Review
1
Golden Hamster and Habitat Preference:
A Review of the Literature
Jeannette M. Erb
Algoma University College
RUNNING HEAD: Golden Hamster
SP
PS YC
ERB
90/91
RESERVE
Review
2
Golden Hamster and Habitat Preference:
A Review of the Literature
Structural and behavioral traits of animals
have evolved over generations,enabling individuals
to cope with changes in the environment and increase
fitness and their reproduction of offspring. These
traits were not necessarily essential for the survival
of the individual, but they must have been advantageous
to survival or they would have been selected out
(Klopfer,1969). For example, different species of
birds have different sizes and shapes of beaks depending
on the food available to them in their habitat.
If they have to dig in the ground for their food,
they may have long pointed beaks; but if they eat
grain on top of the ground, they may have short
beaks.
This evolving of the traits is what Charles
Darwin (1859) referred to as natural selection.
Within any population of animals of the same species
there is variation among individuals and much of this
variation is due to heredity. Many more individuals
are born into a certain species than survive to
Review
3
maturity. The likelihood of an individual surviving
to maturity depends on particular traits it inherits
from its parents. If these traits help the individual
to survive to maturity then these traits will be
passed on to their offspring (McFarland,1982).
The number of generations these traits will be passed
on depends on the breeding success of the parents
and the value of the trait, that is, how helpful
the trait is in in the survival of the animal.
If the trait is no longer advantageous to survival
then it may follow that the trait will no longer
be inherited by future generations.
Habitat selection is one of these traits that
has been part of the evolutionary process. If an
animal chooses its habitat then according to evolutionary
theory the habitat would be based on the best area
to increase fitness (Alcock,1984). Animals select
their habitat by weighing the costs and benefits
of such things as weather, food, and predators.
For example, if an animal has found a possible location
to live that is very warm and sunny most of the
year (their preferred climate in this case) yet the
Review
4
animal must travel a few miles every day for food
then that animal must weigh the costs and benefits.
If the benefits of the warm sunny place outweigh
the costs of travelling for food then the animal
will probably choose to live there. If the costs
are too high then the animal will move on and search
for another place to live. Many studies have been
conducted to test the genetic basis of habitat selection.
One of the ways habitat selection has been studied
is through habitat preference tests. Habitat
preference means when certain species live in the
same area or the same type of area that take into
account terrain characteristics, nesting, singing,
feeding and drinking sites, food availability, and
other animals that may cause overcrowding or may be
predators (McFarland,1982).
Wecker (1963) studied habitat preference in
deermice captured from the field (their natural
habitat) and offspring from these captured mice
that were raised in the laboratory. The mice were
given experience in either a field area, a wooded
area, or a laboratory-type area with unnatural
Review
5
conditions. After they received this experience
both laboratory reared mice and field mice were
placed in an area that was half field and half
wooded area. Laboratory reared mice given experience
in the field and the laboratory setting showed a strong
preference for the experimental field. Mice given
experience in the wooded areas showed no preference
for either habitat. The mice captured from the
field showed a strong preference for the experimental
field independent of the area they were given
experience in. Therefore deermice do show a preference
for their natural habitat regardless of experience.
Klopfer and Hailman (1965) studied habitat
preference in the chipping sparrow. Three groups
of sparrows were used; sparrows caught in the wild
where their habitat preference was determined as
being pine needles over oak leaves, birds hand-reared
in a room devoid of foliage, and birds hand-reared
in the presence of oak leaves. The birds were then
placed in a large outdoor area which included a
mixture of pine and oak trees. The birds captured
from the wild and the birds reared without foliage
Review
6
showed a strong preference for pine needles. The
birds raised with oak leaves showed a split preference
for both oak and pine trees but by the time they
reached twelve months old, all birds in this group
showed a strong preference for pine needles as their
habitat. This study shows that the chipping sparrow
shows a strong preference for its natural habitat
regardless of experience.
Studies like those of Wecker (1963) and Klopfer
and Hailman (1965) show that some animals can exhibit
habitat preferences and that these preferences remain
over time even for those animals raised in the
laboratory aid have had no experience in their natural
habitat. Studies examined habitat preference for
one or two generations only but did not examine if
this preference would evolve over numerous generations
of species raised in the laboratory. The type of
study using numerous generations would be very
difficult to do since studying each generation takes
a lengthy amount of time and studying numerous generations
would take many years. A feasible way of doing
this type of study would be to study an animal that
Review
7
has already been out of its natural environment
for many generations. The golden hamster (Mesocricetus
auratus) is one such animal.
