Biology 441. Animal Behavior KEY
Final Examination, 14 December 1994

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40 pts. 1. Define and provide an example of each of the following (4 pts. each):

a. lek

a traditional display site where males gather to defend small territories that lack resources useful to females, which nevertheless visit the site to make.

e.g. Uganda kob, sage grouse

b. parental investment

any investment by a parent in an individual offspring that increases the offspring's chance of surviving while decreasing the parent's ability to invest in other offspring.

e.g. female produces milk, invests a large amount in an egg

c. parent-offspring conflict

parents and offspring are likely to disagree about how important survival of that one offspring is relative to alternate options available to the parents

d. epigamic selection

process which acts on those characters in males which influence a female's choice

e.g. evolution of male courtship displays

e. evolutionarily stable strategy

a strategy that cannot be replaced by an alternative by the action of natural selection, ie., fitness of individuals adopting that strategy is equal or higher than the fitness of individuals adopting other strategies.

e.g. jacks vs. Hooknoses, tending in bighorn sheep

f. resource defense polyandry

females defend territories and provide clutches for males settling on their territories. Some females are successful, some are not.

e.g. spotted sandpipers, humans in Tibet

g. frequency dependent selection

a form of natural selection in which the fitness of an individual is dependent upon the frequency of its phenotype in a population with 2 or more discrete phenotypic alternatives

e.g. daring vs cautious mobbers in gulls, marine isopod sex ration differing from 50:50

h. conditional ESS

a set of rules that enables individuals to exhibit different tactics under different environmental conditions; the capacity to be behaviorally flexible.

e.g. coursing and blocking in bighorn sheep

i. sperm competition

competition among the sperm of 2 or more males for egg fertilization.

e.g. black-winged damselfly scrub-brush; dunnocks

j. cooperative breeding

non-breeding individuals aid in raising young that are not their own.

e.g. Florida scrub jay, Green woodhoopoe, White-fronted bee eaters

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(20 pts.) 2. Sometimes Mexican free-tailed bat mothers nurse offspring other than their own and sometimes vampire bats share their blood meals with others within the roost. Separately evaluate the direct and indirect costs and benefits to both donors and recipients in these two examples and explain why these behaviors have evolved.

Free-tailed bats:

• Direct cost to donor -- loss of milk
• Direct cost to recipient -- loss of milk
• Indrect cost to donor -- loss of milk to own young
• Indirect cost to recipient -- unclear
• Direct benefit to donor -- may help related young
• Direct benefit to recipient -- milk
• Indirect benefit to donor -- others may do the same for her offspring
• Indirect benefit to recipient -- others may do the same as mom
  

• Direct costs: low because individuals share "surplus"
• Kin are helped indirectly
• Non-kin are possibly tit-for-tat cooperating
  

(20 pts.) 3. Define and graphically represent the polygyny threshold model. Does it adequately explain polygyny in the yellow-bellied marmot? in 19th century Mormon societies? Explain why or why not for both examples.

The polygyny threshold model suggests that if variability in habitat quality is high, unmated females should pair with already mated males in high quality territories. This should be the case if females can expect higher success with mated males than by mating with an unmated male on a poorer quality territory.

Yellow-bellied marmots: NO because polygynous females have lower reproductive success than monogamous females. Also, the reproductive success of a female is lower in larger harems.

Mormons: YES because female reproductive success is independent of harem size.

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(20 pts.) 4. Outline the types of mating systems that can be found within even a single population of the dunnock (hedge sparrow) and explain why each type occurs.

Females arrive first in the spring and establish breeding territories. If a male is able to successfully defend one female's territory and exclude all other males, MONOGAMY will result. In some instances resource aboundance is high so female territories are small and a male may be able to successfully defend and exclude all other males from the territories of two breeding females, resulting in POLYGYNY. If a monogamous male is unable to exclude an intruding male, the female will court the intruder and copulate with him, resulting in POLYANDRY (males who copulate with a particular female will help feed her young). POLYGYNANDRY can result if two adjacent females are able to successfully solicit copulations from each other's mate or if an intruding male successfully establishes alliances with the females on a polygynous male's territory.

(20 pts.) 5. In some fish species individuals change sex from male to female and in others individuals change sex from female to male. Explain why each of these types of sex change occurs.

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(20 pts.) 6. If you killed and collected all 500 wasps that were in a paper wasp nest in early summer in the Fairbanks area, how many reproductive males and females would you find? How many nonreproductive males?, nonreproductive females? Show, using appropriate diagrams, what the coefficients of relatedness would be within and between the types of individuals present at that time.

