COSTA RICA FOREST RESEARCH
PROGRAMME
CRF
Carate, Osa Peninsula, Costa Rica
CRF Phase 161 Science Report
1 January 2016 – 31 March 2016
Jenna Griffits, Charlotte Watteyn, Berglind Karlsdottir, Alex McCafferty, Aslheigh Arton,
Alistair Ross, Joe Wilcox
CRF161
Griffiths J, Watteyn C., Karlsdóttir B., McCafferty A., Arton A., Ross A., Wilcox J.
Staff Members
Jenna Griffiths (JG)
Research and Operations Manager (ROM)
Charlotte Watteyn(CW)
Principal Investigator (PI)
Berglind Karlsdottir (BK)
Assistant Research Officer (ARO)
Alex McCaffety (AC)
Assistant Research Officer (ARO)
Ashleigh Arton (AA)
Assistant Research Officer (ARO)
Alistair Ross (AR)
Field Communication Officer (FCO)
Joe Wilcox (JW)
Conservation Apprentice (CA)
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Content
1.
2.
3.
Introduction ................................................................................................. 5
1.1
Natural history of Costa Rica and its wildlife conservation .................... 5
1.2
Osa Peninsula ....................................................................................... 6
1.3
Aims and Objectives of Frontier CRF .................................................... 8
Training ..................................................................................................... 10
2.1
Briefing Sessions ................................................................................ 10
2.2
Science Lectures ................................................................................. 10
2.3
Field Training ...................................................................................... 11
2.4
BTECs, CoPEs and TEFLs during phase CRF161. ............................ 11
Research Work Programme ...................................................................... 12
3.1
Survey Areas ....................................................................................... 12
3.2
Projects .............................................................................................. 13
3.2.1 Estimating the Population Density of the Four Primate Species
Coexisting ..................................................................................................... 13
Introduction ................................................................................................... 13
Material and Methods .................................................................................. 13
Results .......................................................................................................... 15
Discussion .................................................................................................... 15
3.2.2 Poison dart frog study .......................................................................... 15
Introduction ................................................................................................... 15
Material & Methods ....................................................................................... 16
Results .......................................................................................................... 19
Discussion .................................................................................................... 20
3.2.3 Mammal track study along Rio Carate, Osa Peninsula ........................ 23
Introduction ................................................................................................... 23
Material & Methods ....................................................................................... 24
Results .......................................................................................................... 26
Discussion .................................................................................................... 30
3.2.4 Turtle predation study along Carate and Leona beach, Osa Peninsula.
...................................................................................................................... 32
Introduction ................................................................................................... 32
Material and Methods ................................................................................... 33
Results .......................................................................................................... 35
Discussion .................................................................................................... 35
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3.2.5 Birds of Carate lagoon, a study on the species richness and abundance
...................................................................................................................... 36
Introduction ................................................................................................... 36
Material and methods ................................................................................... 37
Results .......................................................................................................... 38
Discussion .................................................................................................... 41
3.2.6 Bird species richness and abundance in primary, secondary and
degraded forest............................................................................................. 43
Introduction ................................................................................................... 43
Material and Methods ................................................................................... 45
Results .......................................................................................................... 48
Discussion .................................................................................................... 48
References ................................................................................................... 49
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1. Introduction
1.1
Natural history of Costa Rica and its wildlife conservation
Costa Rica, located between Nicaragua and Panama, is one of the seven Central American
countries and covers an area of 51.100 km2. It is surrounded by the Pacific on the west and the
Caribbean on the east, creating a coast line of 1103 km and 255 km respectively. Even though
this small country covers only 0.01 percent of the earth’s surface, it contains >4% of the
world’s biodiversity, including around 12,000 plant species, 1,239 butterfly species, 838 bird
species, 440 reptile and amphibian species, and 232 mammal species (Sánchez-Azofeifa et al.,
2002; IUCN, 2006; World Resources Institute, 2006; National Biodiversity Institute, 2007). The
high species richness has been attributed to two main factors; its geographical location and
climatic conditions. The fact that Costa Rica is situated between North and South America
means it can serve as a species corridor between these two continents. Furthermore, it lies
halfway between the Tropic of Cancer and the equator, leading to an annual average
temperature of 27 °C, with very little fluctuations throughout the year. Therefore, the seasons
in this area are defined by precipitation, not temperature, resulting in a distinct dry and wet
season. The dry season starts around November/December and continues through April/May,
after which the rainy season begins. The southern Pacific lowlands receive a particularly high
degree of average annual rainfall (about 7,300 mm) (Baker, 2012). Although more than onefifth of Costa Rica is protected, further action must be taken in order to raise, or at least
sustain the current level of biodiversity (World Resources Institute, 2006).
Costa Rica is one of the world’s leading countries in environmental sustainability and
conservation (Fagan et al., 2013), however, this has not always been the case. Like many other
countries throughout the world, Costa Rica has been the site of extensive deforestation over
the past few centuries. Up until the 1960s, activities such as logging and hunting seriously
threatened the biodiversity in this region, resulting in over half of the country’s forests being
cut down and many species being driven to the verge of extinction (Henderson, 2002). The
poaching of turtles for the fatty calipee and collection of turtle eggs for example, has severely
depleted populations of endangered black turtles (Chelonia mydas) and vulnerable olive ridley
turtles (Lepidochelys olivacea) that use Costa Rica’s coastlines as nesting sites. Similarly, the
hunting of Costa Rica’s wild cat species, peccaries and tapirs for their meat, skins and other
body parts, has significantly reduced wild populations. Since the 1960s, some of these issues
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have been controlled through the implementation of several reforestation programs,
legislation, education and the creation of protected areas, now representing almost 27% of the
country’s surface area (The World Bank Group, 2015). Costa Rican law currently protects 166
species from being hunted, captured and traded, yet illegal hunting still occurs, including in
protected areas (Baker, 2012). Deforestation and habitat fragmentation outside of the
country’s protected areas and national parks is still a significant problem due to expanding
human populations and related increases in economic pressure. Additionally, the projected
impacts of climate change are also likely to have significant adverse effects on Costa Rican
biodiversity (Baker, 2012). Due to the high levels of biodiversity and multiple threats placed on
Costa Rica it is important to conduct research to determine the health of the ecosystem and its
species. Massive deforestation and the resulting biodiversity crisis have already increased
awareness and interest in conservation of tropical habitats worldwide (Wilson, 1992), but the
real practice requires a basic understanding of the native fauna and flora; and since tropical
forests are not single, homogeneous, biotic formations (Gentry, 1990), the biodiversity of
these areas must be understood on a local, as well as regional, level.
1.2
Osa Peninsula
The Osa Peninsula is located in the southwest of Costa Rica and covers an area of 1093 km²
(Henderson, 2002). The peninsula contains the last remnants of tropical broadleaved
evergreen lowland rainforest on the Central American Pacific slope (Kappelle et al. 2002) and
has a very high species richness of about fifty percent of Costa Rica’s biodiversity.
Furthermore, this area inhabits several endemic species such as the Cherrie’s Tanager
(Ramphocelus costaricensis), the Red-backed squirrel monkey (Saimiri oerstedii)) and the Golfo
Dulce poison dart frog (Phyllobates vittatus). Since these and more species are only found in
this area, it makes the Osa Peninsula the ideal location for conservation research (Larsen &
Toft 2010).
Three main forest types can be found in the Osa Peninsula; Tropical Wet, Premontane Wet and
Tropical Moist forest, with elevations ranging between 200 and 760 m (Santchez-Azofeifa et
al., 2002). The variation in topography leads to a highly variable climate, with an average
annual rainfall of 5500 mm, a mean temperature of around 27 °C and humidity levels almost
never dropping below 90% (Cleveland et al, 2010). There are about 12,000 people living in the
Osa Peninsula, mainly settled in small and scattered villages. The most important sources of
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income in this region are agriculture (rice, bananas, beans and corn), livestock (cattle), gold
mining, logging and, more recently, the expanding eco-tourism industry (Carrillo et al., 2000).
The human population is increasing at a rate of 2.6% annually, which is incredibly high
compared to 1.3% in the rest of the country and 1.14% globally (Sánchez-Azofeifa et al., 2001).
As a result of the growing popularity of ecotourism, there has been a rise in the number of
hospitality business along the road, from Puerto Jimenez to Carate, since the 1990s (Minca and
Linda, 2002). This has caused growing concern for the sustainability of the region’s
environmental resource demands (Sánchez-Azofeifa et al., 2001).
The Frontier’s Costa Rica Forest Research (CRF) programme began in July 2009 in collaboration
with the local non-governmental organisation, Osa Conservation, based at the Piro site (N
08°23.826, W 083°20.564) in the southeast of the Osa Peninsula. In October 2015, Frontier
moved to Carate, located in the southwest of the Osa Peninsula. The site is a prime location for
carrying out both forest and shoreline surveys as there is relatively easy access to both the
primary and secondary forest, as well as pristine beach habitat. The long term objectives of the
project are to provide information on the dispersal and diversity of faunal communities in the
Golfo Duche Forest Reserve, with the aim of increasing protections and connectivity in the
area, whilst also investigating the effects of climate change, deforestation and other
anthropogenic impacts on the terrestrial communities of Costa. There are six core faunal study
groups within CRF; primates, sea turtles, wild cats and other mammals, Neotropical otters,
amphibians and reptiles and birds.
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Figure 1. Map of the Osa Peninsula, showing Carate, our area of study http://www.vivacostarica.com/costa-ricamaps/costa-rica-maps-southern-pacific.html.
1.3
Aims and Objectives of Frontier CRF
Under the umbrella of the research program, the specific aims and objectives of Frontier CRF
are:
1. To estimate the population density, distribution and feeding preferences of the four
primate species present in Carate, Osa Peninsula, Costa Rica; and compare these
among the different habitat types present in this area.
2. To estimate the population density and distribution of Poison dart frogs in Carate,
more specifically in Leona Loop, using a mark-recapture method; and to see how
environmental changes affects the Poison dart frog population.
3. To assess mammal species richness and abundance along Rio Carate by searching for
natural tracks in and near the riverbed.
4. To assess nest success and turtle nest predation by conducting morning and night
turtle patrols along two beaches, Playa Carate and Playa Leona.
