionnaire. The word ‘adoption’ was intended to describe dogs
that were adopted from a humane society or similar institution, but local people may have
understood that adoption meant getting a dog from the street (found on the street, an option
provided in the questionnaire), or getting a dog from another household owner (received as a
81
gift, also an option provided in the questionnaire). As a result, we may have underestimated the
proportion of dogs acquired as gifts and found stray on the street. Another example where a
word could have been misinterpreted is the word “gift”, as described above. As a result, we may
have overestimated the number of dogs that may be at a higher risk of relinquishment.
6. Conclusions
In conclusion, more than half (65.2%) of the households in Villa de Tezontepec owned
dogs. The majority (84.4%) of owned dogs were vaccinated against rabies in 2015, less than half
(44.9%) of these dogs were kept confined when unsupervised, and only a small proportion were
spayed or neutered. The knowledge of owned dog demography provided by this study allows for
the description of demographic indicators that could be used by the local government for the
planning, implementation, and monitoring of effective dog population control interventions. The
data collected in this study could serve the local government as a baseline against which
comparisons can be made after an intervention has been implemented to measure intervention
effectiveness. These data can also be used to build a dog population agent-based computer
simulation model to assess the potential impact of different control programs in this, and similar,
populations.
7. Conflict of interest statement
The authors declare that they have no conflicts of interest.
8. Acknowledgements
The authors would like to thank: Health Services of the State of Hidalgo, particularly to
Dr. Maria Concepcion Carmona, Dr. Jesus Alfredo Castillo, Dr. Luis Rene Gress, Dr. Laura
Hernandez and Dr. Mario de Jesus Rodriguez, for their support of this research study; the mayor
82
of Villa de Tezontepec, Mrs. Amalia Valencia and the municipal government for supporting the
study; the Faculty of Veterinary Medicine of the Autonomous University of Hidalgo and
participating undergraduate students for assistance with surveys administration, especially to Dr.
Ignacio Olave; the students of National College of Professional Technical Education
(CONALEP) in Villa de Tezontepec for their participation in survey administration; the local
volunteers for their exemplary participation, cooperation and hospitality, especially, Mrs. Lorena
Orozco for her logistic support; Mr. Wayne Johnston (University of Guelph) for his assistance in
the creation of a custom-made online database for the data entry; Mrs. Lucrecia Quiroz for her
assistance during the entry of the data collected; and all the households in Villa de Tezontepec
who participated in this study. The authors gratefully acknowledge Mathematics of Information
Technology and Complex Systems (MITACS) Globalinks Award (IT05893) and the Canada
Research Chairs Program for funding, as well as in-kind funding provided by Health Services of
the State of Hidalgo. The study sponsors had no involvement in the study design, in the
collection, analysis and interpretation of data; in the writing of the manuscript; or in the decision
to submit the manuscript for publication.
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Table 1. Number of people categorized by age, median number of people per household, median age of people per household, and
Benito Juarez
Morelos
Tezontepec
1 (3.6)
27 (7.2)
17 (8.4)
41 (5.2)
< 5 years
Children
115 (8.3)
4 (14.3)
40 (10.7)
13 (6.4)
58 (7.3)
5 – 9 years
Children
212(15.2)
3 (10.7)
60 (16.1)
41 (20.3)
108(13.7)
10 – 17 years
Children
705 (50.6)
8 (28.6)
183 (49.1)
99 (49.0)
415 (52.5)
18 – 50 years
Adults
275 (19.7)
12 (42.9)
63 (16.9)
32 (15.8)
168 (21.3)
≥ 50 years
Adults
4.0
3.5
5.0
4.0
4.0
per household
Median # of people
32
48
27
32
36
age
Median
1.0:1.0
1.2:1.0
1.1:1.0
1.0:1.0
0.9:1.0
Ratio
Male to Female
Neighborhood
Chamberluco
86 (6.2)
The table does not include missing age data for 57 people
TOTAL
male to female ratio in 328 households in 4 neighborhoods surveyed in Villa de Tezontepec, Hidalgo, Mexico, 2015a.
a
94
Table 2. Mean, median and range of number of dogs per dog owning household, the human to owned dog ratio, the estimated total
number of owned dogs and the estimated absolute owned dog density for four neighbourhoods surveyed in Villa de Tezontepec,
Hidalgo, Mexico, 2015.
Owned dogs
Estimated
Mean #
Number of
Dogs
Dogs/km2)
Owned
per Dog-
to
Households
465
Predicted
Owned dogs
#
Owned
1651
2566
Human
Percent of all
owning
People
3.6
359
1666
Dog
among DogHouseholds
1270
0.1
915
111
Owned
owning
Median
3.3:1.0
307
0.6
50
623
Area
households
Households
(range)
827
4.8:1.0
613
0.5
2924
#
that owned
(SD)
1 (1 - 8)
211
3.0:1.0
59
4.7
Density
dogs
2.0 (SD = 1.5)
1 (1 – 8)
384
3.1:1.0
2249
Dogs
64.6 (126/195)
1.8 (SD = 1.6)
1 (1 -7)
28
3.4:1.0
(km2)
248
51.1 (24/47)
2.3 (SD = 1.4)
1 (1 – 3)
1450
Owned
Tezontepec
44
73.1 (57/78)
1.3 (SD = 0.8)
1 (1 – 8)
Neighbourhood
Morelos
127
87.5 (7/8)
2.0 (SD = 1.5)
(# Owned
Benito Juarez
9
65.2 (214/328)
Abundance
Chamberluco
428
dog ratio
OVERALL
95
Table 3. Age, sex, and spay/neuter structure of the owned dog population, in Villa de Tezontepec, Hidalgo, Mexico, 2015. (n=428
Adult 3 to 5 years
Adult Under 3 years
Juvenile 6 to 12 months
Juvenile 3 to 6 months
Puppy (under 3 months)
Unknown
41 (9.6)
122 (28.5)
117 (27.3)
50 (11.7)
30 (7.0)
21 (4.9)
33 (7.7)
# (%)
Total Owned Dogs
10 (4.0)
21 (8.4)
73 (29.3)
64 (25.7)
32 (12.9)
21 (8.4)
14 (5.6)
14 (5.6)
# (%)
Male Owned Dogs
179 (100.0)
4 (2.2)
20 (11.2)
49 (27.4)
53 (29.6)
18 (10.1)
9 (5.0)
7 (3.9)
19 (10.6)
# (%)
Dogs
Female Owned
35 (14.1)
2 (20.0)
8 (38.1)
16 (21.9)
6 (9.4)
2 (6.3)
1 (4.8)
0 (0.0)
0 (0.0)
# (%)
Owned Dogs
Neutered Male
66 (36.9)
3 (75.0)
12 (60.0)
21 (43.8)
23 (43.4)
3 (17.7)
0 (0.0)
0 (0.0)
4 (21.1)
# (%)
Owned Dogs
Spayed Female
dogs)
Adult 6 to 10 years
14 (3.3)
249 (100.0)
Age Group
Adult over 10 years
428 (100.0)
TOTAL
96
Table 4. Reasons reported by dog owners for not spaying or neutering their owned dogs, in Villa
de Tezontepec, Hidalgo, Mexico, 2015.
Percent of Owner
Reasons for Not Spaying/Neutering
Responses
Owned Dog(s)
# (%)c
“Do not know”
38 (17.9)
Do not know what is involved or how to get it done
31 (14.6)
Want to breed to sell offspring
27 (12.7)
Transportation/scheduling problems
26 (12.3)
“To keep it in good health”
25 (11.8)
Risk of the surgery/suffering of dogs
25 (11.8)
Too expensive/do not have the money right now
13 (6.1)
Otherd
27 (12.7)
TOTAL
212 (100.0)
c
Calculated as: number responses per particular reason /total number of reasons provided.
d
Other owner-reported reasons include: 1) Too young (48.5%; 16/33), 2) Dog does not go out
(12.1%; 4/33), 3) There is no spay/neuter campaign (6.1%;2/33), 4) I have not done it (6.1%;
2/33), 5) He/she does not need it (6.1%; 2/33), 6) I have not thought about it (3.0%; 1/33), 7)
Carelessness (3.0%;1/33), 8) There was a campaign but she was pregnant (3.0%;1/33), 9) I do
not want it (3.0%; 1/33), 10) I want him to be a dad (3.0%; 1/33), 11) I want a male dog (3.0%;
1/33), 12) I want him to mate (3.0%; 1/33).
97
Table 5. Sources of owned dogs in Villa de Tezontepec, Hidalgo, Mexico, 2015. (n=411 dogs)g
Percent of Owned Dogs
Source of Owned Dog
# (%)h
Gift from inside Villa de Tezontepec
138 (33.6)
Adopted
59 (14.4)
Gift from outside Villa de Tezontepec
58 (14.1)
Pup of owned Dog
52 (12.7)
Bought from outside Villa de Tezontepec
39 (9.5)
Bought from owner inside Villa de Tezontepec
32 (7.8)
Found
24 (5.8)
Bought from a store inside Villa de Tezontepec
4 (1.0)
Otheri
5 (1.2)
TOTAL
411 (100.0)
g
Table does not include 17 missing responses.
h
Calculated as: number of owned dogs in a type of source /total number of owned dogs reported.
i
Other sources include, 1) Veterinary Clinic 6.7% (1/ 6) and 2) Do not know 83.3% (5/6).
98
Table 6. Percent of owned dogs by confinement frequency category, in Villa de Tezontepec,
Hidalgo, Mexico, 2015. (n=410 dogs)j
Percent of Owned Dogs Confined
Time of Confinement
# (%)k
Always
184 (44.9)
Never
143 (34.9)
Night
36 (8.8)
Daylight
29 (7.1)
“Sometimes”
17 (4.2)
“Do not know”
1 (0.2)
TOTAL
410 (100.0)
j
Table does not include 18 missing responses.
k
Calculated as: number of owned dogs in a confinement frequency category/total number of
owned dogs reported.
99
Adultover10years
Adult6to10years
Adult3to5years
AdultUnder3years
Juvenile6to12months
Juvenile3to6months
Puppy(under3months)
Unknown
30%
Unaltered Male
10%
10%
Spayed Female
20%
30%
Unaltered Female
Female Dog Population Percentage
0%
100
Neutered Male
Male Dog Population Percentage
20%
Figure 1. Age population pyramid of owned dogs, in Villa de Tezontepec, Hidalgo, Mexico, 2015.
AgeCategories
CHAPTER THREE
Modeling the effect of surgical sterilization and confinement on owned dog population size
in Villa de Tezontepec, Hidalgo, Mexico, using an agent-based computer simulation model
Prepared for submission to Preventive Veterinary Medicine
Abstract
In addition to animal welfare concerns, the uncontrolled growth of a dog population can have a
negative impact on public health and safety. Surgical sterilization programs have been proposed
as an intervention to help control the size of dog populations. Simulation models can be used to
help determine the long-term impact of dog reproduction control interventions. The objective of
this study was to determine the projected impact of surgical sterilization interventions (focused
on dogs of different ages and with varied surgical capacity) and increased dog confinement (not
allowing dogs to roam-free) on total owned dog population size in Villa de Tezontepec, Hidalgo,
Mexico. A stochastic, agent-based simulation model was constructed and parameterized using a
combination of empirical data collected on the demographics of owned dogs in Villa de
Tezontepec and data available from the peer-reviewed literature. Model outcomes were assessed
using a 20-year time horizon. The model was used to examine: 1) the effect of surgical
sterilization strategies focused on dogs of any age (including a mixture of young dogs (i.e., not
yet reached sexual maturity), and dogs that have reached sexual maturity), 2), the effect of
surgical sterilization interventions focused only on young dogs, 3) the effect of increased dog
confinement, and 4) the bundled effect of concurrent surgical sterilization and increased dog
confinement. Model outcomes suggested that as surgical capacity increases from 21 to 84
surgeries/month (for dogs of any age), the mean dog population size after 20 years was reduced
101
by 14.1% and 78.7%, respectively compared to the base case scenario (in the absence of
intervention). Model outputs suggested that surgical sterilization interventions focused only on
young dogs yielded greater reductions (81.1% - 89.7%) in the mean population size than surgical
sterilization interventions focused on dogs of any age (14.1% - 78.7%, depending on the level of
surgical capacity). As the proportion of dogs that are confined increases from 50% to 90%, mean
dog population size after 20 years also decreases, but not considerably until confinement exceeds
70% (e.g. 33.6% reduction in population size if 80% of dogs are confined). Lastly, model results
suggested concurrent surgical sterilization and increased dog confinement interventions could
yield greater reductions in population size than surgical sterilization or dog confinement
interventions alone. In conclusion, our model suggested that sterilization of greater numbers of
young dogs and increased dog confinement could enhance the efficacy of existing surgical dog
population control interventions.
KEYWORDS: Agent-based, domestic dog, modeling, population control, population dynamics,
reproduction.
1. Introduction
Free-roaming dogs are a global problem that affects countries of all degrees of economic
development, but especially poorer countries (Villa et al., 2010). Every year around the world,
millions of dogs are euthanized after being abandoned by their owners because they are no
longer wanted or the owners are unable to care for them (Kass et al 2001; Davis et al, 2007;
Marsh 2010; Yen et al, 2014). Despite a large number of dogs being euthanized, people continue
to breed their dogs intentionally or accidentally (Fennell, 1999). When a population of dogs
102
grows uncontrollably, dog welfare, and the safety and health of people are affected (Downes et
al., 2009; World Organization for Animal Health (OIE), 2016; Salamanca et al, 2011).
Owned dogs (those for which someone claims some right over or states they are their
property (ICAM, 2008)) play an important role in sustaining the population of stray dogs (freeroaming, non-owned dogs) (Jackman and Rowan, 2007), when they or their offspring are
abandoned to the streets. This dynamic moves these dogs from “owned” to dogs that no longer
have direct care from humans and therefore become non-owned and free-roaming. Once these
dogs are on the streets they contribute to dog overpopulation if they are not sterilized or removed
from the population, as they will be able to reproduce freely.
Surgical sterilization is the most commonly performed pet contraception procedure in
veterinary practice (Howe, 2006). Sterilization can help control dog overpopulation, as well as
prevent some canine diseases such as mammary neoplasia or benign prostatic hyperplasia
(Schneider et al., 1969; Brendler et al., 1983; Howe, 2006). While surgical sterilization is
commonly used in developed countries, the high cost and limited resources (including veterinary
surgeons) in many developing countries makes surgical sterilization an infeasible method of
population control for large-scale application (Jana and Samanta, 2007). Evidence from a single
study has suggested that the stabilization of a dog population can been achieved after 70% of
female dogs have been sterilized (Amaku et al., 2010); however, it is unlikely that developing
countries could achieve such a high level of surgical sterilization.
Many developing countries have limited funds and resources to address and control their
dog populations. For this reason, dog population control programs need to be carefully designed
to not only have high intervention effectiveness but also be good value for money. Mathematical
models and computer simulation can provide a methodological framework within which
103
intervention strategies can be simulated and evaluated without incurring the actual cost of
implementation. These types of models can also be used to evaluate the potential effectiveness of
different dog population control interventions. The use of simulation models can therefore help
to identify how to best target and optimize the limited resources that are available for dog
population control measures.