The first published mention of the golden hamster
was in 1839 when Waterhouse briefly mentioned this
species in a paper by saying the the golden hamster
was much smaller than the common hamster and was
identified by its deep golden color. The golden
10
hamster was not mentioned again for almost 100 years
when in 1930, I. Aharoni, on expedition in northern
Syria dug out an adult female hamster and twelve
young from a burrow 2.5 m deep. Wild hamsters live
in steppe areas and cultivated agricultural areas
on the -16- 1a. in -s of northern Syria bordering Turkey.
They burrow deep into the ground with their burrows
consisting of six to eight escape tunnels leading
to different areas. They have different rooms for
nesting, excreting, and storing food, with the
nesting area being the only room lined with alfalfa
grass. Their natural food includes seed, grain,
and hard, dry vegetation. They will also eat fresh
foods such as carrots, lettuce, apples, or live
Review
8
crickets (Roberts,1974).
Hamsters are nocturnal, that is, they are most
active at night. Hamsters are also hibernators
when temperatures reach below 50°F and they will
aestivate, which is a deep sleep-like hibernation,
when temperatures reach above 80°F. A full-grown
hamster weighs on average 150 grams, has a life
expectancy of one and a half years, and exhibits
high fecundity. Females breed at thirty days old
and males at sixty days old but it is possible to
breed at a much younger age. A female has a 4 day
estrus cycle and a gestation period of 16 to 19
days. This is the shortest gestation period of all
mammals except for the marsupials. Hamsters can
have five or six litters a year and each litter
consists of between six and twelve young.
Within one year of Aharoni's excavation of the
hamsters he had approximately 150 hamsters. He
found that they were easy to tame and would make
wonderful laboratory animals and household pets.
The first set of golden hamsters was brought to
North America in 1938. All hamsters found in pet
Review
9
stores today originated from that first set of hamsters
brought from northern Syria (Roberts,1974). This
means that the golden hamster has been out of the
wild for just over 50 years. Since hamsters can
produce approximately five litters a year and can
breed at 30 days old this means that as many as
360 generations of hamsters have been raised in
an environment different from their natural
environment.
Since the golden hamster is easy to work with,
easily accessible, and has been out of its natural
environment for many generations, it provides an
ideal species to expand on previous habitat preference
experiments, in which only one or two generations
were studied. If the golden hamster still prefers
its natural environment over the environment North
Americans have been housing them in for years
(narrow lining of wood chips and a running wheel),
then the inherited trait of preference for habitat
is still present. It has not been actively selected
out of the hamster in the laboratory therefore it
must still be advantageous to the golden hamster.
Review
10
Alcock, J. (1984). Animal behavior: An evolutionary
approach. Sunderland: Sinauer Associates.
Darwin, C. (1859). On the origin of species by
means of natural selection. New York: D. Appleton.
Klopfer, P.H. (1969). Habitats and territories:
A study of the use of space by animals. New
York: Basic Books.
Klopfer, P.H., & Hailman, J.P. (1965). Habitat
selections in birds. In D.S. Lehrman, R.A. Hinde,
& E. Shaw (eds.), Advances in the study of behavior
(pp. 279-303). New York: Academic Press.
McFarland, D. (1982). The oxford companion to animal
behavior. New York: Oxford University Press.
Roberts, M.F. (1974). Teddy bear hamsters. Toronto:
Clarke, Irwin, & Company.
Wecker, S.C.
(1963). The role of early experience
in habitat selection by the prairie deer mouse.
Ecology,
307-325.
Golden Hamster
1
The Effects of Choice Between
A Natural Environment and a Laboratory Environment
In the Golden Hamster
Jeannette M. Erb
Algoma University College
RUNNING HEAD: Choice in the Golden Hamster
Golden Hamster
2
Abstract
Habitat Selection, an evolutionary trait, has been
studied using habitat preference tests which found
that animals prefer their natural habitats or their
parents' natural habitats, if they themselves were
raised in the laboratory. This study examined a
species who has for numerous generations been raised
in the laboratory to see if habitat preference still
exists. The golden hamster, an animal that has been
out of the wild for over 50 years, was used. Sixteen
golden hamsters were randomly assigned to either
an environment simulating their natural environment
or a laboratory environment. After one week's experience
in the environment a three day preference test was
conducted in which each hamster was given a choice
between the natural envtronment or the laboratory
environment. Results indicate that the golden hamster
still prefers its natural environment regardless
of the environment in which it was given experience.