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5. To determine bird species richness and abundance in and around the lagoon of
pejeperrito in Carate; and to see how changes in environmental variables affect the
presence of these species.
6. To compare the bird species richness and abundance between primary, secondary and
degraded forests, by performing point counts along the different trails, focusing on 44
forest bird species selected on several criteria, such as endemism, IUCN status,
ecological function and migratory features.
7. *To gather information about the amphibian and reptile species richness in the
primary, secondary and degraded forests of Carate, Osa Peninsula, Costa Rica.
8. *To study to otter populations present along the rivers, streams and lagoons in Carate.
*The points in italic are the studies that are still in their initial phases and will be included
during
the
next
science
report
(phase
9
2;
April
–
June
2016).
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2. Training
The volunteer Research Assistants (RAs) and newly appointed staff members receive a number of
briefing sessions on arrival (Table 1), followed by regular science lectures and field training (Table 2)
throughout their deployments. The CRF research program also supports candidates completing the
BTEC Advanced Certificate, Advanced Diploma in Tropical Habitat Conservation, the Certificate of
Personal Effectiveness (CoPE) and the Teach English as a Foreign or second Language (TEFL) (Table 4).
2.1
Briefing Sessions
All the people newly arriving to CRF get an introduction towards the aims of the research
programme, the methodologies used and the research output of the individual projects.
Furthermore, they get an update on the achievements of CRF through a general Science
presentation, this is an introduction to the Frontier Costa Rica Forest Research Programme in Carate.
Additionally, all volunteers and staff are given a health, safety and medical briefing, of which they are
tested on before participating in any field activity. Volunteers undertaking any kind of the previous
mentioned qualification courses are given an introductory briefing before they begin the
assessments.
Table 1. Briefing sessions conducted during Phase CRF151
Briefing Session
Presenter
Introduction to the Frontier Costa Rica Forest Research Programme
JG, CW
Health and Safety Briefing and Test
CW, BK, AA, JW
Medical Briefing and Test
CW, BK, AA, JW
Introduction to the BTEC, CoPE & TEFL Qualifications
JG, CW
Introduction to Surveying and Monitoring
ALL
Camp Life and Duties
JG, CW
2.2
Science Lectures
A broad program of science lectures is offered at CRF, providing information and training the
different aspects of research going on in our study area. Lectures are presented using PowerPoint
and give a better understanding about the biology and ecology of the studied species. Furthermore,
they give an insight in the methods and data analysis used by CRF and considerations made when
planning research projects.
Lectures are scheduled with the following objectives:

To allow every volunteer and member of staff to attend each presentation at least once
during deployment, regardless of length of stay.

To meet the time requirements for BTEC assessments.
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
To avoid conflict with other activities, maximizing attendance.

To provide detailed training on specific software and applications used in conservation, such
as GPS.
Attendance of lectures is compulsory.
Table 2. Science lectures delivered during Phase CRF161.
Science Lecture
Presenter
Primates
JW, AC
Terrestrial birds
CW
Lagoon birds
BK
Turtle patrol survey
JG
Mammal tracks and GPS workshop
JG
Climate change
ALL
2.3
Field Training
All volunteers and newly appointed staff members receive field training. Training is hands-on and
provides an opportunity to become familiar with the field equipment used during surveys. These
sessions are hold before starting every survey, to inform volunteers and new staff members about
the way the survey is carried out and to assure accurate data collection. Both in the field and on
camp site, various identification books are present to teach how to identify flora and fauna species.
2.4
BTECs, CoPEs and TEFLs during phase CRF161.
Frontier offers volunteer Research Assistants an opportunity to gain internationally recognised
qualifications based around teamwork, survey techniques, environmental conservation and effective
communication of results. The BTEC in Tropical Habitat Conservation can be done in a four week
program (Advanced Certificate) or a ten week program (Advanced Diploma). Table 4 gives an
overview of the BTECs carried out during this phase.
Table 3. BTECs, CoPEs and TEFLs during phase CRF 161.
Name
BTEC Title and Type
Mentor
Aneira Williams
Mammal species richness and abundance, a comparison between two
trails Rio Carate and Atalea Loop.
Goal: Aneira wanted to carry out a BTEC in order to start a Master’s
degree in Conservation science.
CoPE Title and Type
JG, CW, AA
General CoPE certificate
Goal: Nicole wanted to carry out a CoPE in order to get into the army
as a logistic officer.
JG, CW
Name
Nicole Huggins
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3. Research Work Programme
3.1
Survey Areas
All the fieldwork is carried out in Carate, located in the southwest of the Osa Peninsula. The research
in this area has just began in November 2015. The landscape is heterogeneous, composed of lowland
moist primary, secondary and coastal forest, and disturbed forest. Dominant tree species include;
Ficus insipida, Ceiba pentandra, Attalea butyracea, Carapa guianensis, Castilla tunu, Spondias
mombin, Hyeronima alchorneoides, Chimarrhis latifolia, Fruta dorada, Caryocar costaricense, Ocotea
insularis, Pouteria torta, and Inga allenii. Mean annual rainfall and temperature for the area is 5,0006,000 mm and 26-28 °C respectively; the dry season extends from the end of December until March.
Different trails have been selected, including the different types of habitat and with different degrees
of usage and disturbance (table 1). These trails are used as survey transects for our eight different
projects. Most of the trails are narrow and machete-cut. We are still not fully sure about the exact
habitat types present in our trails, for example, it is highly possible that Luna ridge contains a mix of
primary and secondary forest. In order to assess this in more depth we are currently undertaking GIS
work and also require in-depth habitat studies, perhaps with the help of drones to get more
knowledge about all the different habitat types present in Carate and surroundings.
Table 4. Current trails used for the research carried out in Carate S coordinates of the start and the end of the trail, as well
as the length (km).
Trail Name (code)
Transect
Length (km)
Disturbed forest
Attalea Loop
Road
Beach Trail
Secondary forest
Shady Lane
Leona Loop
Rio Carate
Primary forest
Leona Ridge
Luna Ridge
GPS
Coordinates
START trail
GPS
Coordinates
END trail
08º26'11.14 N
83º26'16.99 W
08º26'28.37 N
83º26'25.73 W
08º26'36.69 N
83º27'49.54 W
08º26'29.60 N
83º29'02.37 W
08º26'28.11 N
83º27'16.33 W
08º26'50.30 N
83º29'02.37 W
08º26'56.09 N
83º29'04.37 W
08º26'33.01 N
83º27'23.26 W
08º26'56.39
N83º29'05.16 W
08º27'37.30
N83º27'48.69 W
08º26'48.19 N
83º28'52.97 W
08º26'29.63 N
83º27'16.62 W
08º26'54.51
N83º29'05.16 W
08º26'28.54 N
83º26'56.86 W
We are very close to the Pacific ocean, and use the two beaches, Playa Carate and Playa Leona for
our turtle patrols. There is also the river Rio Carate passing through our survey areas, bordering the
National park of Corcovado, and has an important function in providing water and food for animals
when they move out of the park.
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3.2 Projects
3.2.1 Estimating the Population Density of the Four Primate Species Coexisting
Introduction
Throughout Costa Rica, four different primate species can be found; the Central American squirrel
monkey (Saimiri oerstedii), the mantled howler monkey (Alouatta palliata), the geoffroy’s spider
monkey (Ateles geoffroyi) and the white-faced capuchin (Cebus capucinus). The Osa Peninsula is the
only part of Costa Rica where these four new world primate species occur together, making this place
a very interesting area for study (Carrillo et al., 2000). Primates are predominantly frugivorous,
therefore, they have an important ecosystem function as seed dispersers, making them vital for
maintaining the plant diversity within the forest (Julliot, 1997; Garber et al., 2006). Generally,
primate species are highly sensitive to land conversion for agricultural purposes and development,
clear cutting, selective logging, hunting and the pet trade (Cropp and Boinski, 2000). In Costa Rica,
primates are mainly threatened by increased rates and amounts of forest loss and fragmentation,
and infrastructural changes for the country's booming tourism industry. In Panama, they have fared
even worse since deforestation has been extensive and unregulated (Boinski & Sirot 1997; Boinski et
al. 1998). The development of agribusinesses for oil palm and banana plantations is a serious
component of habitat destruction and fragmentation. Logging roads, clearings for telephone and
electric power lines, or other practices leading to forest fragmentation restrict populations to smaller
forest areas, decreasing their ability to find food during times of the year when food abundance is
lowest (e.g. dry season) and leading to declines of genetic diversity, which in turn affects the
population health and stability (Boinski et al. 1998).
Since October 2016 Frontier CRF has been surveying the presence of the four primate species in
Carate. The overall research aim is to gain more knowledge about the distribution of the four primate
species in this area of the Golfo Duche Reserve. By comparing the richness and abundance of primate
species between the different habitat types, we can gain more information regarding management
and policy decisions on a local level. Until now, density estimates are lacking for the Central
American squirrel monkey and the white-faced capuchin, which makes them key to survey, however,
focus is also places on the red listed spider monkey and squirrel monkey.