ONE REPRODUCTIVE FEMALE (QUEEN) AND NO REPRODUCTIVE MALES (DRONES)--DRONES DIE AFTER MATING THE PREVIOUS FALL.

499 NONREPRODUCTIVE FEMALES (WORKERS) AND NO NON-REPRODUCTIVE MALES (NO SUCH THING IN THE HYMENOPTERA)

Worker is diploid and recieves half of her genes from her mother; therefore worker-queen r = 0.5.

If the queen mates only once all the workers are full sisters. Workers recieve half of their genes from their mother and there is a 50% chance that they receive a particular allele from the mother. Workers also receive half of their genes from their father , but tsince the father is haploid there is a 100% chance they will both receive an allele present in the father. Therefore, worker-worker r=(0.5*0.5)+(0.5*1)=0.75.

(10 pts.) 7. In Chapter 15 (Caring for Offspring) Alcock states that paternal care can evolve within a species even if certainty of paternity is low. I disagree, and I doubt that paternal care would either evolve or persist in a population or species unless the probability of paternity is high. Discuss which of these positions is more likely using information on the variability in patterns of paternal care in different human societies.

In most human societies cuckoldry is considered a crime against the husband, and cuckolded husbands are likely to divorce their wives and provide no care for offspring. On average, step-fathers are much more likely to abuse step-children than fathers are likely to abuse their own children. In South Sea Island cultures, where certainty of paternity is low, males tend to care for their sitsters' offspring rather than their wife's offspring. All of these examples suggest that paternal investment is reduced or curtailed when certainty of paternity is low.

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(25 pts.) 8. Earlier in the semester I discussed Susan Smith's findings that some adult Rufous-crowned Sparrows are unable to become breeders but are able to live on the breeding territories of other individuals, forming an "underworld" society. None of these nonbreeders helps the breeding pair. In contrast, young nonbreeding adult Florida Scrub Jays stay on their natal territory and help their parents defend the territory and raise the young, and young male Pied Kingfishers that cannot find a territory or mate either stay on their natal territory and help their parents, emigrate from the natal territory and help an unrelated pair raise its young, or become floaters. First, explain why young male and female scrub jays stay at home and help. Second, what are the relative costs and benefits to male Pied Kingfishers who help at the natal nest, the nest of nonrelatives, or disperse but do not help anywhere? Third, what are the possible reasons why nonbreeding adult rufous-crowned sparrows do not stay on their natal territories and help their parents or help the pair on the territories where they are living?

SCRUB JAY (10 Points)

Males increase indirect fitness by helping to raise related offspring, the probability of survival by raising subordinates who are more likely to suffer predation, and the probability of future breeding because territory size increases as group size increases. If the territory becomes large enough the male may be able to "bud off" a portion of his father's territory for his own. A male also may be able to become the breeder on the natal territory if the father dies or the breeder on a nearby territory if the male there dies and has no male helpers.

Females increase indirect fitness by helping to raise related offspring and their probability of surviving until a vacancy elsewhere occurs. (Females do not breed on the natal territory)

PIED KINGFISHER (10 Points)

Females are in short usupply because of higher female mortality and can find breeding vacancies; therefore, females do not help. Males may help at the natal nest ("primary helpers"), gaining indrect fitness benefits by raising related offspring but suffering direct fitness costs because primary helpers have relatively low survivorship to the next breeding season. Males may leave their natal territory and become secondary helpers at the nest of an unrelated pair. They assist somewhat, decreasing their fitness relative to the breeding pair in the first year, but their survivorship to the next breeding season is high and they have a high likelihood of becoming the breeding male if the male on that territory dies. Males also may become "delayers" (floaters), leaving the natal territory and not helping elsewhere. These males have none of the indirect fitness gains enjoyed by primary helpers or potential future direct fitness gains enjoed by secondary helpers and thus have the lowest fitness.

RUFOUS-CROWNED SPARROW (5 points)

There is no clear answer why individuals would be floaters rather than adopting strategies similar to the primary or secondary helping strategies of the pied kingfisher. Perhaps they would compete too much with their parents and reduce their parents' subsequent nesting success if they stayed at home. Similarly, perhaps they would not be tolerated near the nest of nonrelatives if their presence on territories of nonrelatives reduces the ability of nonrelatives to raise young. Whatever the reason, it appears that floating on established territories results in higher fitness than any type of cooperative strategy.

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