Villa de Tezontepec is one of the 84 municipalities in the state of Hidalgo, in centraleastern Mexico. The availability of detailed empirical data on the owned-dog population in this
community, made it an ideal case study for the development and evaluation of a dog population
model. The municipality has an estimated human population of 11,746, (National Institute of
Statistics and Geography (INEGI), 2010). Kisiel et al. (2016) reported that Villa de Tezontepec
had an estimated human: owned dog ratio of 3.4:1 and that more than half (65.2%) of the
households in the municipality owned one or more dogs. Approximately 74.4% of the owned
dogs were older than one year, and only 45% of the owned dogs were kept confined when
unsupervised. Surgical sterilization was more common in female dogs (36.9%), than male dogs
(14.1%). Out of all reported surgically altered dogs, 80.0% were sterilized during subsidized
government spay/neuter clinics. At the time of writing, the government surgical sterilization
program within this region used a “mixed” approach where both young dogs (sexually immature)
and adult dogs (sexually mature) are sterilized, with no specific preference for younger or adult
dogs.
Using a stochastic, agent-based model, informed by empirical data collected in Villa de
Tezontepec, Hidalgo Mexico (Kisiel et al., 2016), the objective of this study was to compare the
projected impact of surgical sterilization interventions (focusing on dogs of different ages and
with varying surgical capacity) and increased dog confinement on the total owned dog
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population size over a 20-year time period.
2. Materials and methods
2.1 Model description
A stochastic, agent-based model was constructed using Anylogic, University, 7.2.0 (XJ
Technologies). The model framework was based on the development of a synthetic population
(in silico) of owned male and female dogs in Villa de Tezontepec, Hidalgo. The synthetic
population of owned dogs included both individuals that were confined (not permitted to roamfreely), and individuals that were unconfined (allowed by their owner to roam-free and
unsupervised). The model was designed to evaluate the potential impact of implementing
different strategies for 1) surgical reproductive control (i.e., surgical resources allocated to dogs
of different ages, and at varied levels of surgical capacity), and 2) dog confinement (increased
confinement levels for owned dogs), on the total owned dog population size over a 20-year time
period.
2.2. Model Synthetic Population Structure
The individual agents in the model represented female and male owned dogs. “Owned”
dogs were defined as those dogs for which someone claims some right over or states that they are
their property (ICAM, 2008). The initial synthetic population of dogs consisted of 2924 owned
dogs, based on observed dog ownership data from the region (Kisiel et al., 2016), specifically
related to the number of households owning dogs, and the number of dogs owned per household.
This dog population size of 2924 dogs (Kisiel et al., 2016) was used to establish an upper limit of
community capacity for owned dogs; this community capacity value was included in the model
to limit the exponential growth of the owned dog population. Once the community capacity
value was reached in the model, any owned dogs that were added to the population (e.g. new
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births) were immediately transitioned to the final death state, until the population size of owned
dogs decreased below the community capacity. The model population of owned dogs was
assumed to be open with births and deaths, immigration and emigration (further described
below). Individual owned male and female dogs were characterized by defined life cycle states
(stages) described in Figure 1 (males) and Figure 2 (females). The model considered aging
between life cycle states. The model was run for a period of 20 years, with one time-step
representing one year.
2.3. Model Parameterization
The model was parameterized using a combination of empirical data for Villa de
Tezontepec, Hidalgo, Mexico (Kisiel et al., 2016), wherever possible, and data available from
the peer-reviewed literature. Both age-related and non-age related (e.g. traffic accidents, disease)
mortality was considered in the model (Table 1). Non-age related risk of mortality did not differ
between males and females, but did differ between confined and unconfined owned dogs. Agerelated mortality was different for males and females (based on empirical data for Villa de
Tezontepec, Hidalgo, Mexico) (Table 1). Model parameters included both static, fixed parameter
values, and parameter distributions for model parameters for which there was sufficient
empirical data from Villa de Tezontepec, Hidalgo, Mexico (Table 1). A complete description of
all model parameters is provided in Table 1. Initial model conditions are described in Table 2,
and were based on empirical data (Kisiel et al., 2016). For this model, we used the reported
proportion of owned dogs kept confined (45%) in Villa de Tezontepec (Kisiel et al., 2016), as
per Table 2. The parameter describing the time to sexual maturity (representing the time that it
takes for a female dog to reach sexual maturity) (Table 1) was described by a uniform
distribution. A uniform distribution was selected to represent the range of values described in the
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peer-review literature for this reproductive process (Kustritz, 2010). We assumed that owned
female dogs had an equal chance to become reproductively active within the specified range used
for the time to sexual maturity for female dogs. Age related mortality parameters (representing
the risk of mortality due to old age) were described by an exponential distribution (Table 1). An
exponential distribution was selected for these mortality parameters because it was assumed that
dogs over a year old die continuously and independently at a constant average rate.
2.4. Model parameter assumptions
In the synthetic population, all owned female dogs were assumed to be equally fertile and
the risk of pregnancy was different for confined and unconfined female dogs. Unconfined owned
female dogs were assumed to have a higher risk of pregnancy as described by the empirical data
for Villa de Tezontepec, Hidalgo, Mexico (Kisiel et al., unpublished data) (Table 1). Unconfined
owned dogs were assumed to have a higher risk of mortality (Fielding, 2010). For this model, we
assumed that the risk of mortality for unconfined owned dogs was double the value of the risk of
mortality of owned confined dogs (Table 1). It has been reported that sterilization increases a
dog’s life expectancy (Hoffman et al., 2013). Therefore, we assumed that both non-age related
mortality, and age-related mortality were different for owned dogs that were sterilized compared
to those that were not (Table 1). For this model, it was assumed that sterilization increased
annual survival by 10%.
2.5. Immigration and Emigration
Immigration and emigration events occurred four times a year (i.e. every 0.25 years). At
each immigration event, both female and male owned dogs were randomly added to the
population at the “Puppy” state. Empirical data for Villa de Tezontepec, Hidalgo, Mexico (Kisiel
et al., unpublished data) indicated that the majority of the owned dogs that immigrate to the area,
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do so as puppies. As such, each of the dogs added to the population as part of an immigration
event were intact and non-reproductive. At each emigration event, a proportion of female and
male dogs were randomly removed from the population across all age groups and reproductive
statuses.
2.6 Model life cycle states
2.6.1. Male Dogs
Owned male dogs followed the life cycle states described in Figure 1. This cycle included
age-specific states labeled Puppy (aged birth to 8 weeks), Young (aged 8 weeks to 8 months),
and Adult (8 months and older). The choices for differentiation between age-specific states
relate to modeling the impacts of population control interventions, rather than biological age. All
states were mutually exclusive of one another. Within the Adult state, a Reproductive sub-state
was also included, to identify male dogs that had reached sexual maturity. An independent
Neutered state was included to designate male dogs that had been surgically sterilized (Figure 1).
Transitions (arrows) governing the movement of male dogs from one state to another (Figure 1)
are described in Table 1.
2.6.2. Female Dogs
The life cycle of owned female dogs in the model is described by Figure 2. Owned
female dogs could be in one of three mutually exclusive age-based states that included Puppy
(aged birth to 8 weeks), Young (aged 8 weeks to 4 - 8 months), and Adult (4 - 8 months and
older). The Adult state included three mutually exclusive sub-states to describe the female
reproductive cycle: In Heat (Reproductive), Pregnant, and Not in Heat. An independent Spayed
state was also included in the model to designate female dogs that had been surgically sterilized
(Figure 2). Transitions (arrows) governing the movement of female dogs from one state to
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another (Figure 2) are described in Table 1.
When owned female dogs became adults in the model, they transitioned immediately to
the In Heat state (representing their first heat event). Dogs in the In Heat state were considered
fertile and available for possible mating and subsequent pregnancy. From the In Heat state,
female dogs either transitioned back to the Not In Heat state or transitioned to the Pregnant state
based on the pregnancy parameters (Table 1). From the Pregnant state, female dogs moved back
into the Not In Heat state, based on the gestation period (Kutzler, 2010) (Table 1). At the end of
each gestation period, a litter of four new puppies (two male and two female, based on empirical
data for the region (Kisiel et al., 2016)) (Table 1), was added to the owned dog population in the
Puppy state. We assumed that female dogs were only eligible for surgical sterilization if they
were between heats. Although government subsidized spay and neuter programs in the
municipality of Villa de Tezontepec might sterilize female dogs in heat or in the early stages of
pregnancy, it has been stated that this is a rare occurrence (Health Services in the State of
Hidalgo (SSEH), 2016, personal communication), and therefore, we simplified the assumption to
only consider females between heats as eligible for the surgical intervention.
2.7. Model output
Each model simulation scenario used a 20-year time horizon and was run for 1000
iterations to capture variability between model realizations. The primary outcome of interest was
the final owned dog population size after 20 years. Owned dog population size was defined as
the total number of dogs (both male and female) at the end of the simulated 20-year period. The
primary outcome of interest (final population size) was aggregated across 1000 model iterations
by calculating the mean and median population size, standard deviation, and absolute range
(minimum to maximum) for each intervention scenario. The median owned dog population size
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was used to graph the simulation results, as well as the 25th and 75th percentiles and the
maximum and minimum adjacent values, defined as the highest and lowest values within 1.5 of
the inter quartile range (distance between the 25th and 75th percentiles of the data) above and
below the upper and lower quartiles respectively (Cox, 2009), excluding outliers. Outliers were
represented individually. An outlier was defined as an observation point that was above or below
the maximum and minimum adjacent values. Each set of model outcomes (1000 replicates per
intervention) were compared to the base case scenario (i.e. a simulation using the initial model
parameter values but in the absence of any interventions), and to each other for each type of
intervention (Table 3). Model outputs were visualized and analyzed using the statistical software
package STATA/SE for Mac (StataCorp LP, 2015).
2.8. Base case scenario
The model base case scenario used the initial conditions (Table 2), and model parameter
values (Table 1) described, but in the absence of any interventions.
2.9. Population Control Interventions
Surgical sterilization, dog confinement, and a combination of surgical sterilization and
dog confinement interventions (Table 3) were simulated using our base case model. All surgical
sterilization interventions took into consideration the reported proportion of owned dogs kept
confined (45%) in Villa de Tezontepec (Kisiel et al., 2016), as per Table 2.
2.9.1. Surgical Sterilization Interventions
Surgical sterilization of dogs was considered permanent for the life of the dogs. We
examined two different surgical sterilization intervention strategies. These strategies varied in
that they targeted dogs of different ages and also modeled different levels of surgical capacity
(number of surgeries performed per unit time). The government in this region currently uses a
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“mixed” approach (sterilization of both young, sexually immature dogs and adult dogs) and
therefore, this is one of the strategies considered in our model. We modeled a mixed age
surgical sterilization intervention scenario at three different levels of surgical capacity. Capacity
level 1 is based on the number of monthly surgeries (21) currently performed by the Ministry of
Health in the State of Hidalgo in Villa de Tezontepec (SSEH, personal communication, 2016);
on average, this includes 6 adult males, 13 adult females, 1 young male, and 1 young female dog.
For comparison, we also modeled increased surgical capacity at 42 surgeries per month and at 84
surgeries per month (using the same sex distribution as the lowest surgical capacity (21 surgeries
per month) described above)) (Table 3).
There is evidence that suggests that targeting surgical sterilization to young female dogs
(before they reach sexual maturity) improves dog population control interventions (Di Nardo et
al., 2007). Therefore, we also examined the potential impact of focusing surgical sterilization
interventions on young, sexually immature dogs (both female and male), using the same sex
distribution as for the current government surgical sterilization program (Secretaria de Salud,
2015). For these young age surgical sterilization intervention scenarios, we examined the same
three levels of surgical capacity as for the mixed age surgical sterilization interventions (21, 42,
and 84 surgeries per month).
2.9.2. Dog Confinement Intervention
Empirical data collected from Villa de Tezontepec, Hidalgo, Mexico indicates that only
45% of owned dogs were kept confined when unsupervised; the rest (55%) of the owned dog
population was unconfined and allowed to roam-freely within the community (Kisiel et al.,
2016). Unconfined, owned free-roaming dogs that are not sterilized could contribute to the
growth of the dog population. We used our model to examine an intervention aimed at
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encouraging dog owners to confine their dogs rather than allowing them to roam. We assumed
that educational campaigns could result in an increase in the proportion of dogs confined (not
allowed to roam-free when unsupervised). For this model intervention, we varied the proportion
of dogs confined from 50% (representing an educational intervention that led to half of the dog
owners confining their dogs when unsupervised) to 90% (representing an educational
intervention that resulted in 90% of owners confining their dogs). The proportion of owned dogs
confined was varied in increments of 10% (Table 3).
2.9.3. Combined Surgical Sterilization (mixed age group) and Dog Confinement
Intervention
In this intervention scenario, we examined the effect of surgical sterilization (mixed age
group) combined with different levels of dog confinement (Table 3).
2.10. Sensitivity analyses
We conducted sensitivity analyses to evaluate the potential impact of our model
specification and parameter uncertainty. The parameter values describing the risk of pregnancy
for owned female dogs, as well as the parameter values describing the annual risk of non-age
related mortality for owned dogs of different ages and for confined versus unconfined owned
dogs, were identified as being of specific concern as they were based on assumptions (as
empirical data from the region were not available for unconfined owned dogs). In order to
identify biologically realistic ranges for the sensitivity analyses around the empirical estimates, a
literature search for dog demographic studies conducted in Latin America (that reported values
for the parameter values of interest) was conducted. The maximum values of the ranges used in
the sensitivity analyses (for the mortality parameters), were estimated by calculating the mean
value from all the parameters found in the peer-review literature (Morales and Ibarra 1979;
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Ibarra et al 1991; Morales et al., 1992; Ibarra et al 1997), for each of the parameter values of
interest. These calculated mean values were used as the maximum values of the ranges, because
the empirical values from Vila de Tezontepec were lower than the calculated mean values. The
minimum values of the ranges used in the sensitivity analyses, were assumed to be half of the
empirical values from Villa de Tezontepec. Since there were no data available from the peerreviewed literature (in Latin America) for the risk of pregnancy values, the lower and upper
range values for this parameter were assumed to be plus 15% and minus 14% of the empirical
risk of pregnancy from Villa de Tezontepec. For the range of values determined as biologically
reasonable (Table 1) for our model sensitivity analysis, all model intervention scenarios were
varied independently and re-run (1000 iterations each). Model outputs were compared to identify
if changing the model inputs resulted in numerically different model outputs in terms of average
projected population size after 20 years.
We present the results of our sensitivity analysis for the mixed age and young age sterilization
interventions in Appendix B. Model outputs across the range of parameter values examined were
compared and graphed using the statistical software package STATA/SE for Mac (StataCorp LP,
2015).
3. Results
3.1. Base case simulations
The base case model resulted in an owned dog population with a mean population size of
2934 (SD = 6.2; median: 2936, range: 2878 to 2945) over 1000 simulation iterations (Table 4),
with the maximum owned dog population size constrained by the pre-defined community
capacity of the population.
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3.2. Mixed Age Surgical Sterilization Intervention
Using a mixed age surgical sterilization intervention, as surgical capacity increased, the
median owned dog population size decreased over the 20-year time period (Table 5, Figure 3).
Mixed age surgical sterilization interventions at the lowest surgical capacity (21 surgeries),
resulted in a 14.1% reduction in the mean owned dog population size compared to the base case
scenario with no sterilization interventions (Table 5). An intervention scenario with increased
surgical capacity (42 surgeries) had a more pronounced reduction in the owned dog population
size (Figure 3). In this case, the mean owned dog population size was 1564 dogs (SD = 341.1)
(Table 4), representing a 46.7% reduction in the final mean owned dog population size compared
to the base case scenario (Table 5). At the highest surgical capacity (84 surgeries per month), a
mean reduction of 78.7% was observed (Table 5).