Material and Methods
The Central American squirrel monkey (Saimiri oerstedii) is one of the five species of squirrel
monkeys. Their status on the IUCN list is Vulnerable, with decreasing populations (IUCN, 2008). The
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main threats are habitat loss due to logging and agriculture. They inhabit the lowland rainforests of
Pacific Costa Rica towards Western Panama. They are arboreal and diurnal species, depending on a
diet of insects, leaves, fruits, barks, flowers and nectar, and foraging in the low and middle levels of
primary and secondary forests. Group sizes range from 20 to 75 individuals that are travelling
between 2.5 and 4.2 km per day (IUCN, 2008). The white-headed capuchin (Cebus capucinus), also
known as the white-faced or white-throated capuchin, has a very important ecological function
within the forest ecosystem by dispersing pollen. They are Least Concern on the IUCN list but their
main threats include tree logging and clear-cutting because these activities drastically reduce suitable
habitats. Other threats include the capturing for the pet trade and hunting for their meat. Like the
squirrel monkeys, the capuchins are diurnal and arboreal species with a diet of mainly fruits and
insects. They range from Honduras all the way down to Ecuador and are highly adaptive species,
meaning they can occupy various habitats, but usually occur in tropical evergreen and dry deciduous
forests. Their group size ranges from 4-40 individuals, with a mean average of 16 and they travel on
average 2 km a day (IUCN, 2008). The Golden mantled howler monkey (Alouatta palliata) are found
in Costa Rica, Nicaragua, Panama and Guatemala, mostly in the older areas of evergreen primary
forest as well as secondary and semi-deciduous forest. They have an important function as seed
dispersers and germinators and their dung is an important food source for several dung beetle
species. Their status on the IUCN list is Least concern (IUCN, 2008). They are diurnal, arboreal species
with a diet that mainly consists of leaves, giving them low amounts of energy which makes them
resting during most of the day. Their main threats are forest destruction and fragmentation. The
group size ranges from 10-20 individuals, but can reach up to 40 individuals. The males are
characterized by a very obvious white scrotum when they reach sexual maturity and have an enlarge
hyoid bone which allows them to create a loud howling noise, usually displayed at dawn and dusk
(IUCN, 2008). The Geoffroy’s spider monkey (Ateles geoffroyi) is native to Costa Rica and Panama and
is currently Endangered with a decreasing population (IUCN, 2008). They are diurnal and arboreal
species, mainly inhabiting the upper layers of the forest, and have a diet of fruits, leaves and
sometimes insects, seeds, barks and flowers. Their threats are habitat loss and hunting for their meat
and the pet trade. The group size ranges from 20-40 individuals that are living in a fission-fussion
society, meaning that they split into subgroups during the day and congregate again during the night
(IUCN, 2008).
Data is collected by walking six different trails (Beach trail, Road, Attalea loop, Luna ridge, Leona
loop, Shady lane) and conducting total counts of all the primates encountered. The surveys started
between 05.30 and 06.00 am, to cover peak primate activity and thus increasing detection
probability. A minimum of three observers are walking at a constant speed of 2 km/h, including
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regular stops every 100m as recommended by Peres (1999). The six trails are divided into three main
habitat types; primary (Luna ridge, Leona loop), secondary (Beach trail, Shady lane) and degraded
(Road, Attalea loop) forests. Each trail is walked in one way, and this not more than once a week. The
surveys are done in fair weather because of reduced detection probability in adverse weather
conditions. Since phase one is in the middle of the dry season, we didn’t have problems with
cancelling surveys because of adverse weather conditions. When encountering a monkey troop, an
observation time of maximum 30 minutes was set. This gives us enough time to assure a reliable
count of all the individuals without disturbing them for too much time (Pruetz & Leasor 2003). All
individuals seen at the same time and exhibiting the same general behaviour (e.g., resting, moving or
foraging) were considered to be part of the same group (Chapman et al., 1995). Where possible,
secondary data on group composition (i.e. gender and age group; adult, juvenile, infant) was also
recorded. Furthermore, the behaviour (e.g. resting, moving or foraging) upon encounter, the
duration of observation, the perpendicular distance from the trail to the geometric centre of the
group at first sighting, height of the group in the tree and direction of travelling was noted. This study
was non-invasive and according to the legal requirements of Costa Rica (Costa Rican Government
Decree 31514-MINAE). Any kind of abnormal or aggressive behaviour towards the observers by
individual primates was responded to by moving on as quickly as possible.
Results
In progress. We recently changed the methods for primates. Instead of focusing on their home
ranges (see science reports of 2015), we want to start a general study on their distribution and
compare the richness and abundance among the different types of habitat. Therefore, we first need
to carry out more research about the best suitable methods, for example, the use of line transects,
and a laser range finder to make better estimates about the distances of the primate groups from the
observation point on the trail, etc. This will involve a more in-depth literature study during the next
phase in which we hope to implement the new methods.
Discussion
In progress.
3.2.2 Poison dart frog study
Introduction
Worldwide, human activities are having negative effects on natural environments and the species
they inhabit. Since most amphibian species have small geographical ranges, they are likely to be the
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major group at risk. Thanks to the now-general understanding that most of the amphibian species
are at risk, they have received more attention during the last two decades (Stuart et al., 2004). About
one-third of the 6,300 known species are currently threatened with extinction due to a combination
of habitat destruction and degradation, the spread of virulent diseases, pollution, climate change and
the pet trade (Wake & Vredenburg, 2008; ZSL, 2016). They are highly sensitive to environmental
changes, leading to population decreases and even extinctions (ZSL, 2016).
This study focuses on the green and black poison dart frog (Dendrobatus auratus), which is one of
more than 200 poison dart frog species. Because of their toxicity, poison dart frogs have only one
predator; Leimadophis epinephelus, a snake species that has built up resistance over time. The bigger
and more widespread threat for poison dart frogs is the logging and clearing of the rainforests,
causing a decline and dry-out of their natural habitat. Air and water pollutants also have tremendous
effects on the growth and reproduction of the frogs, by polluting the environment in which they live,
reducing their food supply, and negatively affecting their immune system. Furthermore, like other
amphibian species, poison dart frogs are threatened by the fungal disease Chytridiomycosis. This
fungus is possibly causing the biggest loss of biodiversity recorded in history. The bright colour of the
poison dart frogs strikes the attention of having them as pets, leading to the illegal catching and
worldwide trading of poison dart frogs. Climate change is a more recent threat, whereby
temperature and sea level rises, droughts and extreme weather events are affecting their time of
breeding, skin moisture and egg survival (reference). Many poison dart frog species are decreasing in
population sizes, and some of them are now classified as Endangered (IUCN, 2008). The aim of this
study is to start long-term research on the population size and distribution of D. auratus in an
evergreen primary rainforest, located on a south facing slope near the Pacific coast adjacent to La
Leona beach, Carate, Osa peninsula, Costa Rica. By using a mark-recapture method based on
photographs of the unique pattern, we want to get an estimate of the population size of D. auratus
present in this area. Furthermore, we want to examine how environmental parameters, such as
habitat characteristics, weather, light intensity, soil moisture and temperature, influence the
presence of this species of poison dart frog.
Material & Methods
The species under study is Dendrobates auratus (Dendrobatidae family), better known as the green
and black poison dart frog. D. auratus belongs to the Dendrobatidae family, which is one of the two
poison dart frog families. Both Dendrobatidae and Aromobatidae families are native to the
rainforests of Central and South America. About a quarter of the more than 200 poison dart frog
species are listed as threatened or critically endangered. The green poison dart frog is listed as Least
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concern on the IUCN list (IUCN 2016). Adults are marked with contrasting green coloured bands and
spots on a black background, and are usually about 25-39 mm and 27-42 mm in length for
respectively males and females (IUCN 2016). They can reach the age of eight years, but is much lower
in the wild (Leenders, 2001)They are arboreal and terrestrial diurnal frog species, meaning they are
actively foraging during the day by moving in hops on the ground or in large buttressed trees (Guyer
& Donnelly, 2005). They are native to the humid lowland and submontane forests of Costa Rica,
Panama, Nicaragua and Columbia (Leenders, 2001; Savage, 2002; Caldwell & Summers, 2003; Guyer
& Donnelly, 2005). However, they have been introduced in similar habitat types in e.g. Hawaii, to
control non-native insect pests. Poison dart frogs produce powerful skin alkaloids, which are used for
defence purposes, by consuming toxic ants and store these alkaloids in their skin. The brighter the
coloration, the higher the amount of alkaloids present in the skin. Females actively compete for
males and lay about four to six eggs in the nest made by the chosen male (Savage, 2002; Guyer &
Donnelly, 2005). Males can mate with up to six females and show a high degree of paternal care,
taking care for the offspring of different females simultaneously (Savage, 2002; Caldwell & Summers,
2003). After oviposition upon leaf-litter, the male guards and takes care of the clutch by regular
visits, removing fungus and rotating the eggs (Silverston, 1975; Schafer, 1981; Heselhaus, 1992).
Upon hatching, the males carry the tadpoles towards stagnant water bodies in a tree hole, the leaf
axil of a bromeliad, or a small ground pool (van Wijngaarden, 1990).
The fieldwork is carried out on the Leona Loop trail, which is located in primary lowland rainforest
habitat (Figure …). The reason for studying this area evolves from a previous BTEC, focusing on the
home range of the green and black poison dart frog in a habitat of which it was sure to encounter a
decent amount of individuals. The trail was initially divided into 11 sectors in order to get an idea of
their home ranges. We are now carrying on this study, but focusing on the population density on
Leona Loop. During the survey, two observers are walking in front and spot all the frog individuals on
the path as well as one meter alongside the path, in the leaf litter, on tree logs and in the trees. Two
other observers in the back are slightly poking the leaf litter with a stick, again up to one meter along
the path to look for individuals that might be missed out by the two persons in the front. Since this is
a mark-recapture study, all individuals seen along the trail are ‘marked’ by taking a picture of the
back and legs. Using invasive techniques for marking anurans has been strongly debated during the
last years based on ethics, public opinion, infection risk and impacts on behaviour and survival of the
marked individuals. Photographing the distinguishable markings that remain constant through time is
a possible alternative for identifying the different individuals present in area (Kenyon et al., 2009).
The pictures have to be taken from above to be sure the back pattern is clearly visible. Poison dart
frogs distinguish themselves from one another by the green pattern on their back and legs, that
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serves as a sort of fingerprint. Furthermore, each time an individual is spotted, information about
canopy cover, percentage of shade and habitat in which they are found are written down, as well as
the weather of the previous and present day. Back home, the pictures are compared with previous
ones to see if we have new are recaptured frog individuals. The study was non-invasive and
according to the legal requirements of Costa Rica (Costa Rican Government Decree 31514-
MINAE). The owner of La Leona Lodge, Adrian Morales Polanco, gave us the permission to start a
study on his land. Field staff just need to introduce the new volunteers the first time they come on
his land. Since we are not using camera traps or physically catching the frogs, we don’t need any kind
of government permits.
Figure 2. A map of the trail, used for the poison dart frog study, with the division into the different sectors.