The study demonstrates that evolutionary traits
persist for a long time.
Golden Hamster
3
The Effects of Choice Between
A Natural Environment and a Laboratory Environment
In the Golden Hamster
Many more individuals are born into a certain
species than survive to maturity. The likelihood
of an individual surviving to maturity depends on
particular traits it inherits from its parents.
If these traits help the individual to survive to
maturity then these traits will be passed on to
their offspring. The number of generations these
traits will be passed on depends on the breeding
success of the parents and the value of the trait,
that is, how helpful the trait is in the survival
of the animal. If the trait is no longer advantageous
to survival then it may follow that the trait will
no longer be inherited by future generations. Charles
Darwin (1859) proposed the method of natural selection
as the process for passing on these traits over
generations.
Structural and behavioral traits of animals
have evolved over generations, enabling individuals
to cope with changes in the environment while increasing
Golden Hamster
4
their fitness and their reproduction of offspring.
For example, different species of birds have different
shapes and sizes of beaks depending on the food
available to them in their habitat. If they have
to dig in the ground for their food, they may have
long pointed beaks; but if they eat grain on top
of the ground they may have short beaks. These
traits were not necessarily essential for the survival
of the individual, but they must have been advantageous
to survival (Klopfer,1969).
Habitat selection is one of these traits that
has been part of the evolutionary process. According
to evolutionary theory the habitat an animal chooses
is the best area to increase fitness (Alcock,1984).
Animals select their habitat by weighing the costs
and benefits of such things as weather, food, and
predators. Many studies have been conducted to
test the genetic basis of habitat selection. One
of the ways habitat selection has been studied is
through habitat preference tests. Habitat preference
means when certain species live in the same area
or the same type of area that takes into account
Golden Hamster
5
terrain characteristics, nesting, singing, feeding
and drinking sites, food availability, and other
animals that may cause overcrowding or may be predators
(McFarland, 1982).
Habitat preference tests have been conducted
by such experimenters as Wecker (1963) and Klopfer
and Hailman (1965). As an example, Wecker (1963)
studied habitat preference in deermice captured from
the field (their natural habitat) and offspring from
these captured mice that were raised in the laboratory.
The mice were given experience in either a field
area, a wooded area, or a laboratory-type area with
unnatural conditions. After they received this
experience both laboratory reared mice and field
mice were placed in an area that was half field and
half wooded area. Mice given experience in the
wooded areas showed no preference for either habitat.
The mice captured from the field showed a strong
preference for the experimental field independent
of the area in which they were given experience.
Laboratory reared mice given experience in the field
and the laboratory setting showed a strong preference
Golden Hamster
6
for the experimental field. Therefore, this shows
that animals, in this case deermice, do prefer their
natural environment regardless of experience.
Studies like those of Wecker (1963) and Klopfer
and Hailman (1965) show that some animals can exhibit
habitat preferences and that these preferences remain
over time even for those animals raised in the laboratory
and have had no experience in their natural habitat.
Stifdies examined habitat preference for one or two
generations only but did not examine if this preference
would evolve over numerous generations of species
raised in the laboratory. The type of study using
numerous generations would be very difficult to do
since studying each generation takes a lengthy amount
of time and studying nuterous generations would take
many years. A feasible way of doing this type of
study would be to study an animal that has already been
out of its natural environment for many generations.
The golden hamster (Mesocricetus auratus) is one
such animal
In 1938 the first set of wild golden hamsters
were brought to North America and all hamsters found
Golden Hamster
7
in pet-stores today originated from that first set
of hamsters. Since hamsters average five litters
a year and they can breed at approximately thirty
days old this means that as many as 360 generations
of hamsters have been raised in an environment different
from their natural environment.
Since the golden hamster has been out of the
wild for so many generations one might wonder whether
they still prefer their natural habitat. My experiment
examined this question by giving hamsters experience
in either an environment similar to their natural
environment or an environment similar to their
environment of the last fifty years. All hamsters
were then allowed to choose between the two environments.