3.3. Young Age Surgical Sterilization Intervention
A surgical intervention that used the same range of surgical capacities (21, 42 and 84
surgeries per month) but focused the surgical capacity on young, sexually immature dogs
resulted in model outcomes where the owned dog mean population size was markedly reduced,
compared to the base case scenario and the reductions projected for the mixed age surgical
intervention (Table 5). For sterilization interventions that were focused on young sexually
immature dogs, as the surgical capacity increased, the median owned dog population size also
decreased (Figure 3). For example, the young age surgical sterilization intervention at the lowest
surgical capacity, resulted in a mean owned dog population size that had 415 fewer dogs after 20
years compared to the base case scenario, which represented a mean owned dog population size
reduction of 81.0% compared to the base case scenario (Table 5). Furthermore, when young age
surgical sterilization interventions were compared to the mixed age surgical sterilization
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interventions with the same level of surgical capacity, the projected owned dog population size
percent reduction across the three levels of surgical capacity (21, 42 and 84 surgeries per month)
were -78.0%, -78.0% and -51.0% (Table 6). Hence, the difference in mean owned dog
population size between mixed age surgical sterilization and young age surgical sterilization
interventions, both at the lowest level of surgical capacity, resulted in a 78% greater reduction
with young age sterilization (Table 6). In general, across all levels of surgical capacity, mean
population size reductions were greater for surgical interventions focused on young dogs rather
than dogs of mixed ages (Figure 3).
3.4. Dog Confinement Intervention
Increasing the proportion of confined dogs from 50 – 70% did not result in a considerable
reduction in the mean owned dog population size over the 20-year horizon (Table 7); however,
once the proportion of confined dogs exceeded 70%, there was a more substantial reduction in
mean owned dog population size (Figure 4). For model simulations that assumed that 80% of
dogs were confined, the projected mean owned dog population size was 1949 dogs (SD = 258.5)
(Table 4). This amounts to a reduction in the projected mean owned dog population size of
33.6% compared to the base case scenario over the 20-year horizon (Table 7). Further gains were
achieved by increasing the proportion of confined dogs to 90% (mean=1078; SD = 113.0) (Table
4), which resulted in a reduction in the mean dog population size of 66.3% compared to the base
case scenario (Table 7).
3.5. Combined Mixed Age Surgical Sterilization (21 surgeries/month) And Dog
Confinement
When we evaluated the combination of the mixed age surgical sterilization with
improved dog confinement, the model projected a synergistic effect with a substantial decrease
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in the owned dog population size (Figure 4). Mixed age surgical sterilization at the lowest
surgical capacity level (21 surgeries per month) combined with 50% of owned dogs being
confined resulted in a mean population size of 2404 dogs (SD = 553.8), representing a mean
owned dog population size reduction of 18.1% compared to the base case scenario (Table 7). In
contrast, when we compared 50% dog confinement alone (Table 3) against the base case
scenario, we found there was no reduction (0%) in the projected owned dog population size
(Table 7). When we compared the combined intervention (Table 3), to the single mixed age
surgical sterilization at the lowest surgical capacity level (Table 3) without the increased dog
confinement, we found only a 4.6% reduction in the projected owned dog population size (Table
8). Hence, the greatest reductions in owned dog population size were observed with the
combined used of mixed age sterilization of dogs and increasing levels of dog confinement.
3.6. Sensitivity analyses
Varying the annual risk of mortality for puppies in the model (from 5% to 30%) resulted
in only a small mean population size difference and did not change the relative impact of the
different interventions under consideration for both the young and mixed age sterilization
interventions (Appendix B.1, Appendix B.5). Examining the projected effects of a similar
magnitude of change to the annual risk of mortality for young dogs demonstrated that in general,
the model was also robust to a range of assumptions about this parameter value (Appendix B.2,
Appendix B.6). However, when the annual risk of mortality for young dogs was reduced to 10%
(the lowest level examined), the attractiveness of the middle surgical capacity (42 surgeries per
month) was reduced for the mixed age sterilization intervention (Appendix B.2). Varying the
parameter values for the annual risk of mortality for adult dogs from 1.5 – 7.5% did not impact
the relative effectiveness of either the young or mixed age sterilization interventions (Appendix
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B.3, Appendix B.7). A substantial reduction in the risk of pregnancy parameter (from 26% to
10%) resulted in outcomes that made the surgical sterilization interventions examined more
attractive and less variable compared to the baseline parameter value for pregnancy (Appendix
B.4, Appendix B.8). Altering the risk of mortality and pregnancy within reasonable biological
ranges was not found to result in a considerable difference in the expected impact of the model
interventions under study. As such, the model was deemed robust to a range of input parameter
values.
4. Discussion
The control of dog reproduction is one of several measures that can be used to control the
size of dog populations (OIE, 2016). Surgical sterilization is the most commonly used method of
pet contraception (Howe 2006). Several mathematical models have been developed to evaluate
the effect of sterilization programs on dog population size in Italy (Di Nardo et al., 2007), Brazil
(Amaku et al., 2009; Amaku et al., 2010; Baquero et al., 2016), and India (Totton et al., 2010;
Yoak et al, 2016). However, these models did not specifically consider the individual population
characteristics (e.g. age structure and confinement) of owned dog populations, and how such
characteristics can impact the effectiveness of population control interventions. Currently, the
government sterilization program in Villa de Tezontepec has a maximum surgical capacity of 21
surgeries per month (roughly 8.5% annual sterilization) and focuses on dogs of mixed ages. Our
model suggests that long-term deployment of the mixed age surgical sterilization intervention at
the lowest surgical capacity examined (in line with the existing program) combined with the
current proportion of owned dogs that are confined (45%), could only reduce the mean dog
population by 14.4% after 20 years. We used our model to examine the impact of changing the
existing surgical capacity, the ages of the dogs receiving the intervention, and/or the impact of
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dog confinement. Our findings suggest that if the number of sterilizations were to double (42
surgeries/month: roughly 18.7% annual sterilization), the owned dog population could decrease
by 46.7% in the same 20-year time period. This finding is compatible with results reported by
Amaku et al. (2010), which showed that a population reduction of 50% could be achieved in less
than 10 years if the probability of sterilization was higher than 20%. However, the time frame at
which population reduction is achieved in our model is longer (20 years) compared to the one
reported by Amaku et al. (2010). Our results suggest that the current government spay and neuter
program in this community does impact the owned dog population as a whole; however, the
reduction might be relatively small over the long term. The current model suggests that doubling
or quadrupling the number of mixed age sterilizations per month could result in a much larger
reduction in the owned dog population size over a 20-year period. However, such surgical
increases may be difficult to sustain over the long term for a single region, due to the costs and
required program resources.
Previous studies have suggested that dog population control programs should focus on
the spaying of young female dogs (i.e. before they have a first litter) in order to be cost-effective
(Di Nardo et al., 2007). Our results suggest that sterilization efforts focused on both female and
male young dogs (i.e. before sexual maturity), could enhance the efficacy of the current surgical
owned dog population control program for this community without the need to increase the
current surgical capacity. Re-allocating the existing resources to younger owned dogs could
reduce the owned dog population size more markedly over the same 20-year time period,
assuming that cost and the probability of dog owner participation in the intervention are the same
as for the current intervention. We did not model preferential spaying of young females, because
the current government program includes the sterilization both females and male dogs; however,
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evaluating the effect of preferential spaying of young females could be considered in the future.
Non-surgical intervention measures can also be used to control the size of the owned dog
population. The implementation of an educational program to create awareness about adequate
dog confinement is one example (OIE, 2016). Confinement of owned dogs is not only useful for
controlling population growth, but is also beneficial for the health and safety of the public and
other dogs, as it can result in reduced bites and/or aggressive incidents between people and dogs.
To the authors’ knowledge, no models have evaluated the potential impact of dog confinement
on the owned dog population size. Our model suggests that increasing the proportion of owned
dogs confined (e.g. via the implementation of educational programs) could help reduce the
owned dog population size over time. However, achieving such a high proportion of confinement
is likely not possible, and secondary impacts related to this management strategy, such as the
animal welfare implications of dog confinement, would need to be evaluated further.
We also used the model to test a bundled intervention; specifically, the effect of mixed
age surgical sterilization at the existing surgical capacity level (21 surgeries per month) in
combination with a reduction in the proportion of unconfined owned dogs. These results suggest
that if the local government were to continue their current sterilization program and add an
intervention to increase the proportion of owned dogs that are currently confined (45%), the
owned dog population could be reduced further without investing in additional surgical capacity.
However, increasing the number of confined owned dogs to the levels required to make a
meaningful impact may be difficult to accomplish. The success of such an intervention would
depend on several socio-economic and cultural conditions. There are no current studies regarding
the cost-effectiveness of interventions related to dog confinement or the likelihood of community
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uptake with such an intervention. Therefore, further studies would be necessary to evaluate the
feasibility of this approach.
Model sensitivity analyses were performed to evaluate the possible impact of changing
assumptions regarding the model parameters for pregnancy and mortality. Changes to the risk of
mortality (within reasonable limits based on the literature) increased the variability of results
around the low surgical capacity intervention, but did not change the variability in model
outcomes observed for the higher surgical capacity interventions or their attractiveness in terms
of relative benefit. Collecting and using accurate dog population numbers and attributes,
including risk of mortality and pregnancy estimates, are very important (Di Nardo et al., 2007),
especially when models are used to evaluate population control interventions. Due to a lack of
data related to the risk of mortality and pregnancy for unconfined owned dogs, we made the
assumption that the risk of pregnancy and mortality for unconfined owned dogs was double that
of confined owned dogs. This could have impacted our model results in several ways. An
increase in the risk of pregnancy could make the lower and middle surgical capacity
interventions seem less attractive; however, our sensitivity analysis demonstrated that an increase
in the risk of pregnancy from the current model values had a relatively small effect on the model
outcomes for the lower and middle surgical capacity interventions. If the annual dog mortality in
our model was higher than the real-life conditions our findings would be conservative estimates
of the overall intervention effect size. Our sensitivity analysis also indicated that an increase in
the risk of mortality in young and adult dogs had a greater effect on the model outcomes than an
increase in the risk of mortality in puppies. This is especially true in the low surgical capacity
intervention. However, the effect became much smaller in the middle and high surgical capacity
interventions. Our sensitivity analyses examined model outcomes across a range of pregnancy
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values and highlighted that surgical sterilization interventions, even at the lowest surgical
capacity (21 surgeries per month), become more attractive as the baseline risk of pregnancy is
reduced. This result suggests that by reducing the interest and/or willingness of owners to breed
their pets, the interventions examined here are expected to have an even greater impact. In
general, despite uncertainty around the baseline risk of pregnancy and non-age related mortality
parameters, we have shown that the model is relatively robust to these assumptions and the
projected impact of our modeled interventions do not change considerably if we vary these
parameters across a range of realistic values.
5. Limitations
All models are simplifications of reality and therefore, as with any model-based analysis,
ours has limitations. This model only considered the owned dog population in this region and
did not consider stray (non-owned, free-roaming dogs) or feral (dogs living in a “wild and free
state” without intentional or direct food or shelter provided by people) dog populations (Boitani
et al. 2007). Therefore, this model only describes a part of a larger population model.
Consequently, the results of these model simulations do not reflect the total impact of the
interventions on the overall dog population size for this community. However, surgical
sterilization interventions in this region are exclusively targeted at owned dogs. For this reason,
we believe it was appropriate to model only the owned dog population to evaluate the effect of
surgical sterilization interventions. This model did not consider the growth of the human
population in the 20-year period, which could influence the community capacity used for this
model. The model assumed all owned dogs that immigrate to the population were newborn
puppies and not sterilized. Although empirical data from this region suggests that this is a
reasonable assumption, this may have influenced the interventions being studied. For our model,
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we also assumed that sterilized owned dogs live longer (had a 10% increase in life expectancy)
than non-sterilized owned dogs. This assumption was based on findings reported by Hoffman et
al. (2013), which indicated that sterilization increases life expectancy by 13.8% in males and
26.3% in female dogs. These reported results are based on data from North American veterinary
teaching hospitals in the United States, which might not reflect the health condition of animals in
Villa de Tezontepec. As a result, we constrained our assumption to a conservative 10% increase
in life expectancy for sterilized owned dogs. Lastly, all females in the model were considered to
be fertile, but in reality, this might not be the case. Our assumption therefore provided a worstcase scenario in terms of possible population growth. Violating this assumption would increase
the attractiveness of our modeled interventions and predict even lower population sizes of owned
dogs in Villa de Tezontepec. One of the implications of capping the owned dog population size
in the model (establishing a community capacity) was not being able to detect the growth of the
owned dog population over time beyond the community capacity, both in the absence and
presence of dog population control interventions (i.e. surgical sterilization and dog confinement
control). Therefore, our model was not able to capture the potential growth of the owned dog
population in the long term beyond the community capacity.
6. Conclusion
Our model findings suggest that the sterilization of young, sexually immature dogs could
be more successful at reducing the owned dog population size than sterilization focused on dogs
of any age over a 20-year time horizon. Confinement of dogs alone could have the ability to
affect the owned dog population size considerably when the proportion of confined dogs is more
than 70%; however, achieving such a high proportion of confinement is likely not possible.
Reducing the proportion of owned female dogs becoming pregnant also had an effect of
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decreasing the population size, suggesting that if owners were discouraged from breeding their
female dogs, this alone could reduce the owned dog population size. Computer simulation
models can help governments and other decision-makers to explore options for optimizing the
limited resources allocated for dog population management programs. Our model could be
expanded to incorporate the free-roaming, non-owned dog population to evaluate population
control methods for the total dog population in this location. This model could also be expanded
to evaluate the effect of non-surgical dog sterilization programs (e.g. chemical sterilization), as
well as targeting only female dogs for sterilization. These additional strategies are especially
important when considering the potential impact of dog reproduction control interventions for
free-roaming dog populations.
6. Conflict of interest statement
The authors declare that they have no conflicts of interest.
7. Acknowledgements
The authors thank the Health Services of the State of Hidalgo for providing information
regarding their subsidized spay and neuter program in Villa de Tezontepec, Hidalgo, Mexico.
The authors gratefully acknowledge the Canada Research Chairs Program (ALG) for funding.
The study sponsor had no involvement in the study design, the collection, analysis and
interpretation of data, the writing of the manuscript, or the decision to submit the manuscript for
publication.
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128
Table 1. Model parameters describing the transition rates and/or times for individual dogs to move between the different model states.