We use the program MARK, a Windows or XP program providing parameter estimates from marked
animals when they are re-encountered at a later time. Usually, re-encounters can be from dead
recoveries (e.g. the animal is harvested), live recaptures (e.g. the animal is re-trapped or re-sighted),
radio tracking, or from some combinations of these sources of re-encounters. In our case, the
individuals are not physically captured and marked since amphibians are very sensitive towards
manual handlings, and our frog species is highly poisonous. Instead, pictures of the back and legs are
taken and identified back on camp to check if we have a new individual or a re-encounter. The time
intervals between re-encounters are about one week (time-unit). The basic input to the program
MARK is the encounter history for each frog individual. In this way, we are able to estimate the
encounter probability (p) and the survival rate of the population (phi). The population density is
estimated by using the formula:
N=(
) / R; with
(1)
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-
N
k
C
M
R
= estimated population density
= amount of surveys (1 to 16)
= number of captures
= cumulative number of unmarked captures
= total number of recaptures
Results
The survival rate (Phi) is estimated at 0.9154318, which is very high (Phi lays between 0 and 1). This
means that the individuals within our population have a chance of 91.5% to survive from one sample
(survey) to the other. The encounter probability (p) is changing over the surveys. In the beginning,
the encounter probability is quite high, varying between 0.3345101 and 0.5258023. From survey 8
onwards, the encounter probability decreases and fluctuates around 0.20. From this we can say that
during the first couple of surveys we encountered more of the same frogs, whereas during the last
surveys we recaptured less and saw more new frog individuals. Table … gives an overview of the Phi
and p values, with their standard errors and lower/upper 95% confidence intervals.
Table 5: Overview of the parameter estimates Phi and p, and their standard errors and lower/upper 95% confidence
interval.
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Encounter probability
Encounter probability (p) (%)
60
50
40
30
20
10
0
0
2
4
6
8
10
12
14
16
Survey
Figure 3. Graph showing the frog encounter probability throughout the surveys.
Based on the formula (1) described in the Materials and Methods section, we could estimate the
population density of green and black poison dart frogs in Leona Loop in Excel. So far, the density of
the population is estimated at 83.65625 individuals.
Discussion
During this first phase of the poison dart frog study in Leona Loop, we can say that 1) there is a very
high survival rate within the population, 2) the encounter probability changes over time, with more
of the same frog individuals recaptured during the first surveys than later on, and 3) the population
density so far is estimated at 83 individuals.
The high survival rate can be explained by the fact that the population in Leona Loop is very healthy
at the moment and that the environmental conditions are very positive in and around Leona Loop.
The fact that the poison dart frogs do not have natural enemies in this area also explains their high
level of survival. As mentioned before, the green and black poison dart frog has only one natural
enemy, Leimadophis epinephelus, who is not present here. Furthermore, the high survival rate also
indicates that our presence (noise and disturbance of the leaf litter) during the surveys does not give
a big amount of stress to the frogs and does not negatively impact the frog population. The fact that
we encounter more of the same frog individuals during the first surveys then at the end, might be
due to our survey effort. During the whole period of phase one, there was a change in staff working
on the project. Some people are better in spotting frogs then others, and it also takes some time to
learn where to look for the frogs. This can explain the higher amount of new frog individuals at the
end of the period. Observers (mainly the long-term field staff members) gained more skills in finding
the frogs compared with the time when they first arrived. Besides the change in encountering frogs
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throughout the surveys carried out during phase one, there can also be a change during the survey
itself; with observational concentration being very high at the start of the survey and lowering down
by the end, causing a drop in frog encountering. During the next phase we will start to alter carrying
out surveys starting at sector one, and starting at sector 10. In this way we will be able to compare
where most of the frogs or found and see if there actually is an effect of the observers’ concentration
on the amount of encountered frogs. It is also possible that the frogs changed their behaviour upon
changes in environmental conditions (reference). They could be moving to other areas, or higher up
in the trees where it is less obvious to encounter them. The fact that we saw more new individuals by
the end, can be explained by the first rains coming in, so frogs coming back to the area, or juveniles
that are adults now and coming down from the trees (reference).
The population density so far is estimated around 83 frog individuals, which is quite low for
amphibians (reference). We are now during the dry season, and the dryer environment could have
stimulated some frogs to withdraw beneath damp leaf litter, thus reducing the number of exposed,
observable frogs and the density estimates recorded during this phase of the project. Previous
studies have shown that poison dart frogs use water from small pools of rainwater among the leaf
litter (Vences et al., 2000; Jowers & Downie, 2005). There was almost no rain during the last three
months, which can explain our low population density estimate. Furthermore, the fact that
Dendrobatids lay their eggs on the land and carry their larvae to small pools of water in the folds of
leaves, supports the random and independent distribution of poison dart frogs in the area (Miller,
2007). Poison dart frogs have been randomly observed in Carate, along the beach trail andshady
lane, etc. This is interesting regarding further research about the poison dart frogs in this area, in
which we might not only focus on Leona loop, but include other trails as well.
Studies have shown that D. auratus has bimodal peaks of activity, around 7am and 5pm (Jaeger &
Hailman, 1981; Graves, 1999; Miller, 2007). The high activity during the early morning is a product of
multiple factors. Environmental conditions are more favourable thanks to higher ground moisture
levels from unevaporated rainfall during the night, lower light and temperature levels, leading to
lower rates of evaporative water loss. Furthermore, during this time of the day, arthropod activity
might be higher, allowing frogs to forage more easily (Basset et al., 2001). Taking this into account,
we will commence our study of the poison dart frogs 30 minutes earlier (at 7am instead of 7.30am),
and carry out surveys late in the afternoon as well. However, this has to be logistically possible (5pm
is late to start a survey, and it is possibly too dark to return from Leona to Carate after the survey).
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To account for the impacts of abiotic factors on frog sighting frequencies, the proximity to water, as
well as correlations with rainfall (humidity), air and ground temperature, light intensity need to be
considered. Especially rainfall and time of the day have both been identified as influencital factors,
with some poison dart frogs occurring in larger quantities in the presence of rain because of the
higher humidity percentage (Graves, 1999). We are currently looking at placing some HOBO’s in
Leona loop, to start measuring these environmental parameters in order to gain more knowledge
about how the environment affects the presence of the poison dart frogs in this area.
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3.2.3 Mammal track study along Rio Carate, Osa Peninsula
Introduction
In general, protected areas are the backbone of conservation and are supposed to safeguard the
species inside the area. However, many protected areas don’t function in the way they should (e.g.
Caro & Scholte, 2007; Russel & Cuthill, 2009; Craigie et al., 2010). Effective protection to maintain
healthy species richness and abundance can vary with the location and size of the area. Furthermore,
abiotic and biotic as well as indirect and direct human activities occurring close to the borders of the
reserve, such as firewood collection, cattle grazing, bush fires, fishing and hunting, are affecting all
the organisms living in or crossing the periphery of the reserve (Laurance, 2010). With increasing
human disturbance, mammals often move to the central parts of protected areas while areas closer
to the park boundaries may be less attractive due to the negative effects of human activities along
the edges. Despite the fact that these so-called edge effects can have big consequences regarding
conservation issues (e.g. Primack, 2010), this topic has received little attention. Most of the studies
have been focusing on large carnivore species (e.g. Revilla et al., 2001; Slotow & Hunter, 2010),
showing that their large individual home ranges are extending the boundaries of the decreasing
reserve areas, leading to a movement outside the reserves via buffer zones. However, the threats
outside the reserves, block these species to move out of the reserve. Instead, they often have to
move back towards the centre, leading to population declines due to habitat and food competition.
Despite protective legislation, these kind of human-wildlife conflicts are common throughout Central
and South America (Zimmermann et al. 2005), as natural habitats are still being converted for
agricultural purposes and resource extraction, and poaching activities are still present along the
reserve borders (Cavalcanti & Gese 2009).
Estimating the distribution and abundance of mammals is not that easy. Especially in the case of the
Osa Peninsula, where big mammals are extending their home ranges from Corcovado National Park
towards other areas within the Osa Peninsula. This makes it even more vital to conserve and manage
these areas and the biological corridors that connects them. Information on the distribution is also
vital for the introduction of education and awareness initiatives, with the aim of preventing humanwildlife conflict that threatens mammal populations and livelihoods across the species range
(Zimmermann et al. 2005). The aim of this study is to estimate the mammal species richness and
abundance along the river Rio Carate, which is located at the border of Corcovado National Park, the
Osa Peninsula, Costa Rica. Corcovado National Park compromises primary lowland rainforests, and
serves as an important haven for various animals and plant species. However, for many mammal
species, the area of the park is not sufficient to maintain healthy populations. By using tracking
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Griffiths J, Watteyn C., Karlsdóttir B., McCafferty A., Arton A., Ross A., Wilcox J.
techniques, we can gain knowledge about the mammal species present in and along the border of
the park, and it will give us an idea of which mammals are moving in and out of the park. This is
especially important for feline species, since their broad distribution ranges obligate them to move in
between different protected areas in order to not override their maximum carrying capacities.
Material & Methods
Tracking mammals by following footprints is probably the oldest known method of identifying
mammal’s presence in an area (Bider, 1968). Track surveys are efficient and usually low in cost, but
are dependent on suitable field conditions and trained observers (Burnham et al, 1980; Smallwood &
Fitzhugh, 1995). Track searches were performed along the river Rio Carate, Carate, Osa Peninsula,
Costa Rica; starting at the river estuary, and going two kilometres upstream. The surveys were
carried out during dry season, allowing us to walk and look for tracks in and around the riverbed. We
started at 7:00 am to prevent tracks from begin vanished. More than 200 mammal species are
currently present in the different forest types of Costa Rica. This study focuses on 20 mammal
species. Table 6 gives an overview of the 19 selected mammal species. All species are found in the
lowland rainforests of the Osa Peninsula (Cavalcanti & Gese, 2009). Among the focal species’
distribution range, only the Baird’s tapir is listed as Endangered. Many other mammal species are
listed as globally Vulnerable or Near threatened (IUCN, 2014). However, in Costa Rica, the six feline
species, Neotropical river otter and Paca are considered to be Endangered (Cavalcanti & Gese, 2009).
All mammal tracks were recorded and identified by measuring its widest point and the vertical
distance from the toes to the palm pad (Figure …) and by using mammal track sheets (Adapted and
modified of Sanchez, 1981). The GPS position of the track was noted down as well as the direction of
movement. This gives us information about the movement of individuals within a certain species. If a
track of the same species was found within 100 m from the previous track, it was not recorded since
it would probably be the same individual. Due to the very dry substrate, which is a mix of sand and
rubble, a considerable level of skills is necessary in order to accurately detecting and identifying the
tracks.
Finally, the program Estimate S allowed us to make an estimate about the mammal species diversity.