Method
Subjects
Sixteen golden hamsters (Mesocricetus auratus)
of both genders were randomly assigned Into one of
two groups.
Apparatus
Aquariums housed the hamsters in order to
facilitate observation. One group of aquariums
Golden Hamster
8
attempted to approximate aspects of the hamsters'
natural environment. The aquariums were half filled
with soil and alfalfa straw was spread on top. Food
was scattered throughout the cage area and a small
dish of water was buried in order to resemble a
small pond. This I labelled the Natural Environment.
The other group of aquariums were similar to
the typical Pet-Store Environment of the hamster
which is woodchips, food, water, and a running wheel
yet different enough from the Pet-Store Environment
to be novel to the hamster. The aquariums were lined
on the bottom with shredded newspaper 4.5 cm thick.
Food was placed in the same spot everyday and a
water tube was secured to the glass. This I labelled
the Laboratory Environment.
Procedure
The sixteen golden hamsters were on average
one month old at the start of the experiment. Since
hamsters are nocturnal, before being randomly assigned
into the experimental groups the hamsters had their
cycle artificially changed with a 12 hour lights on
at night and a 12 hour lights off during the day.
Golden Hamster
9
Observations were made during the day and a red
light was turned on which the hamsters cannot see
yet the observer can (Zucker & Stephan,1973). Room
temperature was kept at 20°C.
Once the hamsters were accustomed to the move
to the laboratory, they were randomly assigned to
one of two groups; either the Natural Environment
or the Laboratory Environment. The hamsters were
placed separately in the aquariums. The hamsters
were given one week experience in the environment.
There was little human contact and the only changes
made in the environment were the changing of food
and water.
After the week of experience a preference test
was conducted. A wooden box was set up yh gr e half
.
,
of it vas set up like the Natural Environment and
the other half was set up like the Laboratory Environment.
Each hamster was placed separately in the middle of
the preference test box and observed for a twenty
minute period. The time spent in each half of the
box was recorded. The preference test was done
three times over three days for each hamster.
Golden Hamster
10
This experiment was conducted two times with
two groups of eight hamsters due to housing availability
and time factors.
Results
A t-test was computed for the Natural Environment
group and there was a significant difference between
preference for sides (440=21.61,p<.05). The Natural
Environment group preferred the Natural Environment
side. The Laboratory Environment group also showed
a significant preference for the Natural Environment
side (to0=22.07,p<.05).
Insert figure 1 about here
A t-test was computed for the difference between
the Natural Environment group and the Laboratory
Environment group. There was no significant difference
(tNa=1.39,p>.05). However, on the third day of the
preference test there was a significant difference
between the groups (toir2.2,p<.05).
Insert figure 2 about here
Golden Hamster
11
Discussion
As the results show, even after fifty years
out of the wild the golden hamster still prefers
its natural environment regardless of the environment
it was given experience in. One hundred percent
of the hamsters in this experiment spent more time
that is, more than 50% of the time on the Natural
Environment side. Therefore there was no effect oil
experience overall. On the third day though there
was a difference between groups. There could be
a few explainations for this. One could be that
the Natural Environment group adapted better to the
preference test because of their experience in the
Natural Environment. If the preference test had
been conducted for more days the difference between
groups may have been lower. Another explai nation
-
is the outliers. If you eliminated the two outliers
from the Laboratory Environment group there would
be no difference between groups. So rather than
say there is a difference between groups there is
a difference between two hamsters and the rest of
their group. Why there is a difference with these
Golden Hamster
12
two hamsters I'm not sure.
This study further supports and extends preference
tests done by experimenters such as Wecker (1963)
and Klopfer and Hallman (1965). This study supports
them by showing that animals do in fact prefer one
environment over another regardless of experience.
This study extends previous studies by showing that
these preferences do remain over time even for numerous
generations raised away from their natural environment.
My results apply to the golden hamster only. Whether
it applies to other species would be a question for
further study. Therefore it follows that this
preference in the golden hamster for its natural
environment follows Darwin's (1859) theory of natural
selection. This preference has not been altered by
laboratory experience because it is still advantageous
to the survival of the species. In what way it is
advantageous could be the next step undertaken in
the way of research.