Puppy annual risk of mortality
unconfined
Puppy annual risk of mortality
confined
Time to sexual maturity male
Time to sexual maturity female
Time to weaning
0.20 per year (Sensitivity
analysis range from 0.1 to 0.3)
0.20 per year
0.10 per year (Sensitivity
analysis range from 0.05 to
0.3)
Average 10 months
Average 6 to 10 months
8 weeks
N/A
N/A
N/A
N/A
N/A
Uniform (Min. 6 months Max. 10 months)
N/A
Kisiel et al., unpublished data (Sensitivity analysis:
Morales and Ibarra 1979; Ibarra et al., 1991;
Morales et al., 1992; Ibarra et al., 1997)
Assumption (2 X Young annual risk of mortality
confined)
Kisiel et al., unpublished data (Sensitivity analysis:
Morales and Ibarra 1979; Ibarra et al., 1991;
Morales et al., 1992; Ibarra et al., 1997)
Assumption (2 X Puppy annual risk of mortality
confined)
Kisiel et al., unpublished data (Sensitivity analysis:
Morales and Ibarra 1979; Ibarra et al., 1991;
Morales et al., 1992; Ibarra et al., 1997)
Kustritz, 2010
Kustritz, 2010
Kustritz, 2010
Reference
Young annual risk of mortality
confined
0.40 per year
N/A
Assumption (2 X Adult annual risk of mortality
confined)
Distribution (distribution parameters)
Young annual risk of mortality
unconfined
0.03 per year (Sensitivity
analysis range from 0.015 to
0.075)
N/A
Assumption (90% of Adult annual risk of mortality
confined)
Value
Single fixed values were indicated by “N/A” in the distribution column.
Parameter
Adult annual risk of mortality
confined
0.06 per year
N/A
General parameters
Adult annual risk of mortality
unconfined
0.027 per year
Kisiel et al., unpublished data
Sterilized risk of mortality confined
Exponential (Min. 0.08 years, Max. 14
years, Skewness 2.3 and Kurtosis 10.2)
Kisiel et al., unpublished data
Assumption (2 X Sterilized risk of mortality
confined)
Male age related mortality
Exponential (Min. 0.5 years, Max. 12 years,
Skewness 1.5 and Kurtosis 5.1)
Assumption (90% of Male age related mortality)
N/A
Female age related mortality
Exponential (Min. 0.88 years, Max. 15.4
years, Skewness 2.3 and Kurtosis 10.2)
Assumption (90% Female age related mortality)
0.054 per year
Sterilized male age related mortality
Exponential (Min. 0.55 years, Max. 13.2
years, Skewness 2.3 and Kurtosis 10.2)
Sterilized risk of mortality
unconfined
Sterilized female age related
mortality
129
Risk of pregnancy unconfined
Risk of pregnancy confined
Litter size
Time to New proestrus
Gestation duration
Duration of heat
0.04 per year
0.23 per year
0.52 per year
0.26 per year (Sensitivity
analysis range from 0.10 to
0.40)
4 puppies
Average 7 months
65 days
18 days (Proestrus Average 9
days + Estrus Average 9
days)
Value
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Distribution (distribution parameters)
Kisiel et al., 2016
Kisiel et al., unpublished data
Kisiel et al., unpublished data
Assumption (2 X risk of pregnancy confined)
Kisiel et al., 2016 (Sensitivity analysis: based on
researchers hypothesis)
Kisiel et al., 2016
Kustritz, 2010
Kutzler, 2010
Kustritz, 2010, Kustritz, 2012
Reference
Table 1, continued.
Annual probability of immigration
N/A
Parameter
Annual probability of emigration
2924 dogs
Population parameters
Female dog only parameters
Community capacity
130
Table 2. Initial conditions of the agent-based model evaluating owned dog population control
interventions in Villa de Tezontepec, Hidalgo Mexico.
Parameter
Values
Reference
45%
Kisiel et al., 2016
Population size
1222 dogs
Kisiel et al., 2016
Proportion puppy
4%
Kisiel et al., unpublished data
Proportion young
11%
Kisiel et al., unpublished data
Population parameters
Proportion of confined dogs
Female dogs
Proportion in heat
Kisiel et al., unpublished data
(reproductive)
21%
Proportion pregnant
6%
Kisiel et al., unpublished data
Proportion not in heat
21%
Kisiel et al., unpublished data
Proportion regular spayed
37%
Kisiel et al., 2016
Population size
1702 dogs
Kisiel et al., 2016
Proportion puppy
6%
Kisiel et al., unpublished data
Proportion young
16%
Kisiel et al., unpublished data
Proportion reproductive
64%
Kisiel et al., unpublished data
Proportion regular neutered
14%
Kisiel et al., 2016
Male dogs
131
Table 3. Surgical and confinement interventions examined using the agent-based model
evaluating owned dog population control interventions in Villa de Tezontepec, Hidalgo Mexico.
Surgical sterilization
Intervention
A. Mixed age surgical sterilization
B. Young age surgical sterilization
(prior to sexual maturity)
Intervention
number
Surgical capacity
A.1
Level 1 - 21 surgeries per month
A.2
Level 2 - 42 surgeries per month
A.3
Level 3 - 84 surgeries per month
B.1
Level 1 - 21 surgeries per month
B.2
Level 2 - 42 surgeries per month
B.3
Level 3 - 84 surgeries per month
Intervention
number
Dog confinement proportion
C.1
50% Dog confinement
C.2
60% Dog confinement
C.3
70% Dog confinement
C.4
80% Dog confinement
C.5
90% Dog confinement
Dog confinement
Intervention
C. Dog confinement
Mixed age surgical sterilization & dog confinement
Intervention
D. Combined mixed age surgical
sterilization (level 1) and dog
confinement
Intervention
number
Dog confinement proportion
D.1
50% Dog confinement
D.2
60% Dog confinement
D.3
70% Dog confinement
D.4
80% Dog confinement
D.5
90% Dog confinement
132
Table 4. Model simulation results. For each intervention, the model was run 1000 times with the outcome of interest being the total
population size after 20 years. Outcomes are aggregated across all model iterations and summarized as mean population size, standard
D.3
D.2
D.1
C.5
C.4
C.3
C.2
C.1
B.3
B.2
B.1
A.3
A.2
A.1
N/A
Intervention
number
1009
1378
1996
2404
1078
1949
2864
2930
2933
303
339
558
624
1564
2519
2934
Mean population
size
52.5
101.1
278.6
594.2
553.8
113.0
258.5
118.3
12.2
8.3
23.7
29.8
122.1
91.1
341.1
496.7
6.2
Standard deviation
782
997
1314
1804
2672
1072
1919
2916
2935
2936
302
337
532
612
1525
2881
2936
Median population
size
648 - 958
750 - 1407
895 - 2723
1118 - 2936
1281 - 2938
748 - 1393
1387 - 2807
2279 - 2941
2836 - 2942
2870 - 2942
230 - 402
261 - 437
331 - 1125
418 - 983
798 - 2705
1443 - 2937
2878 - 2945
Range (min – max)
deviation, median population size and range.
Intervention
Base case
Surgical sterilization
A. Mixed age surgical
sterilization
B. Young age surgical
sterilization
Dog confinement
C. Dog confinement
D.4
785
D. Combined mixed age
surgical sterilization (level 1)
and dog confinement
Mixed age sterilization & dog confinement
D.5
133
Table 5. Difference in mean population size between the base case scenario and across all
intervention scenarios of the same type, for the mixed age surgical sterilization interventions and
the young age surgical sterilization. Percentages in brackets are the % reduction in mean
population size between the two interventions.
A. Mixed age surgical sterilization
Intervention number
Base Case
A.1
A.1
A.2
A.3
415
1370
2310
(-14.1%)
(-46.7%)
(-78.7%)
955
1895
(-37.9%)
(-75.2%)
0
A.2
0
A.3
940
(-60.1%)
0
B. Young age surgical sterilization
Intervention Number
Base Case
B.1
B.1
B.2
B.3
2376
2595
2631
(-81.0%)
(-88.4%)
(-89.7%)
219
255
(-39.2%)
(-45.7%)
0
B.2
0
B.3
36
(-10.6%)
0
134
Table 6. Difference in mean population size between mixed age surgical sterilization and young
age surgical sterilization interventions within the same level of surgical capacity. Level 1
represents a surgical capacity of 21 surgeries per month, level 2 represents 42 surgeries per
month, and level 3 represents 84 surgeries per month. Percentages in brackets are the %
reduction in mean population size between the two interventions.
A. Mixed age surgical sterilization
Intervention
A.1
A.2
A.3
1961
1006
66
(-78%)
(-65%)
(-11%)
2180
1225
285
(-87%)
(-78%)
(-46%)
2216
1261
321
(-88%)
(-81%)
(-51%)
B.1
sterilization
B. Young age surgical
number
B.2
B.3
135
Table 7. Differences in mean population size between the base case scenario and across all
intervention scenarios and combinations of the same type, for the dog confinement intervention
and the combined mixed age surgical sterilization (capacity level 1) and dog confinement
intervention. Level 1 represents a surgical capacity of 21 surgeries per month. Percentages in
brackets are the % reduction in mean population size between the two interventions.
C. Dog Confinement
INTERVENTION
NUMBER
Base Case
C.1
C.2
C.1
(50%
confined)
1
(-0.0%)
0
C.2
(60%
confined)
4
(-0.1%)
3
(-0.1%)
0
C.3
C.3
(70%
confined)
70
(-2.4%)
69
(-2.4%)
66
(-2.3%)
0
C.4
C.4
(80%
confined)
985
(-33.6%)
984
(-33.5%)
981
(-33.5%)
915
(-31.9%)
0
C.5
Mixed age sterilization & Dog Confinement
D.1
D.2
INTERVENTION
(50%
(60%
NUMBER
confined)
confined)
530
938
Base Case
(-18.1%)
(-32.0%)
408
D.1
0
(-17.0%)
D.2
0
D.3
D.3
(70%
confined)
1556
(-53.0%)
1026
(-42.7%)
618
(-31.0%)
0
D.4
D.4
(80%
confined)
1925
(-65.6%)
1395
(-58.0%)
987
(-49.4%)
369
(-26.8%)
0
D.5
136
C.5
(90%
confined)
1856
(-66.3%)
1855
(-63.2%)
1852
(-63.2%)
1786
(-62.4%)
871
(-44.7%)
0
D.5
(90%
confined)
2149
(-73.2%)
1619
(-67.3%)
1211
(-60.7%)
593
(-43.0%)
224
(-22.2%)
0
Table 8. Difference in mean population size between combined intervention at surgical capacity level 1, mixed age surgical
sterilization (without dog confinement), and dog confinement. Level 1 represents a surgical capacity of 21 surgeries per month.
Intervention
number
115
(-4.6%)
A.1
529
(-18%)
C.1
(50%
confined)
937
(-32%)
C.2
(60%
confined)
1555
(-53%)
C.3
(70%
confined)
1924
(-66%)
C.4
(80%
confined)
2148
(-73%)
C.5
(90%
confined)
Dog confinement
D.1
-1326
(+123%)
-455
(+23%)
460
(-16%)
-918
(+85%)
-47
(+2%)
868
(-30%)
934
(-32%)
-300
(+28%)
571
(-30)
1486
(-52%)
1552
(-53%)
69
(-6%)
940
(-48%)
1855
(-65%)
1921
(-66%)
293
(-27%)
1164
(60%)
2079
(-73%)
2145
(-73%)
526
(-18%)
523
(-20.8%)
1510
(-59.9%)
1141
(-45.3%)
D.4
1734
(-68.8%)
D.3
D.2
A. Mixed age
surgical
sterilization
Percentages in brackets are the % reduction in mean population size between the two interventions.
D. Combined mixed
age surgical
sterilization
(capacity level 1)
and dog confinement
D.5
137
Neutered
Event
Neutered
Event
Sterilized
Annual
Risk of
Mortality
Confined
Neutered
Sterilized
Annual
Risk of
Mortality
Unconfined
Birth
Puppy
Time to Weaning
Young
Time to Sexual
Maturity Male
Adult
Reproductive
Male
Sterilized Male
Age Related Age Related
Mortality
Mortality
Death
Puppy Annual
Risk of
Mortality Confined
Young Annual
Risk of
Mortality Confined
Adult
Annual
Risk of
Mortality
Confined
Puppy Annual
Risk of
Mortality
Unconfined
Young Annual
Risk of
Mortality
Unconfined
Adult
Annual
Risk of
Mortality
Unconfined
Figure 1. State chart for male dogs describing the individual life states and transitions in the agent-based model evaluating owned dog
population control interventions in Villa de Tezontepec, Hidalgo Mexico.
138
Spay
Event
Spay
Event
Spayed
Sterilized Sterilized
Annual
Annual
Risk of
Risk of
Mortality
Mortality
Unconfined Confined
Birth
Puppy
Time to Weaning
Young
Time to Sexual
Maturity Female
Adult
In Heat
(Reproductive)
Duration Time to New
of Heat Proestrus
Not in Heat
Sterilized Female Female
Age Related Age Related
Mortality
Mortality
Death
Puppy Annual
Risk of
Mortality Confined
Young Annual
Risk of
Mortality Confined
Risk of
Pregnancy
Confined
Risk of
Pregnancy
Unconfined
Puppy Annual
Risk of
Mortality Unconfined
Young Annual
Risk of
Mortality Unconfined
Pregnant
Gestation
Period
Adult
Annual
Risk of
Mortality
Confined
Adult
Annual
Risk
of
Mortality
Unconfined
Figure 2. State chart for female dogs describing the individual life states and transitions in the agent-based model evaluating owned
dog population control interventions in Villa de Tezontepec, Hidalgo Mexico.
139
Figure 3. Impact of mixed age surgical sterilization and young age surgical sterilization interventions after 20 years. Each box
represents a summary of the model outcome (population size) across 1000 model replicates. The top and bottom of each box are the
25th and 75th percentiles, and the line inside the box is the median dog population size. The top whiskers are the minimum and
maximum values of population size, excluding outliers, which are represented in the figure by solid circles. The dashed line represents
100%
75%
50%
25%
0%
A.
21
42
B.
21
140
Number of Surgeries per Month
84
42
84
the population community capacity. Panel A: Mixed age sterilization, Panel B: young age sterilization.
% Reduction in Population Size
Figure 4. Impact of dog confinement alone (Panel A) and the combination intervention (21, mixed age sterilizations per month + dog
confinement: Panel B). Each box represents a summary of the model outcomes across 1000 model replicates. The top and bottom of
each box are the 25th and 75th percentiles, and the line inside the box is the median dog population size. The top whiskers are the
A.
50%
60%
70%
80%
90%
B.
50%
141
% Dog Confinement
60%
70%
80%
90%
minimum and maximum values of population size, excluding outliers, which are represented in the figure by solid circles. The dashed
100%
75%
50%
25%
0%
line represents the population community capacity.
% Reduction in Population Size
CHAPTER FOUR
Conclusions, study limitations and recommendations for future research
4. Thesis summary and key recommendations
4.1. Summary
The uncontrolled growth of a dog population can have negative implications for the
health and safety of people, as well as a negative impact on canine welfare (Downes et al., 2009;
World Organization for Animal Health (OIE), 2016; Salamanca et al., 2011).
Semi-urban
communities (i.e. areas with 10,000 to 15,000 residents) in Mexico (Instituto Nacional de
Administracion Publica (INAP), 2009) typically have uncontrolled, free-roaming dogs. These
communities often lack the infrastructure for the provision of public services (INAP, 2009),
including animal control services. It is important for semi-urban communities to develop
evidence-based dog population control initiatives that can yield effective results, within the
constraints of limited veterinary resources and animal control infrastructure.