With this program, we are able to estimate the Simspon’s diversity Index, which is essentially the
probability of two randomly chosen individuals (tracks) being from different species. Furthermore,
we could make an estimate of the evenness, which show how evenly distributed the abundance of
the species is in the area.
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Table 6. Overview of the 20 selected mammal species (IUCN, 2014).
Common species name
Latin species name
IUCN status
Costa Rica status
Baird’s tapir
Tapirus bairdii
Endangered
Endangered
Collared peccary
Peccari tajacu
Least concern
Least concern
White-lipped peccary
Tayassu peccary
Vulnerable
Endangered
Red brocket deer
Mazama Americana
Data deficient
Data deficient
Tayra
Eira Barbara
Least concern
Least concern
Neotropical river otter
Lontra longicaudis
Data deficient
Endangered
Striped hog-nosed skunk
Conepatus semistriatus
Least concern
Least concern
Common opossum
Dedelphis marsupialis
Least concern
Least concern
Water opossum
Chironectes minimus
Least concern
Least concern
Northern tamandua
Tamandua Mexicana
Least concern
Least concern
White-nosed coati
Nasua narica
Least concern
Least concern
Crab-eating raccoon
Procyon cancrivorus
Least concern
Least concern
Central American agouti
Dasyprocta punctate
Least concern
Least concern
Paca
Agouti paca
Least concern
Least conern
Nine-banded armadillo
Dasypus novemcinctus
Least concern
Least concern
Puma
Puma concolor
Least concern
Endangered
Ocelot
Leopardus pardalis
Least concern
Endangered
Jaguarondi
Puma yagouaroundi
Least concern
Endangered
Margay
Leopardus wiedii
Near threatened
Endangered
Jaguar
Panther onca
Near threatened
Endangered
Figure 2. Standard measurements taken; A- Track widest point and B- vertical distance from the toes to the palm pad.
Results
During this first phase of the mammal track project, we have already some results to show. In total,
over the 13 different surveys, we saw 17 different species, of which one unidentified species and one
unknown cat species. The 15 identified species of our list were: water opossum, common opossum,
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Neotropical river otter, collared peccary, white-lipped peccary, tayra, ocelot, crab-eating raccoon,
white-nosed coati, Central American agouti, nine-banded armadillo, baird’s tapir, red brocket deer
and margay. The overall abundance is 101; meaning that in total we saw about 101 different
individuals over the 13 surveys. The mean species count per sample (or in our case survey) is 4.69;
meaning that on average we see about four different species each survey. The amount of tracks we
saw of each mammal species is given in figure 4. Most of the tracks were from the Neotropical river
otter, followed by the ocelot, Bairds tapir, crab-eating raccoon and white-nosed coati.
Encountered tracks
Encountered mammal tracks per species
20
18
16
14
12
10
8
6
4
2
0
Mammal speices
Figure 4. Graph representing the amount of tracks found per mammal species over the 13 surveys.
Figure 5 shows that the cumulative number of species encountered (y) levels off with the cumulative
number of samples (surveys) carried out over time (x). However, after carrying out a rarefaction, we
see that the curve does not level of that much towards the end, meaning that we probably have not
reached the maximum amount of species present in this area yet.
Rarefaction: A statistical interpolation method of rarefying or thinning a reference sample by drawing random subsets of individuals (or
samples) in order to standardize the comparison of biological diversity on the basis of a common number of individuals or samples.
Species accumulation curve: A curve of rising biodiversity in which the x-axis is the number of sampling units (individuals or samples) from
an assemblage and the y-axis is the observed species richness. The species accumulation curve rises monotonically to an asymptotic
maximum number of species.
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Figure 5. The species accumulation and rarefaction curve.
Table 7. An overview of the species count, cumulative species count, abundance and cumulative sample number. The
species count gives the amount of species found in each sample (survey). The cumulative species count adds the amount of
species found in sample x to the amount of species found in sample x-1. The abundance gives the amount of individuals
over all the species found in each sample. The cumulative sample number gives the amount of samples (surveys) carried
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6
Sample 7
Sample 8
Sample 9
Sample 10
Sample 11
Sample 12
Sample 13
Total
out during the period.
Species count
5
6
4
4
6
3
5
7
7
3
4
3
4
4,69
Cumulative species count
5
10
10
11
13
14
14
14
16
16
16
16
17
17
Abundance
5
6
8
5
8
5
9
22
14
3
7
4
5
101
Cumulative sample number
1
2
3
4
5
6
7
8
9
10
11
12
13
13
Figure 6 gives us the extrapolated species accumulation curve, showing us the equation from which
we can now estimate how many surveys we need in order to observe the maximum amount of
species present in the area. Table … shows us the amount of species we will have throughout the
surveys. So far, we carried out 13 surveys, which gave us 17 species. Based on the formula, we would
have seen around 19 species; which shows that the equation gives us a good estimate on how it is in
reality. If we then, based on the equation, try to estimate how many surveys we need to see a level
off in the amount of species, we fill in e.g. 20 or 30 surveys (=x in the formula), and we see that the
amount of species (=y in the formula) does not stabilizes since the formed equation is a linear
function. This will be discussed later on.
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Log Cumulative Species Number
Extrapolated Species Accumulation Curve
1.4
1.2
y = 0.4495x + 0.7838
1
0.8
0.6
0.4
0.2
0
0
0.2
0.4
0.6
0.8
1
1.2
Log Cumulative Sample Number
Figure 6. The extrapolated species accumulation curve with an equation that gives the relationship between the species
richness and the number of samples (surveys).
cumulative sample number
cumulative species number
log(cumsampleNo)
log(cumspeciesNo)
y2
10^(y)
1
5
0
0,69897
0,7838
6,07855
2
10
0,30103
1
0,91911
8,300667
3
10
0,477121
1
0,99827
9,960153
4
11
0,60206
1,041393
1,05443
11,33512
5
13
0,69897
1,146128
1,09799
12,53104
6
14
0,778151
1,176091
1,13358
13,60126
7
14
0,845098
1,176091
1,16367
14,57711
8
14
0,90309
1,176091
1,18974
15,47886
9
16
0,954243
1,230449
1,21273
16,32045
10
16
1
1,230449
1,2333
17,11197
11
16
1,041393
1,230449
1,25191
17,86101
12
16
1,079181
1,230449
1,26889
18,57342
13
17
1,113943
1,255273
1,28452
19,25385
20
1,30103
1,36861
23,36754
30
1.477121
1.44777
28
Furthermore, the output of Estimate S enables us to give an estimate of the species diversity, such as
the Simpson’s diversity index. The Simpson’s mean (D) is 8.21, and from this we can calculate the
Simpson’s mean index (1-D) with the formula 1-D = 1-(1/D) = 0.878197. Since this is close to 1, it
means we have a high mammal species richness over all the samples (surveys). Using the Simpson’s
diversity index, we can measure the evenness (E) with the formula E = (1/D)/S, with S the amount of
samples (surveys). The result is 0.631538, which is closer to 1, meaning that Rio Carate is
characterized by a quite high evenly distributed abundance of species.
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Discussion
From our results so far, we can say that there are 17 mammal species present and active around Rio
Carate. Since we have only carried out 13 surveys, we cannot say that this is the maximum amount of
mammal species we can found over here. Our extrapolation curve does not level off at the end,
meaning that the equation formulated out of the extrapolation curve is a linear function. Based on
this equation, we cannot calculate how many surveys we need in order to reach the maximum
amount of species. Further research is necessary to get a better equation (e.g. logarithmic equation).
Most of the tracks were identified as Neotropical river otter, which can be mainly explained by the
fact that we are surveying along the river Rio Carate. It is still interesting to see that even though it is
dry season, there are still quite a few otters present in the area. During dry seasons, mammals tend
to move to other places to look for more favourable habitats. They have to look for water and food
resources that they are not finding in the areas they used to live during the wet season. We also saw
quite a lot of tracks from the Ocelot, Bairds tapir, Crab-eating raccoon and White-nosed coati. The
presence of feline species tracks, such as the ocelot, shows that wild cats are moving in and out of
Corcovado National Park. However, more data and analysis is needed to figure out how abundant
they are and to which areas they are moving to and from.
The data during phase one was collected during dry season, probably affecting the encounter
probability as it is thought that mammals move deeper into the centre of a protected area (in this
case Corcovado National Park), looking for food and water resources (reference). In general, the
composition of mammal communities depends on the forest’s ability to support the requirements of
the mammals present in the area. Modification of habitats, such as temporal or spatial changes, may
generate boundaries for species due to the newly created patchiness in the landscape, and this has
effects on the structure and dynamics of all biological communities (Cadenasso et al., 2003). Surveys
carried out over the whole year, will make it interesting to see if there is a difference in the amount
of mammal species and abundance we see during the wet and dry seasons.
During the following phase, we would like to make some changes in our study. Instead of only using
natural mammal tracks, we will use the track boxes of a previous BTEC student and place them
higher up the river since observational walks have shown that there are more tracks present higher
up. We will also continue to collect data from natural tracks, but will extend our trail higher up the
river as so far, we only cover a length of about 2 km. Furthermore, many mammals are shy and
elusive creatures, and their adaptation to live in the undergrowth or canopy, or their nocturnal
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lifestyle makes detection difficult (reference). Over the years, wildlife biologists have used various
tracking techniques to assess mammal populations. The most common method is to detect the tracks
left in fine soil or sand (Olifiers et al, 2011), which is what we did during this phase. However, from
the moment we are able to get a couple of camera traps, we would like to use photo-trapping for our
mammal study. The method is especially efficient for inventories of cryptic animals as well as for
population studies of species for which individuals can be individually recognized by marks (Karanth,
1995; Carbone, 2001). Camera-trapping is an important non-invasive tool for assessing patterns of
mammal abundance and richness throughout space and time, and their link with activity patterns,
habitat use and reproductive information, which are key elements for wildlife conservation research.
Track surveys are efficient and usually involve low costs, but depend on suitable field conditions and
trained personnel (Burnham et al., 1980; Smallwood and Fitzhugh, 1995). Camera-trapping on the
other hand is more costly at the beginning, but is not so dependent on the environment to be
sampled, constant assistance or experienced field staff (Rappole et al., 1985). Once we have our
camera traps, we can combine the data from our track studies with the data from the phototrapping.
