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to the top.Biology 441. Animal Behavior. Midterm I, Wednesday, 16 October 1996
120 POINTS
(5) WRITE YOUR NAME AT THE TOP OF EACH PAGE
(20) 1. Define and provide an example of each of the following:
a. free-running circadian rhythm a physiological or behavioral periodicity of about 24 hours in the absence of environmental timer (Zeitgeber), e.g., sleep-wake cycle in humans
b. developmental homeostasis capacity for normal expression of behavior in suboptimal environmental conditions (or despite potentially disruptive effects of mutant alleles), e.g., captive infant rhesus monkeys provided with minimal social environments
c. search image a hypothetical mental image of a particular prey
type used by predators of cryptic prey, e.g., specialization on particular
species of potential prey by tits.
d. cognition imagining a solution, e.g., ravens pulling up a rope
to a perch to get reward at end of rope
e. operant conditioning "trial and error" learning; a behavior
that is rewarded becomes performed more frequently and effectively and
one that is punished is performed less frequently; e.g., bar pressing in
pigeons
(15) 2. Briefly describe 3 hypotheses that could account for infanticide
by male hanuman langurs. Provide evidence that either supports or contradicts
each of the hypotheses you have described.
1. Sexual competition infanticidal males may be able to reproduce sooner if mothers of those infants they kill become receptive sooner: examine time between estrous cycles in females who lose infants and those who do not; does infanticide occur when a new male takes over a female group? YES
2. Cannibalism (infants are a food resource): do males consume part or all of the infants they kill? NO EVIDENCE OF CANNIBALISM
3. Social pathology (aberrant behavior that occurs at high densities or in areas of high human disturbance): is infanticide positively correlated with either density or human activity? PROBABLY NOT
4. Decrease competition for resources between own offspring and previous male's offspring. Is offspring survival (fitness) related negatively to group size or is it higher in groups where previous offspring were eliminated after the male takeover? (no data provided)
5. Consequence of elevated stress in male during and just after the
takeover. Does resident male act infanticidal after he successfully defends
his position? (probably not)
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(10) 3. Construct a diagram showing relationships and compute the coefficient
of relatedness between first cousins (r=_(0.5)L). Show the complete diagram
and each step of your calculations.
DIAGRAM
Path through grandmother has 4 links and (0.5)4 = 0.0625
Path through grandfather has 4 links and (0.5)4 = 0.0625
Therefore the sum for the 2 pathways is 0.125.
(20) 4. Describe how you could trick experienced homing pigeons to first
fly due east and then fly due west if you release them 50 km north of the
home loft at noon on bright sunny days. Would this work on a heavily overcast
day? Why or why not?
1. Put test pigeons on an artificial light regime that starts at
midnight and ends just after noon (12L:12D). Keep them there for a few
weeks. Take them out and release them at noon real time. They think "it's
the end of the day, therefore the sun is in the west. Home is to the south;
therefore, I should fly 90 east of the sun." Consequently, they fly
east instead of south.
2. Put the same test pigeons on an artificial light regime that starts
just before noon and ends about midnight (12L:12D). Keep them there for
several weeks. Take them out and release them at noon real time. They think
"it's the start of the day, therefore the sun is in the east. Home
is to the south; therefore, I should fly 90 west of the sun." Consequently,
they fly west instead of south.
3. Neither experiment would work on a heavily overcast day because
they would not be able to sense the position of the sun and would not use
it as a compass. They would use their magnetic compass instead.
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(15) 5. Alcock discusses slug-averse and slug-loving garter snakes.
Generally, coastal garter snakes readily eat banana slugs. Explain how
you would conduct an artificial selection experiment to try to develop
a strain of slug averse snakes from the coastal population. Do you think
that you could succeed? Why or why not?
Within the coastal population there is some variability in odor preferences
and readiness to feed on slugs. If you test newborn naive snakes and select
only those that are towards the averse end of the scale for breeding, you
likely would find that the offspring have higher levels of aversion to
slugs on average. By repeatedly selecting those with the highest measures
of slug aversion as the breeding stock for the next generation, you likely
could produce a strain of slug-averse snakes from the coastal population.
Such an experiment would not succeed if there were no variability within
the coastal population (but there is) or if that variability has no genetic
basis (but it does, as shown in Figs. 17 and 18 on pp. 83-84)
(10) 6. Alcock discusses Bouchard's calculation of heritability, suggesting
that the heritability of IQ in humans is about 0.70. First, what does this
value mean? Second, what is the general procedure for deriving such an
estimate?
First, the heritability value is the proportion of variation among
individuals in IQ scores that can be attributed to genetic differences.
A value of 0.70 means that 70% of the variability in IQ scores (not intelligence!)
can be attributed to genetic differences among the test subjects.
Second, the usual procedure is to examine correlations of IQ scores
of close relatives, e.g., mother-daughter, identical twins. Note that such
relatives often share not only alleles that might affect the trait in question
but also similar or common environments.
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(15) 7. Briefly describe the seasonal changes in testosterone levels
of adult male White-crowned Sparrows breeding in (a) Alaska and (b) Washington.
How do testosterone levels affect reproductive performance during the course
of the breeding season?
(See Alcock Pp. 184-185)
Male white-crowns breeding in Alaska have a single peak in testosterone
levels about the time they mate with females. Male white-crowns breeding
in Washington, where the pair typically raises two or three broods of fledglings,
also show a single peak at the time of mating during the first attempt
of the season. Levels then decline, reaching a much lower plateau (but
higher than in Alaskan white-crowns) until mating during subsequent attempts.
As Alcock discusses, testosterone does not seem to be a key to mating
behavior of males as castrated males will attempt to copulate with females
that solicit copulations. Furthermore, it is not the key to copulations
during second and later breeding attempts of normal males in Washington.
Wingfield and his colleagues have hypothesized that testosterone is important
in priming the aggressive behavior of males so that they can obtain territories
in the spring, and studies of related species have shown that high testosterone
levels interfere with paternal feeding of nestlings.
(10) 8. How does an insectivorous bat flying in complete darkness determine
distance of an obstacle or potential prey item from itself? Explain how
it likely determines the relative speed of a potential prey item that also
is flying.
Distance: time between call emission and echo return (speed of sound
is constant in air).
Relative speed: frequency (or pitch) of returning echo vs. emitted
call. If the frequency of the echo is higher, the bat is closing the distance.
If the frequency is lower the distance between the two is increasing.
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