Understanding the demography and ecology of a dog population can help inform the
planning, implementation, and monitoring of appropriate dog population management programs
(World Health Organization (WHO), 1987; WHO/World Society for the Protection of Animals
(WSPA), 1990; Perry, 1993; Patronek and Rowan, 1995; Acosta-Jamett et al., 2010; Morters et
al., 2014). Furthermore, dog abundance estimates can help project the costs and resources needed
for population control interventions (Wandeler, 1985). Data on dog population demographics can
also be used to inform the development of computer simulation models, which in turn, can be
used to help identify how to best target and optimize the limited resources that are available for
dog population control measures in developing countries. Few mathematical models have been
142
developed to describe the population dynamics of domestic dogs and to evaluate different
strategies to control their populations (e.g. culling, and/or sterilization) (Amaku et al., 2009;
Amaku et al., 2010; Baquero et al., 2016). Most of the previously published models have been
based on differential equations. Population dynamic models expressed in terms of differential
equations use summarized information regarding a population (e.g. the mean of the population
characteristic) (Osgood, 2009). However, many modeling problems often require considering the
variation in the characteristics of individuals in the population (Osgood, 2009), as well as
statistical uncertainty in the estimated parameters used to describe those characteristics. Agentbased modeling (ABM), is a powerful computer simulation methodology that has only recently
been used to model stray companion animal population dynamics (Yoak et al., 2016, Ireland and
Miller, 2016), and until this thesis, had not been employed to model owned dog population
dynamics. Agent-based models have the ability to incorporate individual-level heterogeneity.
Owned dog’s individual characteristics (e.g. sex, age), and behaviour (e.g. free-roaming) will
contribute differently to the dog population dynamics (e.g. reproduction, mortality, immigration,
and emigration). Therefore, incorporating these individual characteristics and behaviour into the
model can help describe the dog population dynamics in a more biologically relevant manner.
These characteristics and behaviours are especially important to incorporate into the model as
they also influence the projected impact of the proposed dog population control measures. For
example, surgical sterilization targeted at young animals (before they reach sexual maturity),
may be less effective in dog populations which have high mortality rates in young animals,
compared to those where young dogs have lower mortality rates. In the former case, it may be an
inappropriate use of resources to include young dogs in targeted dog reproduction control
interventions.
Furthermore stochastic, agent-based models are more conservative in their
143
predictions given that they account for uncertainty and examine a range of possible outcomes.
For these reasons, agent-based modeling is particularly useful for studying dog population
dynamics in developing countries, where the characteristics and behaviours of dogs and their
owners are highly heterogeneous.
Villa de Tezontepec is a municipality located in the state of Hidalgo in central-eastern
Mexico, with an estimated human population of 11,746 (National Institute of Statistics and
Geography (INEGI), 2010). The municipal government of Villa de Tezontepec has consulted
with the Ministry of Health regarding their dog overpopulation concerns. The research
comprising this thesis was conducted to better understand the local dog population situation and
evaluate the impact of different strategies for dog population control in this community.
As such, the primary objectives of this thesis were:
1. To characterize the dog ecology and demography in Villa de Tezontepec, Hidalgo,
Mexico.
2. To develop an agent-based model to describe the population dynamics of owned dogs
in Villa de Tezontepec, and to determine the projected impact of surgical
reproduction control interventions (focused on dogs of different ages and with varied
surgical capacity) and improved dog confinement, on the total dog population size.
This thesis is comprised of two independent but complementary studies: (1) a crosssectional study aimed at characterizing the dog ecology and demography in Villa de Tezontepec,
Hidalgo (Chapter 2), and (2) an agent based-model to describe and characterize the projected
long-term impact of surgical sterilization interventions and increased dog confinement on the
dog population size for the same community (Chapter 3).
The cross-sectional study (Chapter 2) was conducted in Villa de Tezontepec, Hidalgo,
144
Mexico, from September to December, 2015. Individuals from 328 households were
interviewed. More than half (65%) of the households in Villa de Tezontepec owned dogs, the
majority (58%) of owned dogs were males, and most owned dogs (74%) were older than a year.
The sex distribution and age structure of a dog population are important characteristics that
describe the individual-scale heterogeneity found within population. The study reported that less
than half (45%) of owned dogs were kept confined when unsupervised. High numbers of owned
free-roaming dogs can have a negative impact on public health and dog welfare, and can also
have an effect on the success of free-roaming dog population control interventions (Reece, 2005;
Jackman and Rowan, 2007). Only 37% of the female dogs were spayed and 14% of the male
dogs had been neutered. The information on owned dog demography provided by this study will
be provided to the local government for use in the planning, implementation, and monitoring of
effective dog population control interventions in this region. The data collected during this study
were also used to parameterize an agent-based computer simulation model to assess the potential
impact of different dog population control programs in this community (Chapter 3).
In the second study, a stochastic, agent-based computer simulation model was developed
based on the empirical data collected in the first study that described the characteristics of the
owned dog population in Villa de Tezontepec, Hidalgo in 2015. The model was used to evaluate
the potential impact of performing surgical sterilization on dogs of different ages and at different
levels of monthly surgical capacity. In addition, the model was used to evaluate the potential
impact of increased dog confinement on the total dog population size over a 20-year time period.
The model results indicated that continuing with the current government spay and neuter
program (21 surgeries per month distributed across all age groups) would reduce the overall dog
population size by 14% over a 20-year period. Increasing the number of mixed age sterilizations
145
per month (to 42 or 84 surgeries per month) could potentially result in a much higher dog
population size reduction (range = -46.7% to -78.7%). However, the sustainability of increases in
surgical capacity for the sterilization program may be infeasible for a single region due to its cost
and requirement of resources. Our model findings also suggest that the sterilization of young
dogs (before they reach sexual maturity) could enhance the efficacy of the current surgical dog
population control program for this community, without having to invest in additional resources.
For example, our model projected a population size reduction of 81% after 20 years, when young
dogs were targeted for sterilization at a low (current) surgical capacity level (21 surgeries
performed per month). The model also indicated that if the proportion of confined dogs was 70%
or greater, the population size may decline considerably presumably by preventing the
unintentional reproduction of owned dogs. Achieving such a high rate of confinement is likely
not possible; hence, confinement should be used in combination with other population control
measures. Indeed, the model results indicate that concurrent surgical sterilization and increased
dog confinement interventions are projected to be more effective than either surgical sterilization
or dog confinement interventions alone.
In general, this research illustrates that agent-based models parameterized using empirical
dog population data collected in the field can help to better identify the conditions under which
different types of dog population control interventions may or may not be successful. Agentbased computer simulation models can help to guide decision-making under uncertainty.
Furthermore, these model projections are useful for helping to optimize the limited resources
allocated for dog population control programs within this region. Overall, this thesis highlights
important considerations for the design of improved dog population control programs.
146
4.2. Study limitations
Several limitations of the work presented should be noted. The cross-sectional study was
focused only on owned dogs, which make up only a portion of the total dog population.
Additional information on the non-owned dog population would be useful in modeling how the
dynamics of the entire dog population, and how owned and non-owned dog interactions impact
the population. Another limitation in this study was that the four study neighbourhoods were not
randomly selected and instead were sampled based on their proximity to the capital. These
neighbourhoods may be more highly populated and have higher household density than the other
neighbourhoods in this region (INEGI, 2010), which may limit the extrapolation of results to
other neighbourhoods and communities.
Limitations are also important to consider for the agent-based model developed. The
model was based only on the owned dog population (for which we had data), and excluded stray
and feral dogs. Therefore, the simulation results of this model do not reflect the impact of dog
population control interventions on the overall dog population size for this community. However,
currently, all surgical sterilization interventions performed by the local government in this region
are exclusively targeted at owned male and female pets, from six weeks of age (Secretaria de
Salud, 2015). For this reason, this model only focuses at interventions directed at owned dogs.
Another limitation of this model is the lack of detailed data regarding the mortality rates and
pregnancy rates of unconfined dogs in this community. Unconfined dogs were assumed to have a
higher risk of pregnancy, as described by the empirical data (Kisiel et al., unpublished data) and
to have a higher risk of mortality (Fielding, 2010) than confined dogs. For the agent-based
model, unconfined owned dogs were assumed to have double the pregnancy and mortality annual
rates, than confined dogs. This assumption could have impacted the model results in two ways.
147
First, an over-estimated pregnancy rate results in underestimation of the effectiveness of the
surgical interventions. Second, if the annual mortality was over-estimated, the effectiveness of
the population control measures would be over-estimated. To investigate the potential impact of
the choice of parameter values, we conducted wide-ranging sensitivity analyses. Our findings
suggest that changes in these parameter values within reasonable, biological ranges (Morales and
Ibarra 1979; Ibarra et al., 1991; Morales et al., 1992; Ibarra et al., 1997), had limited impact on
the relative benefit of the different interventions being examined, and did not change the ranking
of the different intervention strategies.
4.3. Key recommendations for the local community
A number of key recommendations for Villa de Tezontepec (and potentially, similar
communities) can be derived from the results of this research:
1. Targeting younger dogs for sterilization could enhance the success of existing dog
population control programs that sterilize mixed age groups without having to invest
in additional surgical resources (e.g. by redistributing the current surgical capacity to
younger dogs).
2. Confinement of owned dogs has the ability to affect the dog population size but
requires a high level of public compliance. Dog population control programs that
include education and/or legislation to prevent owned dogs from being permitted to
roam-freely could contribute to a reduced dog population size.
3. Lastly, reducing the proportion of female dogs becoming pregnant is another way to
reduce the population size over the long term. Dog owners should be discouraged
from intentionally breeding their female dogs and encouraged to limit opportunities
148
that allow for unintentional breeding (e.g. by confining their female dogs when in
heat).
4.4. Recommendations and future directions for research
The findings of this thesis suggest several areas for future research.
1. Current dog population data are very important for the development of accurate
agent-based computer simulation models aimed at evaluating dog population control
interventions. For this reason, when possible, ecologic and demographic data should
be collected from the region of interest to inform these simulation models.
Specifically, the following data should be collected: population size, sex and age of
dogs, mortality and pregnancy (or birth) rates (for both confined and unconfined
dogs), litter sizes, and rate of canine immigration and emigration to/from the
community (Baquero et al., 2016).
2. Further research is needed to understand the economic and cultural motivation of
intentional dog breeding, as well as the reason for the lack of dog confinement and
surgical sterilization observed in this community (and other similar communities).
Understanding these motivations can help establish background information that
could be used in the design of educational campaigns aimed at removing the barriers
(e.g. misconceptions, lack of information) that prevent dog owners from participating
in dog population control programs.
3. The model suggested that an increase in the proportion of owned dogs that are
confined could enhance the impact of the current surgical interventions. To the
author’s knowledge, there are currently no published studies regarding the use and
effectiveness of interventions aimed at increasing the confinement of owned dogs in
149
this community or other semi-urban communities in Mexico. Further research is
necessary to determine the feasibility and sustainability of such interventions.
4. This agent-based simulation model could be expanded to incorporate the freeroaming, non-owned dog population (e.g. stray and feral dogs) to evaluate the impact
that dog population control activities could have on the total dog population (owned,
stray, and feral) for this community.
5. This model could also be expanded to evaluate the effect of non-surgical dog
sterilization
programs
(e.g.
hormonal
methods,
immunocontraceptives,
chemosterilants) to investigate the effectiveness of such dog population reproduction
programs in semi-urban communities.
150
4.5 References
Acosta-Jamett, G., Cleaveland, S., Cunningham, A.A., Bronsvoort, B.M., 2010. Demography of
domestic dogs in rural and urban areas of the Coquimbo region of Chile and implications
for disease transmission. Prev. Vet. Med., 94, 272–281.
Amaku, M., Dias, R.A., Ferreira, F., 2009. Dinâmica populacional canina: potenciais efeitos de
campanhas de esterilização. Rev. Panam. Salud Publica., 25(4), 300-304.
Amaku, M., Dias, R.A., Ferreira, F., 2010. Dynamics and control of stray dog populations. Math.
Popul. Stud., 17, 69-78.
Baquero, O.S., Akamine, L.A., Amaku, M., Ferreira, F., 2016. Defining priorities for dog
population management through mathematical modeling. Prev. Vet. Med., 123, 121-127.
Coleman P. G., 1997. The importance of dog demography to the control of rabies. Proceedings
of the Southern and Eastern African Rabies Group (SEARG)
Meeting, 180.
Downes, M., Canty, M.J., More, S.J., 2009. Demography of the pet dog and cat population on
the island of Ireland and human factors influencing pet ownership. Prev. Vet. Med., 92,
140-149.
Fielding W. J., 2010. Dog Breeding in New Providence, The Bahamas, and its potential impact
on the roaming dog population I: Planned and accidental. J. Appl. Anim. Welf. Sci., 13,
250-260.
Ibarra, L., Núñez, F., Cisternas, P., Méndez, P., 1991. Demografía canina y felina en la Comuna
de la Granja, Santiago, Chile. Avances Cien. Vet., 6.
Ibarra, L., Cisternas, P., Valencia, J., Morales, M.A., 1997. Indicadores poblacionales en caninos
y felinos y existencias de otras especies domésticas en la comuna de El Bosque, Región
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Metropolitana, Chile. Avances Cien. Vet., 12.
Instituto Nacional de Administracion Publica A.C. (INAP), 2009. Guias tecnicas municipales,
2009. Mexico.
Instituto Nacional de Estadistica, Geografia e Informatica (INEGI), 2010. Censo general de
poblacion y vivienda, 2010. Mexico
Ireland, T., Miller, R.N., 2016. A spatial agent-based model of feral cats and analysis of
population and nuisance controls. Ecol. Model., 337, pp.123-136.
Jackman, J., Rowan, A., 2007. Free-roaming dogs in developing countries: the benefits of
capture, neuter and return programs. In: Salem, D.J., Rowan, A.N. (Eds.), The State of
the Animals IV: 2007. Humane Society Press, Washington, pp. 55–78.
Morales M.A. Ibarra L., 1979. Fertilidad y mortalidad en la poblacion canina. Arch. Med. Vet.,
10, 161-164.
Morales, M.A., Urcelay, S., Núñez, F., Cabello, C., 1992. Características demográficas de una
población canina rural en el área nororiente de la región metropolitana. Chile. Avances
Cien. Vet 7.
Morters, M.K., McKinley, T.J., Restif, O., Conlan, A.J.K., Cleaveland, S., Hampson, K., Whay,
H.R., Damriyasa, I.M., Wood, J.L.N., 2014. The demography of free-roaming dog
populations and applications to disease and population control. J. Appl. Ecol., 51, 10961106.
Osgood, N., 2009. Lightening the performance burden of individual‐based models through
dimensional analysis and scale modeling. Syst. Dyn. Rev., 25, 101-134.
Patronek, G.J., Rowan, A.N., 1995. Determining dog and cat numbers and population dynamics.
Anthrozoös, 4, 199–205.
152
Perry, B.D., 1993. Dog ecology in eastern and southern Africa implications for rabies control.
Onderstepoort J. Vet. Res., 60, 429–436.
Reece, J.F. (2005). Dogs and dog control in developing countries. In D.J. Salem & A.N. Rowan
(Eds.), The state of the animals III: 2005 (pp. 55-64). Washington, DC: Humane Society
Press.
Salamanca, C.A., Polo, L.J., Vargas, J., 2011. Sobrepoblación canina y felina: tendencias y
nuevas perspectivas. Rev. Facultad Med. Vet. Zootec., 58, 45-53.
Secretaria de Salud, 2015. Lineamientos generales operativos intensivos para la esterilizacion
quirurgica de perros y gatos mediante cirugias de abordaje simplificado poco invasivo,
2015. Mexico.
Wandeler, A.I., 1985. Ecological and epidemiological data requirements for the planning of dog
rabies control. In: Kuwert, E., Merieux, C., Koprowski, H., Bogel, K. (Eds.), Rabies in
the Tropics. Springer, Berlin, pp. 657–661.