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3.2.4 Turtle predation study along Carate and Leona beach, Osa Peninsula.
Introduction
Sea turtles have been swimming in our oceans for millions of years and are a fundamental link in
marine ecosystems by maintaining the health of coral reefs and sea grass beds. They survived
different environmental changes thanks to their special adaptations (Spotilla, 2011). Nowadays, sea
turtles face a whole new range of, basically human-induced, threats including poaching, climate
change, pollution, beach development and artificial lighting (Safina, 2006; Spotilla, 2011), highly
affecting their growth, reproduction and thus survival (Spotilla, 2011). Their temperature-dependent
sex determination makes them an excellent indicator species for climate change, and therefore a
flagship species for conservation. Increasing temperatures create a sex bias skewed towards females,
which can cause entire populations to collapse (Hamann et al., 2007; Valverde et al., 2010; Hawkes et
al., 2011). Their late maturation in conjunction with these anthropogenic threats make turtle
populations highly vulnerable and often unstable (Govan, 1998). A global rise in sea levels causes a
decline in nesting habitat, and changing ocean currents and sea temperature rises lead to decreasing
prey species availability (Fish et al., 2005; Chaloupka et al., 2008; Robinson et al., 2009). Worldwide,
six of the seven sea turtle species are now endangered and threatened with extinction (IUCN, 2016).
Predation, especially on the eggs and hatchlings, highly affects sea turtle populations in a negative
way. Natural predators such as crabs, raccoons, birds, coyotes and sharks play a major role in the
food web. Besides them, also humans are negatively affecting sea turtles by disturbing the nesting
beaches in different ways. People leaving trash near the shore for example, unintentionally invite
other, non-native species to look for food. Furthermore, in Central America, many communities
permit their domesticated dogs and cats to run free in coastal villages, leading to several sea turtle
nests being dug up and females being attacked while nesting. Furthermore, poaching and the illegal
trade of eggs, hatchlings and turtles further reduces the turtle populations. With as few as one in
1000 eggs reaching adulthood, the destruction of only a few nests can have a devastating effect on
any sea turtle population. The main problem is that, sea turtles have developed special adaptations
that allow them to live actively in the water, leaving them very clumsy on the land. They are not fast
enough to escape since they are unable to retract their heads and flippers into their shell, like land
tortoises, making them very vulnerable to these invasive predators (Sea Turtle Conservancy, 2016;
IUCN, 2008).
A number of conservation strategies have been established throughout Costa Rica, including limited
legal commercial egg harvesting on a nesting beach in Ostional during the first 36 hours of wet
season arribadas (mass arrival of turtles) (Campbell, 1998) and an annual catch of 1,800 black turtles
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being granted to fishermen in Limόn (Troëng and Rankin, 2004). The latter may have increased
extractive use along with illegal hunting in the mid-90s, the ban on black turtle fishing and increased
law enforcement since 1999 may have increased female turtle survivorship (Troëng and Rankin,
2004). In other regions such as Tortuguero, the Costa Rican government has made egg poaching
illegal, in addition to prohibiting the trade of calipee, the edible part of the shell (Government of
Costa Rica 1963 and 1969; Troëng and Rankin, 2004). Meanwhile, the growing ecotourism industry in
Costa Rica has provided locals with an alternative source of income and has promoted conservation
throughout the country. To evaluate the effectiveness of such strategies, it is imperative that
monitoring programmes are long term as it can take decades for species with late maturity to show a
population response (Troëng and Rankin 2004; Bjorndal et al., 1999).
Costa Rica is an important nesting area for four sea turtle species: green turtles (Chelonia mydas),
hawksbills (Eretmochelys imbricata), olive ridleys (Lepidochelys olivacea) and leatherbacks
(Dermochelys coriacea) (Drake 1993). All four species have been recorded as nesting in southern
Costa Rica, on the Osa peninsula. Hawksbills and leatherbacks are listed as Critically Endangered,
green turtles are Endangered, and olive ridleys are Vulnerable (IUCN 2013). On the Osa Peninsula,
turtles are threatened primarily from predation by dogs, coastal development, illegal trade of eggs
and, to a lesser extent, turtle meat (Drake, 1996). Therefore, the aim of this project is to monitor the
frequency of predation and the health of the nesting turtle populations. The Frontier Costa Rica
Forest research programme works in partnership with CORTORCO, protecting the four species which
nest here (see above). The hawksbills and leatherbacks rarely nest on these two beaches whereas
the olive ridley is most commonly found nesting here (Troëng and Rankin 2004; Honarvar et al.,
2008; IUCN, 2013).
Material and Methods
During this first phase of 2016 (January-March), we focused on the two common sea turtle species
present in this area; the Pacific green turtle (Chelonia mydas) and the olive ridley sea turtle
(Lepidochelys olivacea). The Pacific green turtle has a circumglobal distribution, occurring in tropical
and subtropical waters; they are migratory species and undertake complex movements and
migrations through geographically different habitats. Nesting takes place in more than 80 countries
worldwide (Hirth, 1997). Their movements within the marine environment are less understood, but
apparently they inhabit coastal water of over 140 countries (Groombridge & Luxmoore, 1989). The
Olive ridley sea turtle has circumtropical distribution, with nesting occurring in tropical waters and
migratory circuits in tropical and subtropical areas (Pritchard, 1969). They nest along the beaches of
nearly 60 different countries.
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Both night and morning patrols were carried out on the beaches Playa Carate and Playa Leona.
Morning patrols began at 05:30 am on Playa Carate and 05:15 am on Playa Leona to minimise
surveyor exposure to direct sunlight and high temperatures. Night patrols typically started at 19:30
pm on both beaches. Each week, the high tide times were checked online in order to fit the morning
and night patrols into the schedule. To minimise the disturbance to nesting females, surveyors were
using red lights during night patrols and survey teams are limited to six people. The survey area for
both beaches is divided into 100 m sectors and each sector has his own number; with a 2.3 km
stretch of Playa Carate and a 2.5 km stretch of Playa Leona. For every turtle track encountered, the
following data had to be collected during the night patrols:
-
Patrol date and names of recorders; this is for having an idea of the survey effort
-
Time of recording; both start and end time of the survey, as well as the time when a nest is
encountered
-
Beach sector number; always taking the smallest number (e.g. if observers are in between
sector 11 and 12, they will write down sector 11)
-
Nest distance to the vegetation; with zone 1 (tidal inundation zone), 2 (beach area) or 3
(vegetation area)
-
Sea turtle species; olive ridley turtle or Pacific green turtle
-
Nest type associated with the tracks: Nest or False nest (N/F); false nest when the turtle
returned to the sea without nesting
-
Track symmetry: symmetrical S or asymmetrical A
After writing down the data, the track was crossed through in the sand to avoid the track being
recorded again in subsequent patrols. The track characteristics were used to identify the species if
the turtles were absent, where asymmetrical tracks suggest Olive ridley and symmetrical tracks
suggest Pacific green. In-situ nests were confirmed by inserting a stick into the sand to locate the egg
chamber (indicated by a marked change in resistance when pressure applied) followed by careful
digging to confirm the presence of eggs. A false crawl was defined by the absence of a nest or where
it was clear that the turtle returned to sea without digging a nest.
During the morning patrols, predation of the nests was also checked. In the case of a predated nest,
obvious by the presence of predator tracks, egg shells and signs that the nest had been dug up, the
following was written down:
-
Patrol date and names of recorders, this is again for having an idea of the survey effort
-
Time of recording, both start and end time of survey, as well as the time when a nest is
encountered
-
Beach sector number, always taking the smallest number
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-
Nest distance to the vegetation: zone 1 (tidal inundation zone), 2 (beach area) or 3
(vegetation area)
-
Sea turtle species: olive ridley turtle or pacific green turtle
-
Nest type associated with the tracks: Nest or False nest (N/F); false nest when the turtle
returned to the sea without nesting
-
Measurement of the length of the tracks (edge to edge) at three different places and taking
the average
-
Track symmetry: symmetrical S or asymmetrical A
-
New or old nest (N/O); if old not re-recording, only if it is predated
-
Predated nest (yes/no)
-
Presence of tracks (yes/no); if possible identifying the predator based on the tracks
-
Percentage of predation
An important note to make, is that every predated nest seen had to be analysed well to be sure that
it is a newly recording predated nest by checking if the eggs are still soft, meaning that the eggs are
recently predated. If a new predated nest is found, dig up the pieces of eggs and try to put them
together to determine the amount of eggs predated.
If nests are found around the lagoon, or the area in front of the airstrip until the coconut bar, we are
relocating the nests.
Results
In progress. During this first phase (January-March), we carried out basic turtle patrols on the
beaches of Carate and Leona. We still have to set up a clear standard protocol together with MINAE
and CORTORCO in order to understand what the main goals are regarding the sea turtle study.
During the upcoming weeks we are going to carry out more morning turtle patrols, depending on the
amount of volunteers present. For now, the point of conducting morning patrols is to check for the
amount of predation and to generally know how much nests were made and by which turtle species.
From June onwards, high turtle season begins, in which we will start to tag nesting turtles and do a
general health check. This will be explained in more detail in the next science report, in which the
collaboration with CORTORCO will be more explained. Furthermore, the data will be analysed
together with CORTORCO and will be reported directly towards MINAE.
Discussion
In progress.
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3.2.5 Birds of Carate lagoon, a study on the species richness and abundance
Introduction
Coastal areas are typically characterised by a high human population density and thus activity,
causing a high pressure on the associated ecosystems, such as lagoons. Increasing human activity
results in environmental deterioration and disturbs biogeochemical processes that are going on in
the lagoons (Seitzing et al., 2005; Halpern et al., 2008; Qu & Kroeze, 2010). Due to ideal
temperatures and precipitation patterns, tropical coastal areas are very productive zones, and are
therefore highly affected by anthropogenic nutrient loading compared to similar habitats at higher
latitudes (Yule et al., 2010; Smith et al., 2012).