I do know that after observing the hamsters in
the Natural Environment group there are some traits
that were displayed that may explain traits present
Golden Hamster
13
in today's hamsters found in the Pet-Store Environment.
The main trait is burrowing. The hamsters in the
Natural Environment burrowed down into the soil
where when they were sleeping I could not observe
them. This trait is seen in hamsters raised in
a woodchip environment. They dig through the woodchips
almost as if they were burrowing and also when they
sleep many of them bury themselves under a pile
of woodchips.
Another point of interest I noted was escape
behaviors in both groups. I had no escapees from
the Natural Environment group yet I did have escapees
from the Laboratory Environment group. This may
have been coincidence but I did notice that the
hamsters in the Laboratory Environment would try
to climb the glass wallls and also try to chew through
the barricades I had set up dividing the sections.
I rarely observed this in the Natural Environment
group. The reason for this could be that since the
hamster still prefers its natural environment it
could be better adapted to its natural environment
thus have no need to escape but this is purely
Golden Hamster
14
speculative.
There are other possible explaAnations besides
a genetic hypothesis as to why the golden hamster
prefers its natural environment. One explaination
could be odor. Odor preference test studies done
by Brown and Willner (1983), Brown (1982), and Brown
and Elrick (1983) show that rats have preferences
for different odors. For example, Brown and Willner
(1983) showed that rats show a strong preference for
maternal odors and a strong aversion to peppermint
odors. If odor preferences hold true for the golden
hamster also, there could be the possibility that
the hamster prefers the odor of the natural environment
over the odor of the laboratory environment. To
determine if this was true or not further testing
would have to be done.
Another possible explanation could be there
is more for the hamster to do in the natural
environment. For example, if the hamster spends time
in the natural environment side burrowing then it
is being kept active thus it has no need to go to
the other side. There is the possibility that there
Golden Hamster
15
is much less for the hamster to do on the Laboratory
Environment side. If this is the case then the
two sides should be equalled out as to activéty
purposes and the experiment redone.
In conclusion, I would like to propose possible
studies for further research in this area. Studying
other animals that have been out of the wild for
many generations is one possibility to expand on
this study. Also testing for the control of such
things as activities or odors in the different
environments would increase the validity of this
study. Finally, this experiment could be repeated
using variations such as using older hamsters,
increasing experience time, or increasing the number
of test days.
Golden Hamster
16
References
Alcock, J. (1984). Animal behavior: An evolutionary
approach. Sunderland: Sinauer Associates.
Brown, R. (1982). Preferences of pre- and postweanling long-evans rats for nest odors. Physiology
and Behavior, 29(5), 865-874.
Brown, R. and Elrick, D. (1982). Preferences of
pre-weanling tong-kvans rats for anal excreta
of adult males and females. Physiology and Behavior,
30, 567-571.
Brown, R. and Willner, J. (1983). Establishing an
"affective scale" for odor preferences fo infant
rats. Behavioral and Neural Biology, 38, 251-260.
Darwin, C. (1859). On the origin of species by
means of natural selection. New York: D. Appleton.
Klopfer, P.H. (1969). Habitats and territories:
A study of the use of space by animals. New
York: Basic Books.
Klopfer, P.H., and Hailman, J.P. (1965). Habitat
selections in birds. In D.S. Lehrman, R.A. Hinde,
& E. Shaw (eds.), Advances in the study of behavior
(pp. 279-3030). New York: Academic Press.
Golden Hamster
17
Roberts, M.F. (1974). Teddy bear hamsters. Toronto:
Clarke, Irwin, & Company.
Wecker, S.C. (1963). The role of early experience
in habitat selection by the prairie deer mouse.
Ecology, 33, 307-325.
Zucker, I. and Stephan, F.K. (1973). Light-dark
rhythms in hamster eating, drinking, and locomotor
behaviors. Physiology and Behavior, 11, 239-250.
Golden Hamster
18
Figure Caption
Figure 1. The mean percentage time spent on each
side of the preference test box for the Natural
Environment group and the Laboratory group.
pralsrsnts tsat
natural
laboratory
natural
laboratory
environment
Golden Hamster
19
Figure Caption
Figure 2. The percentage of time spent on each side
of the preference test box each day for each hamster
in both the Natural Environment group and the Laboratory
Environment group.
Laboratory Environment Group
2
3
day
Natural Environment Group
2
day
3