Leslie Samuel
Take-Home Exam
Animal Behavior
1. During migration, navigation is a critical ability. Describe in detail, one way
navigation can be accomplished. What are its limitations and what are its
advantages. Also describe at least one way that this form of navigation has
been studied experimentally.
Navigation can be accomplished by the use of the mechanism known as piloting. This
mechanism is based on the organism’s relationship to distant fixed cues. An
advantage to this mechanism is that it does not require a compass. A limitation is that
if those landmarks are moved (e.g. during a storm), the organism can get disoriented.
Niko Tinbergen tested this by moving the objects closest to the nest of a female
digger wasp, which was thought to use the location of landmarks to recall the location
of its nest. When he did this, the female digger wasp looked for its nest where the
moved objects were.
2. How would you answer (as a biologist) the following question from a 4 year
old: “Why is that bird singing?”
Singing in birds plays a big part in how birds recognize each other. Boy birds try to be
with girl birds of the same kind and girl birds try to be with boy birds of the same kind,
and one way in which they recognize that they are of the same kind is by singing. Also,
mommy and daddy birds use the song of the baby birds to find and recognize them.
Birds also sing to defend their homes (territories). When they sing, it’s kind of saying,
this is my home, so other birds stay away!
3. Contrast and compare the two major hypotheses to explain dispersal from
the natal site. Devise an experiment that you feel would help distinguish the
two. Be specific.
One hypothesis is that of inbreeding avoidance. This hypothesis says that dispersal from
the natal site happens to avoid mating between closely related individuals. When closely
related individuals mate, it results in reduced reproductive success and reduced survival
of offspring. The other hypothesis is the intraspecific competition hypothesis. This states
that dispersal happens because of resource limitations.
One way of testing this is by limiting resources more than they normally are and see if
this would increase or speed up dispersal from the natal site. Then you can increase the
available resources and see if this would decrease the amount of dispersal from the natal
site. As a control group you can keep the amount of resources available as they normally
are. If changing the amount of available resources does not affect dispersal, then
intraspecific competition can be ruled out.
4. Why have all of these optimal foraging strategies? Why not just pick your
favorite prey item, chase it down and have a feast?
Because an animal must maximize its inclusive fitness. In order to do this, it must find
the best way of doing things depending on the circumstances/conditions it finds itself in.
In some cases, chasing down your favorite prey item might be a good idea. However, in
other situations, this might not be the best idea. E.g. if it takes too much energy to chase
down the food, it might be a smarter idea to set a trap and let the food come to you. Also,
the animal is limited to what is available. If your favorite prey item is not available, it has
to find something else.
5. Using specific examples explain how having close relatives (excluding
parents) can be an advantage to your survival or in other instances could
clearly be a detriment to your survival?
Young spotted hyenas fight vigorously while in the den, often resulting in one sibling
killing the other. This is known as siblicide and is one example of how having close
relatives can be a disadvantage. An advantage of having close relatives is that it gives
animals the opportunity to pass on their genes either by improving the chances of success
of their offspring or by helping other relatives. This example is seen in hyenas, where
communal nesting between relatives happen.
6. Using two examples, what is meant by “Sperm competition”? What does it
accomplish? Design an experiment to test one of your ideas.
First-male guinea pigs deposit copulatory plugs into females. First-male Fruit flies
transfer antiaphrodisiac substances to female fruit flies when they mate with them. In
both of these examples, these things are done to reduce the chance of sperm displacement
by other males. On way in which the second example can be tested is by isolating the
antiaphrodisiac substance and transferring it to a virgin female of the species and see
whether it would affect its mating with males. Also, you can remove the organ/gland
known to produce the antiaphrodisiac substance in the male, allow them to mate with a
female and see how it affects whether or not the chance of sperm displacement by other
males increases. Of course, as a control group you would have to have a group that
allows the male to mate with the female, without removing the gland and without
artificially applying the substance to the female.
7. Contrast and compare Polygyny and polyandry. Use examples of each to
show the advantage that each may have.
Polygyny and polyandry are 2 different kinds of polygamy, which is a mating system in
which a single individual mates with more than one individual of the opposite sex. In
polygyny, one male mates with more than one female at a time and in polyandry, one
female mates with more than 1 male at a time. An example of polygyny can be seen in
sage grouse. One male mates with several female and they occupy the same territory. The
male defends the territory and the female benefits from being in a well-defended territory.
An example of polyandry is seen in female wattled jacanas (tropical shorebirds). The
female mates with a male, and the male is left to incubate the young, while the female
goes and mates with other males. This is beneficial to the females because her
reproductive success is enhanced by having lots of males raising her young for her.
8. We learned about Dark-eyed Juncos during our ethogram presentations.
They tend to live in flocks in the winter. List possible benefits and costs of
such a social behavior. Design an experiment to test one of your suggestions.
Benefits:
Easier to locate and procure food
Resource defense against conspecifics or competing species
Richer learning environment
Aiding (or receiving aid from) offspring or other relatives
Costs:
Increased competition for resources
Increased chance of spread of disease and parasites
Interference with reproduction, such as killing of young by nonparents