Coastal lagoons are shallow waterbodies, spatially separated from the ocean by sandbars and barrier
islands, or temporary separated during certain times of the year (Johnston, 2000). They are highly
productive ecosystems, providing several ecosystem services valuable for society, including fisheries,
storm protection, tourism, etc. (Gönenc & Wolflin, 2005; Anthony et al., 2009). Although, little
changes in water quality can have big effects on the functioning of the lagoon, and all its associated
living organisms. The degree to which a lagoon is sensitive towards changes in water quality mainly
depends on the lagoon type, referring to its exchange rate with the ocean and its size, and on the
faunal and floral communities present in and around the lagoon (Johnston, 2000). Due to the little
amount of information available about the sensitivity of lagoons towards changes in water quality,
there is a need to examine which environmental parameters affect the health of the lagoon in
general, with focus on the bird communities. There are a couple of quality parameters that are
expected to have a big influence on the functioning of lagoons, such nutrient enrichment, turbidity,
toxic contamination and organic enrichment (Johnston, 2000). Especially with changing climate,
these parameters can vary, affecting the physical structure, ecological characteristics and social
values associated with lagoons. Expected shifts in physical and ecological features range from
changes in flushing regimes, freshwater inputs, water chemistry to inundation and habitat loss
(Anthony et al., 2009). Gathering more information about coastal lagoons, especially in the context
of climate change, is critical. In this study, the bird species richness associated with a tropical lagoon,
situated in Carate, Osa Peninsula, Costa Rica, is studied; as well as their response upon changes in
environmental parameters. In addition, evidence from the few lagoon-specific studies undertaken, it
is suggested that once impacted (particularly by nutrient enrichment) lagoons may recover slower
from impacts due to changes in water quality. This highlights the need to identify water quality
impacts within lagoons as early as possible and suggests the need for a precautionary approach to
interpreting and acting on information that may indicate an impact (Johnston, 2000).
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In this study, we want to examine the health of the lagoon Peje Perro in Carate. By surveying the bird
species richness and abundance, we can have an idea about the functioning of the lagoon.
Furthermore, we want to gain more information about different environmental parameters, their
change over time and the effect on the bird diversity.
Material and methods
The study is carried out at the coastal lagoon Peje Perro, located on Carate beach, Carate, Osa
Peninsula, Costa Rica (Figure ). During dry season (December-may), the lagoon is separated from the
Pacific ocean, changing the internal characteristics (e.g. salinity, nutrient concentration, turbidity).
Heavy rains allow the lagoon to connect again with the ocean. The lagoon is surrounded by lowland
rainforest and gets is disturbed by activities of local fisherman and tourists staying at the surrounding
ecolodges. A group of minimum three and maximum five observers are carrying out the survey at
two different spots close to the lagoon. Minimum three persons are necessary to fulfil the health and
safety requirements of Frontier Costa Rica Project (see earlier), and a maximum of five persons
allowed us to minimize the disturbance on the foraging behaviour of the birds during the survey. The
spots were chosen in such a way that we are close enough to see and identify the birds without
disturbing them too much. Once arrived at the survey point, all the different bird species present in
the lagoon, on the sandbanks as well as in the vegetation surrounding the lagoon were noted down.
We did not include the bird species present in the lowland rainforest starting right behind the lagoon
since these bird species are more likely to be part of the forest ecosystem. Using binoculars and the
bird identification books (Garrigues, 2014), we identified all the seen species during the survey. If we
were not able to identify them, pictures were taken and identified back on camp.
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Results
During this first phase of the year, we were able to identify 29 different lagoon bird species present
in and around the lagoon of Carate. Table … gives an overview of the found species, saying which
species we found in the morning, afternoon or both.
Rarefaction curve Lagoon birds
Number of species
35
30
25
20
15
Afternoon
10
Morning
5
0
0
2
4
6
8
10
12
14
Cumulative sample (survey) number
Figure …
Simpsons index and Eveness
0.900
0.800
0.700
Axis Title
0.600
0.500
morning
0.400
afternoon
0.300
0.200
0.100
0.000
SIMPSON
EVENESS
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ACE and CHAO1
30
25
Axis Title
20
morning
15
afternoon
10
5
0
ACE
CHAO1
According to the above graphs, the ACE and CHAO1, which represents the species richness of the
lagoon birds is higher during the afternoon then the morning. If we then have a look at the Simpsons’
index and Evenness, we see that the morning surveys show a higher species diversity. This means,
that if we take into account the abundance within each species observed, the species diversity is
higher in the morning; so basically it means that during the afternoons there are a slightly more
species
found,
but
in
lower
39
amounts
so
they
do
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Lagoon bird species comparison morning / afternoon
MORNING
AFTERNOON
120
Absolute amount of seeings
100
80
60
40
20
0
Lagoon bird species
Figure … Comparing the amount of individuals within each species between morning and afternoon surveys.
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From the above curves we can see that we didn’t reach the maximum amount of species present in
the area yet. This is because the curve does not really levels off at the end. With the equation we
could estimate how many surveys we need to level off the curve, so to see when we reach the
maximum amount of species. However, since we do not yet see a level off, the equation is not totally
correct and we need more samples (surveys) in order to make a more representative equation.
The Simpson’s mean (D) is 6.6, and from this we can calculate the Simpson’s mean index (1-D) with
the formula 1-D = 1-(1/D). The result is 0.848485. Since this is close to 1, it means we have a high bird
species richness over the surveys. Using the Simpson’s diversity index, we can measure the evenness
(E) with the formula E = (1/D)/S, with S the amount of samples (surveys). The result is 0.55.
32,33
0
47,27
Respectively ACE, ICE and CHAO1
0
28,49
Discussion
We compared the Lagoon bird species richness between morning and afternoon surveys and found …
If we combined all the data (morning and afternoon data) all together, we found…
From these results we can say that…
Furthermore, it should be mentioned that this is the first time we carry out a lagoon bird study.
During the first weeks, observers had to get to know the birds and needed more time to identify
them. Now, we are more skilled and are able to spot and identify the different bird species more
easily.
During the next phase we would like to add how disturbance have an effect on the species richness
and abundance of the lagoon birds. By comparing surveys with (human) disturbance to surveys
without (human) disturbance, we can see if by kayaks, fisherman, etc. have a negative influence on
the bird diversity in the lagoon. It could be noted that we, as observers, also disturb the birds present
in and around the lagoon. However, since we see a high species richness, we can say that our
presence has none or very low effect on their behaviour.
Another idea is to include different environmental parameters into the study. Since it is known that
salinity, temperature, pH, depth, etc. influence the functioning of lagoon ecosystems, it is important
to know have they vary over time and if this influences the presence of bird species in and around
the lagoon. In order to carry out this extra measurements, we need to contact MINAE and follow the
standard protocol for water quality monitoring.
Finally, we would like to use kayaks during the next phase in order to get around the whole lagoon.
We will go into the water before sunrise and found fixed spot in the lagoon and wait until birds
arrive. In this way, we don’t disturb them since we are not moving in the kayak.
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3.2.6 Bird species richness and abundance in primary, secondary and degraded forest
Introduction
The highly heterogeneous environments of Costa Rica give rise to many species-rich communities;
particularly those within the bird families (Herzog, Kessler & Cahill, 2002). Costa Rica hosts
approximately 850 bird species, of which 160 species are endemic to country (Henderson, 2010). This
high bird species richness means that Costa Rica has a relatively long history of studies focusing on
bird community structure (e.g., Young et al, 1998; Blake & Loiselle, 2001; Sigel et al, 2006) and
demography (e.g., Ruiz-Gutiérrez et al, 2008; Young et al, 2008; Woltmann & Sherry, 2011). Birds
provide various important ecological functions, such as seed dispersion and pollination, and can
therefore help in the maintenance of plant communities, and even contribute towards the
reforestation of fragmented habitats (Pejchar et al. ,2008). However, the majority of bird studies
have been carried out in pristine habitats with very little attention given to degraded or fragmented
areas (Wilson, Collister & Wilson, 2011). Furthermore, partly due to its remoteness, little is known
about the bird communities of the Osa Peninsula despite its extraordinary species diversity and high
levels of endemism (Wilson, Collister & Wilson, 2011).
Home to approximately 375 species of birds (or 420 species according to Garrigues, 2007), including
many migratory birds and 18 endemic species (Sanchez-Azofeifa et al, 2002), the Osa Peninsula
comprises one of the largest remaining tracts of intact lowland rainforest in Mesoamerica (Barrantes
et al, 1999). This provides important habitat for a myriad of bird species. While 39% of the region is
under the protection of Corcovado National Park, in recent decades significant development,
deforestation and forest fragmentation has occurred outside of the reserve (Sanchez-Azofeifa et al,
2002).
Deforestation and fragmentation is considered the primary threat to birds in the Osa Peninsula (Osa
Conservation, 2016). Due to a human population growth rate of 2.6% (Sánchez-Azofeifa et al, 2001)
and increases in ecotourism, large areas of forest have been cleared to make space for agricultural
practices and the hospitality industry (Minca & Linda, 2002). Studies have found that in the period
between 1979 and 1997 the percentage of forested area in the Osa decreased from 97% to 89%
(Sanchez-Azofeifa et al, 2002). Furthermore, Sanchez-Azofeifa et al (2002) found that as of 1997, the
majority of the remaining forest outside of Corcovado National Park has been altered, with only 44%
of the region representing mature forest. Today, the tropical forest exists as a patchwork of various
size, age and connectivity within a human-dominated landscape (Wilson, Collister & Wilson, 2002).
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Particular bird groups, such as understory insectivores (Canaday, 1996; Sekercioglu et al, 2002; Sigel
et al, 2006), can be very sensitive to such changes whilst others are able to utilise degraded and
fragmented habitats (Wilson, Collister & Wilson, 2002). Development is likely to continue in the Osa
Peninsula and thus it is of the utmost importance to understand how birds, outside of Corcovado
National Park, are being affected by these changes.
In addition to deforestation and fragmentation the birds of the Osa Peninsula are up against another
threat: climate change. This threat is not unique to the region, however, changes in temperature,
precipitation and greater climatic extremes are likely to have significant impacts on the avifauna. Due
to the fact that birds are endothermic, increased temperatures may cause greater energy use for
thermoregulation (Wormworth & Mallon, 2006). Additionally, temperature changes can indirectly
affect the birds reproduction, timing of breeding and migration (Wormworth & Mallon, 2006). For
example, shifts in temperatures cause birds to shift the timing of seasonal events such as egg laying
or migration (Wormworth & Mallon, 2006). This causes birds to be out of synchrony with other
species, particularly plants and insects, which are necessary for their survival (Wormworth & Mallon,
2006). Such changes may significantly impact species’ reproductive success which could ultimately
result in the collapse of breeding populations in the long-run (Wormworth & Mallon, 2006).