World Health Organization(WHO), 1987. Guidelines for dog rabies control. World Health
Organization, Geneva (VPH/ 83.43).
World Health Organization/World Society for the Protection of Animals (WHO/WSPA), 1990.
Guidelines for dog population management. WHO Document WHO/ZOON/90.165,
Geneva, pp. 1–116.
World Organization for Animal Health (OIE), 2016. Stray dog population control. Terrestrial
Animal Health Code.
Yoak, A.J., Reece, J.F., Gehrt, S.D., Hamilton, I.M., 2016. Optimizing free-roaming dog control
programs using agent-based models. Ecol. Model., 341, 53-61.
153
APPENDIX A
Owned dog ecology and demography in Villa de Tezontepec, Hidalgo, Mexico.
154
A.1. Villa de Tezontepec – HOUSEHOLD Questionnaire Identifiers
Survey #: _____________________
Informed consent to interview obtained
£
Name of person being interviewed: ___________________________________________
Household address: _____________________________________________________
155
A.2. Villa de Tezontepec – HOUSEHOLD Questionnaire
Interviewer Name: _____________________
Consent Date:_________________________
1.
Consent Time: ________________
PART A
Age of the person being interviewed (>18 yrs.):____________ Gender _______________
2.
Household Type (please check one):
Single family house
Multiple family house
Apartment
Farmhouse
Other (specify): _______________________________
3.
Household Ownership (please check one):
Own
Rent
Other (specify): _______________________________
4.
Is the household fully enclosed (walled or fenced)? Check one: ____ Yes _____ No
If YES, Do you keep your gate regularly closed? Check one: ____ Yes _____ No
5.
How many people live in the household (including children)? _______
Please record the details of the people living in this household in the table below:
Person 1
Person 2
Person 3
Person 4
Person 5
Person 6
Person 7
Person 8
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
Gender
Age
< 5 years
5-9 years
10-17 years
18-50 years
> 50 years
6.
Do you own any livestock? Check one: ____ Yes _____ No
If YES, Please write the number of each type of animal you keep, and check “yes” if they are kept close to your
household living quarters (within 1km):
Number of animals kept
Pigs
Sheep
Goats
Calves
Cows
Chickens
Other(s) (specify): ________________
156
Kept close to house (<1 km)?
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
7.
Do you see any of the following wildlife near your household (within 1km) with in the past month? Please
check all that apply:
Coyotes
Foxes
Raccoons
Badgers
Skunks
8.
How do you dispose of food waste? Please check all that apply:
Disposed together with the non-food garbage
Feed to dog(s)
Feed to other animals
Other (specify): _______________________________
9.
How do you dispose of your non-food garbage? Please check all that apply:
It gets picked up by the municipality garbage collection
It gets taken to public dump by someone in household
Burn it on my own property
Other (specify): _______________________________
10.
If the garbage/food waste is collected by the municipality, how frequently is it collected? Please check all that
apply:
Less than twice a week (specify # days/week) _______
Twice a week
More than twice a week (specify # days/week) ______
Other (specify): _______________________________
11.
Do any dogs have access to your garbage/food waste? Check one: ___Yes ___ No
12.
Do you feed any dogs that you do not own on a regular basis (at least once a week)? Check one: ____ Yes
_____ No
If YES, what is the reason for feeding these dogs? Check all that apply:
I don’t want to throw food scraps into the garbage
I feel sorry for these animals
These animals live in the community
I don’t know
Other (specify): _______________________________
If YES, where do you feed these dogs? Check all that apply:
Outside my property
In the near by park/vacant lot
Other (specify): _______________________________
13.
Do dogs in the community whose owners are unknown regularly (daily) visit your property? Check one: ___
Yes ___ No
If YES, how many_____________
157
If YES, Do you do any of the following? Check all that apply
Feed them
Take them to be vaccinated
Take them to a veterinarian when sick
Other (specify): _______________________________
14.
Please record the details of these dogs.
Dog 1
Dog 2
Dog 3
Dog 4
Dog 5
Dog 6
Dog 7
£
£
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£
Sex
Age
§ Puppy (less than 3 months)
§ Juvenile (3 to 12 months)
§ Adult (more than 12 months)
15.
Has your household ever owned dogs? Check one: ____ Yes _____ No
If NO, go to question 24
16.
Does your family currently own any dogs? Check one: ____ Yes _____ No
If NO, then go to question 24
PART B
17.
How many dogs are there living in this household? #_______
18.
Over the past 12 months, did any of the household’s dogs die or leave the household? Check one: ____ Yes
_____ No
If YES, please record the details of all dogs that have left the household in the last 12 months in the table
below
What sex was
the dog?
What happened to him/her?
1
2
3
4
5
1. Male
1. Sold Inside Villa de Tezontepec
2. Female
2. Sold outside Villa de Tezontepec
3. Don’t know
3. Given away inside Villa de
Tezontepec
4. Given away outside Villa de
Tezontepec
5. Killed by house member
6. Died after being hit by a car
7. Died of disease/parasites
8. Die old age/natural
9. Died of starvation
10. Died – other
(specify)
11. Killed by authorities
12. Killed by someone
else
13. Escape/Got Lost
14. Abandoned
15. Stolen
16. Other (specify)
158
How old was
he/she when this
happened?
19.
Please tell us about your current? dog(s) by completing the following table:
Dog 1
Dog 2
Dog 3
Dog 4
£ Yes £ No
£ Yes £ No
£ Yes £ No
£ Yes £ No
_________
£ Male
£ Female
£ Yes £ No
£ don’t know
£ Yes £ No
_________
£ Male
£ Female
£ Yes £ No
£ don’t know
£ Yes £ No
_________
£ Male
£ Female
£ Yes £ No
£ don’t know
£ Yes £ No
________
£ Male
£ Female
£ Yes £ No
£ don’t know
£ Yes £ No
£
£
£
£
£
£
£
£
£
£
£
£
£ Yes £ No
£ Yes £ No
£ Yes £ No
£ Yes £ No
Name of dog
Did you acquire this dog in the last 12
months?
If yes, please provide the month
Sex
FEMALE ONLY
Is she currently pregnant?
Did she get pregnant in the past 12
months?
If NO, how did you prevent her from
getting pregnant? Please check one.
§ Keep her confined during heat
§ Temporary Contraception
§ She is spayed
§ Other (explain)
Was the pregnancy planned?
If yes, please check one
§ I wanted to sell the puppies
§ I wanted more dogs
§ For my dog’s health/needs
§ Other (specify)
Total # of litters had in her lifetime
How old was she when she had her first
litter?
# litters in the past 12 months
# of puppies in the past 12 months
Please tell us about her most recent
litter (puppies):
§ # of female
§ # of male
§ # of born alive
§ # of born dead
§ # still alive and in the household
§ # died from disease
§ # died from other causes (specify)
£
£
£
_________
£
£
£
_________
£
£
£
_________
£
£
£
_________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
§
# killed by household members
__________
__________
__________
__________
§
# given away for free inside Villa de
Tezontepec
# still alive in other household
__________
__________
__________
__________
__________
__________
__________
__________
# given away for free outside Villa de
Tezontepec
# sold inside Villa de Tezontepec
# sold outside Villa de Tezontepec
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
§
§
§
§
159
§ # abandoned
§ # disappeared
§ # other (specify)
MALE ONLY
Did you purposely mate this dog in the
last 12 months?
If yes, check all that apply:
§ Wanted to sell the offspring
§ Good for his health
§ I do not know
§ Other (explain)
Age of dog when family got it?
§ # years
OR, if exact age unknown
Check one:
§ Puppy (less than 3 months)
§ Juvenile (3 to 12 months)
§ Adult (more than 12) months)
Current age of dog?
§ # years
OR, if exact age unknown
Check one:
§ Puppy (less than 3 months)
§ Juvenile (3 to 12 months)
o
3 – 6 months
o
6 – 12 months
§ Adult (more than 12 months)
o
Less than 3 years
o
3 – 5 years
o
6 – 10 years
o
More than 10 year
Dog’s breed?
§ If known
Check one:
§ Pure-bred
§ Mongrel
§ Don’t know
Reason for owning dog
(Check ALL that apply)
§ Guarding
§ Pet/companion
§ Breeding
§ Herding/protecting livestock
§ Pest control
§ Other (specify):
Dog 1
__________
__________
__________
£ Yes £ No
Dog 2
__________
__________
__________
£ Yes £ No
Dog 3
__________
__________
__________
£ Yes £ No
Dog 4
__________
__________
__________
£ Yes £ No
£
£
£
_________
£
£
£
_________
£
£
£
_________
£
£
£
_________
£
£
£
£
£
£
£
£
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£
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£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
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£
£
£
£
£
£
£
£
£
£
£
£
£
________
£
£
£
£
£
________
£
£
£
£
£
________
£
£
£
£
£
________
160
Source of dog (Check ONE)
§ Pup of owned dog
§ Gift from inside Villa de Tezontepec
§ Gift from outside Villa de Tezontepec
§ Bought inside Villa de Tezontepec
o From other owner
o From store/market
o Other
§ Bought outside Villa de Tezontepec
§ Adopted
§ Found from the street
§ Other (specify):
Who looks after the dog (e.g. feeds,
gives water, pick up feces)?
(Check ALL that apply)
§ Respondent
§ Adults in household
§ Children in household
§ No one
§ Don’t know
Was this dog given fresh water in the
past two days?
How often is the dog fed?
§ Twice a day or more
§ Once per day
§ Once every 2 days
§ Less frequent that once every 2 days
§ Don’t know
How is the dog fed? (Check ALL that
apply)
§ By household– dog food
§ By household – scraps
§ By neighbors
§ Household garbage
§ Garbage dump
§ Waste in street
§ Market / butcher waste
§ Hunting
§ Other (specify):
Receives veterinary care?
§ Never
§ Only when get sick/hurt
§ Other (specify)
Treated for external parasites (e.g.
fleas) in the past 12 months?
Dog 1
Dog 2
Dog 3
Dog 4
£
£
£
£
£
£
£
_________
£
£
£
________
£
£
£
£
£
£
£
_________
£
£
£
______
£
£
£
£
£
£
£
_________
£
£
£
________
£
£
£
£
£
£
£
_________
£
£
£
________
£
£
£
£
£
£ Yes £ No
£ don’t know
£
£
£
£
£
£ Yes £ No
£ don’t know
£
£
£
£
£
£ Yes £ No
£ don’t know
£
£
£
£
£
£ Yes £ No
£ don’t know
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
_________
£
£
£
£
£
£
£
£
_________
£
£
£
£
£
£
£
£
_________
£
£
£
£
£
£
£
£
_________
£
£
_________
£ Yes £ No
£ don’t know
£
£
_________
£ Yes £ No
£ don’t know
£
£
_________
£ Yes £ No
£ don’t know
£
£
_________
£ Yes £ No
£ don’t know
161
Dewormed in the past 12 months?
Visited a veterinarian in the past 12
months?
If yes, provide the reason
Do you take this dog for walk?
If YES, how do you control it?
Leashed
Unleashed
Vaccinated for rabies in the past 12
months?
Was the dog vaccinated in this year
2015? If YES, In which vaccination
campaign?
§ March
§ September
On average, when is your dog confined
to your property? (Check ONE)
§ Never confined / free to roam
§ During daylight only
§ During night only
§ Always (day and night)
§ Sometimes
§ Don’t know
Access to housing when confined?
§ Yes, all the time
§ Yes, but not all the time
§ No
§ Don’t know
Allowed inside your home (Bedroom,
living room, kitchen etc.?
Keep it tied/chained?, If YES, for how
long?
§ Yes, all the time
§ Yes, but not all the time
§ No
§ Don’t know
Has this dog bitten a person?
Has this dog bitten another dog?
Wears a Collar?
Spayed/Neuter?
Dog 1
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
___________
£ Yes £ No
Dog 2
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
___________
£ Yes £ No
Dog 3
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
___________
£ Yes £ No
Dog 4
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
___________
£ Yes £ No
£
£
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
£
£
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
£
£
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
£
£
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£ Yes £ No
£ Yes £ No
£ Yes £ No
£ Yes £ No
£ Yes£ No
£ Yes £ No
£ Yes £ No
£ Yes £ No
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
£ Yes £ No
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
£ Yes £ No
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
£ Yes £ No
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
£ Yes £ No
£ don’t know
£ Yes £ No
£ Yes £ No
£ don’t know
162
Dog 1
If YES, where it was spayed/neutered?
§ Government campaign
§ Private veterinarian Clinic
§ Don’t know
§ Other (specify)
GO TO QUESTION 25
If NO, why not?
§ Don’t know what is involved or how
to get it done
§ Transportation/scheduling problems
§ Too expensive/don’t have the money
right now
§ Risk of the surgery/suffering of dogs
§ Keep it in good health
§ Want to breed to sell offspring
§ Don’t know
§ Other (specify)
GO TO QUESTIONS 20- 22
20.
£
£
£
_________
£
£
£
_________
£
£
£
_________
£
£
£
_________
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
_________
£
_________
£
_________
£
_________
_____Yes
_____ No If no, please explain:
_____Yes
_____ No If no, please explain:
Would you neuter a male dog if a non-surgical option was available?
Check one:
23.
Dog 4
Would you have a veterinarian apply a short-term temporary contraceptive (e.g. 2 year) into your female dog
if option was available?
Check one:
22.
Dog 3
Would you spay a female dog if a non-surgical option was available?
Check one:
21.
Dog 2
_____Yes
_____ No If no, please explain:
Would you register/license your pet with the municipality, if this option was available?
Check one:
_____Yes
_____ No If no, please explain:
24.
Why do you not own any dogs? Check all that apply:
Don’t like them
They require too much time/work/money
Don’t have space
Afraid of dogs
Just don’t have one right now, but plan to get one
Don’t know
Other (specify): _______________________________
25.
Do you plan to get a dog in the next 12 months? Check one: ____ Yes _____ No
163
26.
Do you own any pets other than dogs? Check one: ____ Yes _____ No
If YES, please write the number of each type of pet other than dogs that you keep:
____ Cats
____ Fish
____ Birds
____ Other Specify _________
27.
Have you had any unpleasant experiences with street dogs (e.g. bites)? Check one: ____ Yes _____ No
If YES, please check all that apply:
Bitten
Got chased but not bitten
Hit a dog while driving a car
Witness an animal cruelty event
Other (specify): _______________________________
28.
How do you usually respond to street dogs in your neighborhood? Please check all that apply:
Feed them
Try to locate their owner
Try to ignore/hope they go away
Try to drive them away (shouting, throwing rocks, etc.)
Poison
Call the municipality/animal control
Other (specify): _______________________________
29.
Please indicate your level of agreement with each of the following statements:
“Street dogs should be killed by the authorities.”
Agree
Neither agree
nor disagree
Disagree
£
£
£
“Street dogs should be left on the streets, and cared for by the community.”
Agree
Neither agree
nor disagree
Disagree
£
£
£
“Street dogs should be spayed/neutered, and then returned to the streets.”
Agree
Neither agree
nor disagree
Disagree
£
£
£
164
30.
Has anyone in your family been bitten by a dog in the last 12 months (since October 2014), while physically
in Villa de Tezontepec? Check one: ____ Yes _____ No
If NO, go to question 32
31.
Please describe the dog bite by completing the following table:
Person
Bitten
Person
age
when
bitten
Gender
Do you
know
why the
dog bit?