Precipitation changes are also expected to negatively affect bird populations. Studies have shown
that periods of low or zero rainfall are correlated with lower bird populations due to reduced food
availability (Wormworth & Mallon, 2006). Furthermore, it is believed that climate change is likely to
increase extreme weather events such as drought or flooding (Wormworth & Mallon, 2006). Extreme
conditions can alter important habitats and reduce the survival rates of both young and adult birds.
Moreover, drought or floods in critical stopover areas along bird migration routes can impair
migratory birds’ ability to reach their final destination (Wormworth & Mallon, 2006). Altogether, the
effects of climate change and birds responses to it will vary from species to species, thus it is critical
that the different species of the Osa Peninsula are monitored in order to determine how they are
being affected.
Overall, the high species diversity and endemism of the avifauna in the Osa Peninsula coupled with
the threats of deforestation, fragmentation and climate change, highlights the need to better
understand and monitor the birds in the region. Due to the lack of scientific studies on birds in the
Osa Peninsula, Frontier aims to determine the species richness and abundance of birds in Carate in
relation to their habitat and disturbance since bird distribution and species richness is often
explained by habitat type and environmental characteristics. Therefore, thanks to their sensitivity
towards environmental changes, birds are good indicators of habitat health (Wilme & Goodman,
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2003). Monitoring trends in bird diversity may help to identify species at risk of population decline or
even extinction due to human-induced environmental changes, such as habitat fragmentation and
loss, climate change, pollution and pet trade (Pejchar et al., 2008).
As such, the main objective is to compare the species richness and abundance between disturbed,
secondary and primary forest habitats through point count surveys whereby the bird species are
recognized by sound and sight. In addition, Frontier aims to support the goals of the National Parks
Service in the United States of America and MINAE by monitoring migratory birds species that inhabit
both North America and migrate to Costa Rica during winter periods. Finally, due to the sensitivity of
birds to climate change, Frontier aims to monitor the bird species diversity and abundance in
conjunction with climatic changes over the long term.
Material and Methods
This study focuses on 44 bird species, and the species are selected based on the following criteria;
endemic species, data deficient/poorly studied species, specialist species, migratory species, species
under threat (according to the IUCN) and species that perform a high ecological function. Worldwide,
the most important places for habitat-based conservation of birds are the Endemic Bird Areas (EBAs).
Most of the bird species are widespread and can inhabit large ranges of habitats. Some however are
said to be endemic since they are restricted to specific areas due to food and habitat requirements.
The landscapes where these species occur are high priority for broad-scale ecosystem conservation.
EBA’s are found around the world, but most of them are located in the tropics and subtropics,
especially the tropical lowland forest and moist montane forest. Geographically, EBA’s are often
islands or mountain ranges (Birdlife International, 2008). The poorly studied species are species with
very few or deficient data available about their status, distribution, abundance, etc., which makes
them highly prioritized species to study. Specialist species are occurring in certain habitats because of
specialist habitat or food resource needs. If their habitat disappears, it is very likely that the species
disappears will disappears too. Regarding the migratory species, we are working together with the
American National Park of North America and Canada. The bird species that are migrating from north
to south during northern hemisphere winters are being studied since little information is available
about these species when they are moving towards the south. Finally, the bird species with
important ecological functions are also our focus on species, since they have important functions
within the ecosystem they live. For example, woodpeckers make holes in trees that are habitats for
other species such as bats, beetles, etc.
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Table …: Overview of the selected 44 bird species on study.
Bird species common name
Bird species Latin name
Selected criteria
Fiery-billed Aracari
Pteroglossus frantzii
Endemic species to Pacific Costa Rica
and Western Panama
Chestnut-mandibled Toucan
Ramphastos swainsonii
Vulnerable
Black-bellied Wren
Pheugopedius fasciatoventris
Endemic species to Pacific Costa Rica
and Western Panama
Riverside Wren
Cantorchilus semibadius
Endemic species to Pacific Costa Rica
and Western Panama; Data deficient
Cherries Tanager
Ramphocelus costaricensis
Endemic species to Pacific Costa Rica
and Western Panama; Data deficient
Blue-crowned Manakin
Lepidothrix coronata
Endemic species to Pacific Costa Rica
and Western Panama
Red-capped Manakin
Ceratopipra mentalis
Orange-collared Manakin
Manacus aurantiacus
Endemic species to Pacific Costa Rica
and Western Panama
Pale-billed Woodpecker
Campephilus guatemalensis
Specialist
species;
Ecologically
important function
Golden-naped Woodpecker
Melanerpes chrysauchen
Endemic species to Pacific Costa Rica
and Western Panama
Long-tailed Woodcreeper
Deconychura longicauda
Near threatened
Bright-rumped Atilla
Attila spadiceus
Disturbance indicator
Rufous Mourner
Rhytipterna holerythra
Rufous Piha
Lipaugus unirufus
Specialist species
Tawny-Crowned Greenlet
Hylophilus ochraceiceps
Specialist species; Data deficient
Scarlet Macaw
Ara macao
Data deficient
Turquoise Cotinga
Cotinga ridgwayi
Endemic species to Pacific Costa Rica
and Western Panama; Vulnerable
Yellow Warbler
Setophaga petechia
Migratory species
Golden-winged Warbler
Vermivora chrysoptera
Migratory species
Blue-winged Warbler
Vermivora cyanoptera
Migratory species
Black-hooded Antshrike
Thamnophilus bridgesi
Endemic speices to Pacific Costa Rica
and Western Panama; No data
Black-cheeked Ant-tanager
Habia atrimaxillaris
Endemic species to the Osa Peninsula;
Endangered
Bicoloured Ant-bird
Gymnopithys leucaspis
Dot-winged Antwren
Microrhopias quixensis
Specialist species
Ruddy-tailed Flycatcher
Terenotriccus erythrurus
Specialist species
Sulphur-rumped Flycatcher
Myiobius sulphureipygius
Yellow-billed Cotinga
Carpodectes antoniae
Endemic to Costa Rica; Endangered
Baltimore Oriole
Icterus galbula
Migratory species
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Griffiths J, Watteyn C., Karlsdóttir B., McCafferty A., Arton A., Ross A., Wilcox J.
Rufous-tailed Jacamar
Galbula ruficauda
Disturbance indicator
Wood Thrush
Hylocichla mustelina
Near threatened; Migratory species
Smooth-billed Ani
Crotophaga ani
Disturbance indicator
Common Potoo
Nyctibius griseus
Poor data; Vulnerable
Great Tinamou
Tinamus major
Poor data; Climate change indicator
Great Curassow
Crax rubra
Vulnerable; Climate change indicator
Spectacled Owl
Pulsatrix perspicillata
Ecologically important function
Crested Guan
Penelope purpurascens
Poor data
Marbled wood Quail
Odontophorus gujanensis
Near Threatened
Spot-crowned Euphonia
Euphonia imitans
Endemic species to Pacific Costa Rica
and
Western
Panama;
Specialist
species
Green-shrike Vireo
Vireolanius pulchellus
Data deficient
Mealy Parrot
Amazona farinosa
Ecologically important function
White-crowned Parrot
Pionus senilis
Poor data; Ecologically important
function
Brown-hooded Parrot
Pyrilia haematotis
Poor data; Specialist species
Black-Throated Trogon
Trogon rufus
Poor data
Baird’s Trogan
Trogon bairdii
Endemic species to Costa Rica; Near
Threatened
Using point counts, estimates of the bird species richness and abundance can be made. Point counts
are a widely used method to assess the distribution patterns and relative abundance of birds in
tropical habitats (Miller et al., 1998; Sánchez-Azofeifa et al., 2001; Henderson, 2010). A point count
refers to a count carried out by someone that is standing at a fixed place, from which the target
species (birds) are counted by sight and call, and this for a fixed period of time (Bibby et al., 2000;
Gibbons & Gregory, 2006; Hartley & Greene, 2012). The methodology is quite straightforward and
observers can easily gather the required data by walking a trail and stop at different points to record
all the present bird species by sound and sight. It must be said that, due to the high level of tree
density within a tropical forest as well as the very high species diversity in this region, there is quite a
high level of experience necessary to detect and identify birds accurate. The point counts are carried
out along all the different trails; Luna ridge, Leona ridge, Shady lane, Beach trail, Rio Carate, Attalea
loop, road. During each survey, three point counts are carried out, separated 250 m from each other
and started at 100 m from the forest edge. Since we work with a distance radius of 0 – 30 m (1), 30 –
100 m (2) and >100 m (3), it is important to stick with the 250 m in between the point counts to avoid
an overlap of counts. Furthermore, it is important to take into account the effort efficiency of the
observers. This is why we chose to do not more than three point counts during every survey since
there is a drop in focus over time, making it important to find a compromise between collection
47
CRF161
Griffiths J, Watteyn C., Karlsdóttir B., McCafferty A., Arton A., Ross A., Wilcox J.
effort and precision / accuracy (Verner, 1985). Before starting the recording period of ten minutes,
there is a two minute settling period to allow the birds coming back after our disturbance from
walking towards the point counts. The point counts are permanent points, which are permanently
chosen locations within a site and clearly marked with colourful tape flags (Huff et al., 2000). All the
birds that are seen and heard within the different radius are noted down (sight: S; sound: H), as well
as the flying-over and flying-thrus birds are recorded in a separate list as respectively FO and FT.
3
2
1
Figure …: Graphic view of the distance radius used during the point counts.
Results
In progress. So far, only pilot studies have been carried out since all the staff members as well as the
volunteers are still in the process of learning the bird calls and recognizing them by sound and sight.
Furthermore, we will start to use bird sound recording equipment in order to record the bird calls in
the field and identify them back on camp by using the online catalogued bird calls. In this way we will
have a more reliable dataset by double checking our bird call recognizing skills in the field with the
recordings. Furthermore, we can analyse how are skills are improving over time by correlating our
field notes with the recordings checked on camp.
Discussion
In progress.
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Griffiths J, Watteyn C., Karlsdóttir B., McCafferty A., Arton A., Ross A., Wilcox J.
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