How the
bite was
treated
(include
all)
1. Head/
Neck
1. Yes
Reason:
_______
1. Wash the
wound with
water only
1. Yes
1. Died
2. On the
street
2.Hands/
Arms
2. No
2. Wash the
wound with
soap/water
2. No
2. Killed
3. Other
(specify)
3. Feet/
Legs
3. Don’t
know
3. Go to the
health
center/hosp
ital
4. Nothing
3. Don’t
know
3. Ran away
Bitten by
which
dog?
Place
where
bitten
Part of
body
bitten
1.Our
household
dog
1. Inside
a House
2. Strange
dog not
regularly in
our
community
3. A dog
regularly in
our
community
4. A
neighbor’s
dog
5. Don’t
know
6. Other
(specify)
Received
Rabies
Treatment
Fate of the
biting dog
1
2
3
4
32.
4. Trunk
5. Other
(specify)
5. Don’t
know
6. Other
(specify)
5. Don’t
know
6. Other
(specify)
Please indicate your level of agreement with the following statement:
“The street dogs in my community pose physical risks to people (e.g. bites).”
Agree
Neither agree
nor disagree
Disagree
£
£
£
“The street dogs in my community can transmit infections to people.”
Agree
Neither agree
nor disagree
Disagree
£
£
£
165
4. Still Alive
“There are too many street dogs in my community.”
33.
Agree
Neither agree
nor disagree
Disagree
£
£
£
How often are you or your family members frightened by street dogs in your community?
Always
£
34.
Very Often
£
Sometimes
£
Very Rarely
£
Never
£
What is the household monthly income? (Note: This information is important to allow us to understand
whether household economics have an effect in dog ownership). Please check one:
£
£
£
£
£
£
From
$0
to
$ 2,699.00
From
$ 2,700.00
to
$ 6,799.00
From
$ 6,800.00
to
$ 11,599.00
From $ 11,600.00
to
$ 34,999.00
From $ 35,000.00
to
$ 84,999.00
From $ 85,000.00
or
More
166
A.3. Villa de Tezontepec – Cuestionario HOGAR Identificadores
Encuesta #: _____________________
Consentimiento informado para la entrevista obtenido £
Nombre de la persona entrevistada: ___________________________________________
Dirección de la casa: _____________________________________________________
167
A.4. Villa de Tezontepec - Cuestionario HOGAR
Nombre de Entrevistador: ___________________________________________
Fecha: _______________________________
35.
Hora: ____________________
PARTE A
Edad de la persona entrevistada (> 18 años): _______________ Sexo ____________
36.
Tipo de Casa (marque uno):
Casa de una sola familia
Casa de múltiples familias
Casa en interior de vecindad o departamento en condominio
Granja
Otra especificar): ______________________________
37.
Propiedad de la Casa (marque uno):
Propia (es dueño)
Rentado
Otra (especificar): ______________________________
38. ¿La casa está completamente bardeada o cercada? Marque uno: ____ Sí _____ No
Si es así, ¿Mantiene su puerta cerrada con regularidad? Marque uno: ____ Sí _____ No
39.
¿Cuántas personas viven en esta casa (incluyendo niños)? _______
Por favor proporcione los detalles de la gente viviendo en esta casa en la tabla de abajo:
Persona Persona Persona Persona Persona Persona
1
2
3
4
5
6
Sexo
Persona
7
Persona
8
£
£
£
£
£
£
£
£
£
£
Edad
<5 años
5-9 años
10-17 años
18-50 años
> 50 años
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
40. ¿Es dueño de cualquier tipo de ganado? Marque uno: ____ Sí _____ No
Si es así, por favor escriba el número de cada tipo de animal que posee, y marque "SI", si los mantiene cerca de su
vivienda (a 1 km):
Numero de animales poseídos
Cerdos
Borregos
Cabras
Terneros
Vacas
Pollos
Otros (especificar): _______________
168
Mantenidos cerca de la casa (<1
km)?
Si
No
Si
No
Si
No
Si
No
Si
No
Si
No
Si
No
¿Ha visto usted alguno de los siguientes animales silvestre cerca de su casa (a 1 km) en el mes pasado? Por favor,
marque TODOS los que apliquen:
Coyotes
Zorros
Mapaches
Tejones
Zorrillos
41.
¿Cómo se deshace de sus desperdicios de comida? Por favor, marque TODOS los que apliquen:
Los tira junto con la otra basura
Se los da como alimento a sus o a otros perro(s)
Se los da como alimento a otro tipo de animales
Otra (especificar): _____________________________
42. ¿Cómo se deshace de su basura que no son desperdicios de comida? Por favor, marque TODOS los que
apliquen:
Es recogida por la recolección de basura municipal
Es llevada al basurero público por alguien de la casa.
La quemo en mi propia casa.
Otra (especificar): _______________________________
43. Si la basura / desperdicios de comida son recogidos por el municipio, con qué frecuencia son recogidos? Por
favor, marque TODOS los que apliquen:
Menos de dos veces por semana (especificar # días/semana) ____
Dos veces por semana
Más de dos veces por semana (especificar # días/semana) _____
Otra (especificar): _______________________________
44.
¿Hay perros que tienen acceso a su basura/botes de basura? Marque uno: ___Si ___ No
45. ¿Alimenta regularmente (al menos una vez a la semana) a algún perro(s) del cual no es su dueño Marque
uno: ____ Sí _____ No
Si es así, ¿Cuál es la razón por la que alimenta a este perro(s)? Marque TODOS los que apliquen:
No quiero tirar las sobras de comida en la basura
Me dan pena estos animales
Estos animales viven en la comunidad
No lo sé
Otra (especificar): _______________________________
Si es así, ¿En dónde alimenta a estos perros? Marque TODOS los que apliquen:
Afuera de mi propiedad
En un parque / lote baldío cercano
Otra (especificar): _______________________________
46. ¿Hay perros de la comunidad cuyos propietarios son desconocidos que visiten regularmente (diariamente) su
propiedad? Marque uno: ___ Sí ___ No
Si es así, ¿Cuántos?_____________
169
Si es así, ¿Realiza algo de lo siguiente? Marque TODOS los que apliquen:
Alimentarlos
Llévelos a ser vacunado
Llévelos a un veterinario cuando están enfermos
Otra (especificar): _______________________________
47.
Por favor anote los detalles de estos perros.
Sexo
Edad
§ Cachorro (menos de 3 meses)
§ Juvenil (de 3 a 12 meses)
§ Adulto (más de 12 meses)
48.
Perro
1
Perro
2
Perro
3
Perro
4
Perro
5
Perro
6
Perro
7
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
¿Ha tenido en su casa alguna vez un perro(s)? Marque uno: ____ Sí _____ No
SI NO, PASE A LA PREGUNTA 24
49.
¿Su familia tiene actualmente perro(s)? Marque uno: ____ Sí _____ No
Si NO, PASE A LA PREGUNTA 24
PARTE B
50.
¿Cuántos perros viven en esta casa? #____________
51. En los últimos 12 meses, ¿alguno de los perros del hogar murió o fue abandonado? Marque uno: ____ Sí
_____ No
Si es así, escriba los datos de todos los perros adultos que han dejado el hogar en los últimos 12 meses en la
tabla de abajo
¿Que
sexo
tenía?
¿Qué pasó con él / ella?
1
2
3
4
5
1. Macho
2.
Hembra
3. No
sabe
1. Vendido dentro de Villas de Tezontepec
2. Vendido afuera de Villas de Tezontepec
3. Regalado dentro de Villas de
Tezontepec
4. Regalado afuera de Villas de
Tezontepec
5. Matado por miembro de la casa
6. Murió atropellado por un carro
7. Murió de enfermedad / parásitos
8. Murió de viejo / naturalmente
170
9. Murió de hambre
10. Murió otra
(especificar)
11. A Matado por las
autoridades
12. Matado por alguien
más
13. Escapo / Perdió
14. Abandonado
15. Robado
16. Otras (especificar)
¿Qué edad tenia
el/ ella cuando esto
sucedió?
52.
Háblenos de su perro(s) actual, por favor complete el siguiente cuadro:
Perro 1
Perro 2
Nombre del perro
¿Adquirió este perro en los últimos 12
meses?
Si es así, indique el mes
Sexo
HEMBRAS SOLAMENTE
¿Está preñada?
§
§
§
§
¿Estuvo preñada en los últimos 12
meses?
Si NO, ¿Cómo evitó que ella quedara
preñada? Por favor, marque uno:
La mantengo encerrada durante el celo
Anticoncepción Temporales
Ella está esterilizada
Otros (especificar):
§
§
¿Fue la preñez planeada?
Si es así, por favor marque uno:
Quería vender crías
Quería más perros
Por la salud/necesidades de mi perro
Otra (especificar):
# Total de camadas que ha tenido en su
vida
¿Qué edad tenía cuando tuvo su
primera camada?
# camadas en los últimos 12 meses
# De cachorros en los últimos 12 meses
Háblenos de su camada más recientes
(cachorros):
# De hembras
# De machos
# Nacidos vivos
# Nacidos muertos
# Sigue vivo y en la casa
# Murió a causa de una enfermedad
# Murió por otras causas (especificar)
# Matado por miembros del casa
# Regalados dentro de Villa de
Tezontepec
# Siguen vivos en otro hogar
# Regalados fuera de Villa de Tezontepec
§
# Vendidos dentro de Villa de Tezontepec
§
# Vendidos fuera de Villa de Tezontepec
§
§
§
§
§
§
§
§
§
§
§
§
§
Perro 3
Perro 4
£ Sí £ No
£ Sí £ No
£ Sí £ No
£ Sí £ No
_________
£ Macho
£ Hembra
_________
£ Macho
£ Hembra
_________
£ Macho
£ Hembra
________
£ Macho
£ Hembra
£ Sí £ No
£ No se
£ Sí £ No
£ Sí £ No
£ No se
£ Sí £ No
£ Sí £ No
£ No se
£ Sí £ No
£ Sí £ No
£ No se
£ Sí £ No
£
£
£
£
£
£
£
£
£
£
£
£
£ Sí £ No
£ Sí £ No
£ Sí £ No
£ Sí £ No
£
£
£
_________
£
£
£
_________
£
£
£
_________
£
£
£
_________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
_________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
__________
171
§
§
§
§
§
§
§
§
§
§
§
§
§
§
o
o
§
o
o
o
o
§
§
§
§
§
§
§
§
§
§
# Abandonados
# Desaparecidos
# Otra (especificar):
MACHOS SOLAMENTE
¿Usted cruzo intencionalmente a este
perro en los últimos 12 meses?
Si es así, marque TODOS los que apliquen:
Quería vender la descendencia
Bueno para su salud
No lo sé
Otros (especificar):
TODOS
Edad del perro cuando la familia lo
obtuvo
# años
O si la edad exacta es desconocida. Marque
uno:
Cachorro (menos de 3 meses)
Juvenil (de 3 a 12 meses)
Adultos (más de 12meses
Edad actual de perro
# años
O, si la edad exacta es desconocida.
Marque uno:
Cachorro (menos de 3 meses)
Juvenil (de 3 a 12 meses)
3 - 6 meses
6 - 12 meses
Adultos (más de 12 meses)
Menos de 3 años
3 - 5 años
6 - 10 Años
Más de 10 años
Raza del perro
Si se conoce
Marque uno:
De raza
Mestizo
No se
Razón por la que es propietario del perro
Marque TODOS los que apliquen:
Guardia
Mascotas / compañía
Cría (venta)
Trabajo/Protección del ganado
Control de plagas
Otra (especificar):
Perro 1
__________
__________
__________
Perro 2
__________
__________
__________
Perro 3
__________
__________
__________
Perro 4
__________
__________
__________
£ Sí £ No
£ Sí £ No
£ Sí £ No
£ Sí £ No
£
£
£
_________
£
£
£
_________
£
£
£
_________
£
£
£
_________
_________
_________
_________
_________
£
£
£
£
£
£
£
£
£
£
£
£
_________
_________
________
_________
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
_________
_________
_________
_________
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
________
£
£
£
£
£
________
£
£
£
£
£
________
£
£
£
£
£
________
172
Origen de perro Marque uno:
Cachorro de un perros propio
Regalo del interior de Villa de Tezontepec
Regalo de fuera de Villa de Tezontepec
§
§
§
§
o
o
o
§
§
§
§
§
§
§
§
§
§
§
§
§
§
§
§
§
§
§
§
§
§
§
§
§
§
Comprado dentro de Villa de Tezontepec
De otro propietario
De tienda/mercado
Otro
Comprado fuera Villa de Tezontepec
Adoptado
Encontrado en la calle
Otra (especificar):
¿Quién se ocupa del perro?
(por ejemplo, alimentos, da agua,
recoger las heces)?
Marque TODOS los que apliquen:
El respondiente
Los adultos en el hogar
Los niños en los hogares
Ninguno
No se
¿Le dio agua fresca a este perro en los
pasados 2 días?
¿Con qué frecuencia alimenta al perro?
Dos veces al día o más veces
Una vez al día
Una vez cada 2 días
Menos frecuente que una vez cada 2 días
No se
¿Cómo se alimenta el perro? Marque
TODOS los que apliquen:
Por el hogar- comida de perros
Por el hogar - sobras
Por vecinos
La basura del hogar
Basurero
Residuos en la calle
Residuos Mercado / carnicero
Caza
Otra (especificar):
¿Recibe atención veterinaria?
Nunca
Sólo cuando se enferman/herido
Otra (especificar):
¿Ha sido tratado contra parásitos
externos (por ejemplo, pulgas) en los
últimos 12 meses?
Perro 1
Perro 2
Perro 3
Perro 4
£
£
£
£
£
£
£
£
£
£
£
£
£
£
________
£
£
£
________
£
£
________
£
£
£
________
£
£
________
£
£
£
________
£
£
________
£
£
£
________
£
£
£
£
£
£ Sí £ No
£ No se
£
£
£
£
£
£ Sí £ No
£ No se
£
£
£
£
£
£ Sí £ No
£ No se
£
£
£
£
£
£ Sí £ No
£ No se
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
_________
£
£
£
£
£
£
£
£
_________
£
£
£
£
£
£
£
£
_________
£
£
£
£
£
£
£
£
_________
£
£
_________
£ Sí £ No
£ No se
£
£
_________
£ Sí £ No
£ No se
£
£
_________
£ Sí £ No
£ No se
£
£
_________
£ Sí £ No
£ No se
173
§
§
§
§
§
§
§
§
§
§
§
§
§
§
§
§
¿Ha sido desparasitado en los últimos 12
meses?
¿Ha visitado a un veterinario en los
últimos 12 meses?
Si es así, indique la razón
¿Saca a este perro a caminar?
Si es así, ¿cómo es controlado?
Correa
Suelto
¿Ha sido vacunado contra la rabia en los
últimos 12 meses?
¿En este año 2015, el perro ya fue
vacunado? Si es así, En qué campaña de
vacunación?
Marzo
Septiembre
¿En qué momentos tiene a su perro
encerrado en su propiedad? Marque uno:
Nunca está encerrado / vaga libremente
Durante el día solamente
Durante la noche solamente
Siempre (día y noche)
Algunas Veces
No se
¿Tiene acceso a una casa ó refugio
cuando está encerrado?
Si todo el tiempo
Sí, pero no todo el tiempo
No
No se
Le permite entrar al interior de la casa.
(Recamaras, sala, cocina etc.)
¿Lo mantiene amarrado/encadenado? Si
es así, ¿Por cuánto tiempo?
Sí, todo el tiempo
Sí, pero no todo el tiempo
No
No se
¿Este perro ha mordido alguna persona?
Este perro ha mordido algún otro perro?
¿Lleva un collar?
¿Está esterilizado/castrado?
Perro 1
£ Sí £ No
£ No se
£ Sí £ No
£ No se
___________
£ Sí £ No
Perro 2
£ Sí £ No
£ No se
£ Sí £ No
£ No se
_________
£ Sí £ No
Perro 3
£ Sí £ No
£ No se
£ Sí £ No
£ No se
__________
£ Sí £ No
Perro 4
£ Sí £ No
£ No se
£ Sí £ No
£ No se
__________
£ Sí £ No
£
£
£ Sí £ No
£ No se
£ Sí £ No
£ No se
£
£
£ Sí £ No
£ No se
£ Sí £ No
£ No se
£
£
£ Sí £ No
£ No se
£ Sí £ No
£ No se
£
£
£ Sí £ No
£ No se
£ Sí £ No
£ No se
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£ Sí £ No
£ Sí £ No
£ Sí £ No
£ Sí £ No
£ Sí £ No
£ Sí £ No
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£ Sí £ No
£ No se
£ Sí £ No
£ No se
£ Sí £ No
£ Sí £ No
£ No se
£ Sí £ No
£ No se
£ Sí £ No
£ No se
£ Sí £ No
£ Sí £ No
£ No se
£ Sí £ No
£ No se
£ Sí £ No
£ No se
£ Sí £ No
£ Sí £ No
£ No se
£ Sí £ No
£ No se
£ Sí £ No
£ No se
£ Sí £ No
£ Sí £ No
£ No se
174
£ Sí £ No
£ Sí £ No
§
§
§
§
§
§
§
§
§
§
§
§
Si es así, ¿Dónde fue esterilizado /
castrado?
Campaña de Gobierno
Clínica veterinaria privada
No se
Otra (especificar):
PASE A LA PREGUNTA 25
Si NO, ¿por qué no?
No sé de qué se trata o cómo lograr que se
haga
Problemas Transporte / horarios
Demasiado caro / no tiene dinero en este
momento
Riesgos de la cirugía / sufrimiento del perro
Mantenerlo en buena salud
Quiere vender las crías
No se
Otra especificar)
PASE A LAS PREGUNTAS 20 - 22
53.
Perro 1
Perro 2
Perro 3
Perro 4
£
£
£
_________
£
£
£
_________
£
£
£
_________
£
£
£
_________
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
_________
£
£
£
_________
£
£
£
_________
£
£
£
_________
¿Esterilizaría a una perra hembra si una opción no quirúrgica estuviera disponible?
Marque uno:
_____Si _____ No
Si No, por favor explique:
54. ¿Haría que que un veterinario aplicará un anticonceptivo temporal de corto plazo (por ejemplo, 2 años) en su
perra si la opción estuviera disponible?
Marque uno:
55.
Si No, por favor explique:
¿ Castraría a un perro macho, si una opción no quirúrgica estuviera disponible?
Marque uno:
56.
_____Si _____ No
_____Si _____ No
Si No, por favor explique:
¿Registraría/sacaría un licencia para su mascota con el municipio, si esta opción estuviera disponible?
Marque uno:
_____Si _____ No
Si No, por favor explique:
PASE A LA PREGUNTA 26
57.
¿Por qué no tiene perros? Marque TODOS los que apliquen :
No me gustan
Requieren mucho tiempo / trabajo / dinero
No tengo espacio
Me dan miedo los perros
No tengo uno en este momento, pero planeo conseguir uno
No se
Otra especificar): _______________________________
175
58.
¿Tiene planes de obtener un perro en los próximos 12 meses? Marque uno: ____Sí
59.
¿Su familia tiene otras mascotas que no sean perros? Marque uno:
____Sí
___No
_____No
En caso afirmativo, por favor escriba el número de cada tipo de animal doméstico que no sean perros que mantenga:
____ Gatos
____ Peces
____ Aves
____ Otra (especificar); _________
60.
Sí
¿Ha tenido alguna experiencia desagradable con perros callejeros (Ejemplo mordidas)? Marque uno:
_____ No
____
En caso afirmativo, por favor marque TODOS los que apliquen:
Fue Mordido
Lo persiguió un perro pero no lo mordió
Atropello a un perro mientras conducía un automóvil
Presencio un evento de crueldad animal
Otra (especificar): _______________________________
61. ¿Cómo suele actuar cuando ve a perros de la calle en su barrio o colonia? Por favor, marque TODOS los que
apliquen:
Les da de comer
Trata de localizar a su dueño
Trata de ignorar / esperar que se se vayan
Trata de ahuyentarlos (gritando, tirando piedras, etc.)
Los envenena
Llama a la perrera municipal para que los recoja
Otra (especificar): ______________________________
62.
Indique su grado de acuerdo con cada una de las siguientes declaraciones:
“Los perros de la calle deben ser sacrificados por las autoridades."
Está de acuerdo
Le es indiferente
£
£
Está en Desacuerdo
£
"Los perros de la calle se deben dejar en las calles y ser atendidos por la comunidad."
Está de acuerdo
Le es indiferente
Está en Desacuerdo
£
£
£
"Los perros de la calle deben ser esterilizados / castrados, y luego regresados a las calles."
Está de acuerdo
Le es indiferente
Está en Desacuerdo
£
£
£
63. Alguien de su familia ha sido mordido por un perro en los últimos 12 meses (desde octubre de 2014), en Villa
de Tezontepec? Marque uno: ____ Sí _____ No
176
Si NO, pase a la pregunta 32
Persona
mordida
64.
Por favor, describa la mordedura de perro, completando el siguiente cuadro:
Edad de
la
persona
cuando
fue
mordida
Género
Mordido
por qué
perro?
Lugar
donde fue
mordido
Parte del
cuerpo
mordida
¿Sabe
por que
le
mordió
el perro?
¿Cómo se
trató la
mordedura
(incluya
todas las que
apliquen)
Recibo
Tratamiento
contra la
Rabia
Que le paso
al perro que
lo mordió
1. Lave la
herida con
agua
solamente
1. Sí
1. Murió
2. Lave la
herida con
jabón / agua
2. No
2. Fue
Sacrificado
3. Fui al
centro de
salud /
hospital
4. Nada
3. No sabe
3. Escapo
1
2
3
4
1. Por su
propio
perro.
1. Dentro
de una Casa
1. Cabeza /
Cuello
2. Por un
perro
extraño que
no era de la
comunidad.
2. En la
calle
2.Manos/
brazos
3. Por un
perro de la
comunidad.
3. Otros
(especificar
)
1. Sí
Motivo:
2. No
3. Pies /
Piernas
4. Por el
perro de un
vecino.
4. Tronco
5. No sabe
5. Otros
(especificar)
3. No
sabe
6. Otro
(especificar
)
65.
4. Sigue Vivo
5. No sabe
5. No sabe
6. Otro
(especificar)
6. Otros
(especificar)
Indique su grado de acuerdo con la siguientes declaraciones:
"Los perros de la calle de mi comunidad presentan riesgos físicos a las personas (por ejemplo, mordeduras)."
Está de acuerdo
Le es indiferente
Está en Desacuerdo
£
£
£
"Los perros de la calle de mi comunidad pueden transmitir infecciones a las personas."
Está de acuerdo
Le es indiferente
Está en Desacuerdo
£
£
£
"Hay demasiados perros callejeros en mi comunidad."
Está de acuerdo
Le es indiferente
£
£
Está en Desacuerdo
£
177
66. ¿Con qué frecuencia usted o miembros de su familia se sienten atemorizados por los perros de la calle en su
comunidad?
Siempre
Muy a menudo
A veces
Muy raramente
Nunca
£
£
£
£
£
67. ¿Cuál es el ingreso mensual de este hogar? (Nota: Esta información es importante para que podamos entender
si la economía del hogar tienen un efecto en la tenencia de perros). Por favor, marque uno:
£
£
£
£
£
£
De
$0
a
$ 2,699.00
De
$ 2,700.00
a
$ 6,799.00
De
$ 6,800.00
a
$ 11,599.00
De $ 11,600.00
a
$ 34,999.00
De $ 35,000.00
a
$ 84,999.00
ó
Mas
De $ 85,000.00
178
APPENDIX B
Modeling the effect of surgical sterilization and confinement on owned dog population size
using an agent-based computer simulation
179
B.1. Comparison of the impact of increasing the annual mortality rate for puppies from 5%
(A) to 10% (B) to 30% (C) for the mixed age sterilization interventions.
The top and bottom of the box are the 25th and 75th percentiles respectively, and the line inside the box is the median
dog population size after 20 years, based on 1000 simulations. The top whiskers are the minimum and maximum
projected population size, excluding outliers, which are represented in the figure by solid circles. In general, model
outcomes did not demonstrate drastic changes in the relative impact of the interventions under a wide range (5% 30%) of values for this parameter value.
100%
% Reduction in Population Size
25%
50%
75%
0%
A.
21
42
Number of Surgeries per Month
84
100%
% Reduction in Population Size
75%
50%
25%
0%
B.
21
42
Number of Surgeries per Month
84
21
42
Number of Surgeries per Month
84
100%
% Reduction in Population Size
75%
50%
25%
0%
C.
180
B.2. Comparison of the impact of increasing the annual mortality rate for young dogs from
10% (A) to 20% (B) to 30% (C) for the mixed age sterilization interventions.
The top and bottom of the box are the 25th and 75th percentiles respectively, and the line inside the box is the median
dog population size after 20 years, based on 1000 simulations. The top whiskers are the minimum and maximum
projected population size, excluding outliers, which are represented in the figure by solid circles. In general, model
outcomes did not demonstrate drastic changes in the relative impact of the interventions under a wide range (10% 30%) of values for this parameter value.
100%
% Reduction in Population Size
75%
50%
25%
0%
A.
21
42
Number of Surgeries per Month
84
100%
% Reduction in Population Size
75%
50%
25%
0%
B.
21
42
Number of Surgeries per Month
84
21
42
Number of Surgeries per Month
84
100%
% Reduction in Population Size
75%
50%
25%
0%
C.
181
B.3. Comparison of the impact of increasing the annual mortality rate for adult dogs from
1.5% (A) to 3% (B) to 7.5% (C) for the mixed age sterilization interventions.
The top and bottom of the box are the 25th and 75th percentiles respectively, and the line inside the box is the median
dog population size after 20 years, based on 1000 simulations. The top whiskers are the minimum and maximum
projected population size, excluding outliers, which are represented in the figure by solid circles. In general, model
outcomes did not demonstrate drastic changes in the relative impact of the interventions under a wide range (1.5% 7.5%) of values for this parameter value.
100%
% Reduction in Population Size
75%
50%
25%
0%
A.
21
42
Number or Surgeries per Month
84
21
42
Number of Surgeries per Month
84
21
42
Number of Surgeries per Month
84
100%
% Reduction in Population Size
75%
50%
25%
0%
B.
100%
% Reduction in Population Size
75%
50%
25%
0%
C.
182
B.4. Comparison of the impact of increasing the annual pregnancy rate from 10% (A) to
26% (B) to 40% (C) for the mixed age sterilization interventions.
The top and bottom of the box are the 25th and 75th percentiles respectively, and the line inside the box is the median
dog population size after 20 years, based on 1000 simulations. The top whiskers are the minimum and maximum
projected population size, excluding outliers, which are represented in the figure by solid circles. In general, model
outcomes did not demonstrate drastic changes in the relative impact of the interventions under a wide range (10% 40%) of values for this parameter value.
100%
% Reduction in Population Size
75%
50%
25%
0%
A.
21
42
Number of Surgeries per Month
84
100%
% Reduction in Population Size
75%
50%
25%
0%
B.
21
42
Number of Surgeries per Month
84
100%
% Reduction in Population Size
75%
50%
25%
0%
C.
21
42
Number of Surgeries per Month
84
183
B.5. Comparison of the impact of increasing the annual mortality rate for puppies from 5%
(A) to 10% (B) to 30% (C) for the young age sterilization interventions.
The top and bottom of the box are the 25th and 75th percentiles respectively, and the line inside the box is the
median dog population size after 20 years, based on 1000 simulations. The top whiskers are the minimum and
maximum projected population size, excluding outliers, which are represented in the figure by solid circles. In
general, model outcomes did not demonstrate drastic changes in the relative impact of the interventions under a wide
A
21
42
Number of surgeries per month
84
21
42
Number of surgeries per month
84
21
42
Number of surgeries per month
84
B
C
100%
% Reduction in Population Size
25%
50%
75%
0%
100%
% Reduction in Population Size
25%
50%
75%
0%
100%
% Reduction in Population Size
25%
50%
75%
0%
range (5% - 30%) of values for this parameter value.
184
B.6. Comparison of the impact of increasing the annual mortality rate for young dogs from
10% (A) to 20% (B) to 30% (C) for the young age sterilization interventions.
The top and bottom of the box are the 25th and 75th percentile respectively, and the line inside the box is the median
dog population size after 20 years, based on 1000 simulation runs. The top whiskers are the minimum and maximum
projected population size, excluding outliers, which are represented in the figure by solid circles. In general, model
outcomes did not demonstrate drastic changes in the relative impact of the interventions under a wide range (10% -
A
21
42
Number of surgeries per month
84
21
42
Number of surgeries per month
84
21
42
Number of surgeries per month
84
B
C
100%
% Reduction in Population Size
25%
50%
75%
0%
100%
% Reduction in Population Size
25%
50%
75%
0%
100%
% Reduction in Population Size
25%
50%
75%
0%
30%) of values for this parameter value.
185
B.7. Comparison of the impact of increasing the annual mortality rate for adult dogs from
1.5% (A) to 3% (B) to 7.5% (C) for the young age sterilization interventions.
The top and bottom of the box are the 25th and 75th percentile respectively, and the line inside the box is the median
dog population size after 20 years, based on 1000 simulation runs. The top whiskers are the minimum and maximum
projected population size, excluding outliers, which are represented in the figure by solid circles. In general, model
outcomes did not demonstrate drastic changes in the relative impact of the interventions under a wide range (1.5% -
A
21
42
Number of Surgeries per Month
84
21
42
Number of surgeries per month
84
21
42
Number of surgeries per month
84
B
C
100%
% Reduction in Population Size
25%
50%
75%
0%
100%
% Reduction in Population Size
25%
50%
75%
0%
100%
% Reduction in Population Size
25%
50%
75%
0%
7.5%) of values for this parameter value.
186
B.8. Comparison of the impact of increasing the annual pregnancy rate from 10% (A) to
26% (B) to 40% (C) for the young age sterilization interventions.
The top and bottom of the box are the 25th and 75th percentile respectively, and the line inside the box is the median
dog population size after 20 years, based on 1000 simulation runs. The top whiskers are the minimum and maximum
projected population size, excluding outliers, which are represented in the figure by solid circles. In general, model
outcomes did not demonstrate drastic changes in the relative impact of the interventions under a wide range (10% -
A
21
42
Number of surgeries per month
84
21
42
Number of surgeries per month
84
21
42
Number of surgeries per month
84
B
C
100%
% Reduction in Population Size
25%
50%
75%
0%
100%
% Reduction in Population Size
25%
50%
75%
0%
100%
% Reduction in Population Size
25%
50%
75%
0%
40%) of values for this parameter value.
187