Animale Ecology (Zoology 441)
Practice Questions --  behavioral ecology: group living, mating systems
 

1. Distinguish between the hypotheses for an advantage to group living that were tested in the study of starlings versus the study of pigeons.  Are these hypotheses mutually exclusive (in other words, if one is true for a species does that mean the other one isn't?)
2. What is the "selfish herd phenomenon"? What is evidence for this phenomenon?
3. Why does the proposed advantage to group living that is based on finding food apply only to species whose food resources occur in patches?
4. For each of the following, discuss which of the two species would be more likely to forage (look for food) in groups; relate your discussion to the proposed benefits and costs to group living discussed in lecture. (a) a species of finch that occurs on islands where there are no finch predators and a species of finch that occurs on the mainland where there are many predators.  (b) a species of fish that occurs in stagnant water with extremely low visibility and a species of fish that occurs in clear water with high visibility.  (c) a species of mammal that lives in an area with abundant, evenly distributed food and a species of mammal with scarce, evenly distributed food.  Both species suffer from moderate levels of predation.  (d) a species of bird that feeds on berries that grow on bushes; each berry bush has hundreds of berries and is separated from other berry bushes by many non-berry bushes, and a species of bird that feeds on seeds that are evenly distributed in the environment
5. You observe that a species of fish occurs in schools (groups).  Give three different hypotheses, all related to predation, that could explain why these fish occur in schools.  Give a prediction of each hypothesis.
6. In cooperatively breeding birds and mammals, what are three ways in which helpers have been shown to improve reproduction of breeders?
7. Explain two different reasons, one related to habitat and one related to mates, that helpers don't breed
8. You observe two species of woodpecker.  In one species, breeding and survival depend on modifications of the habitat that the woodpeckers make over a period of several years.  In the other, woodpeckers do not modify their habitat.  In which would you expect cooperative breeding to be more likely?  Fully explain why.
9. Suppose you wanted to test the hypothesis that dispersal is constrained by a shortage of territories in acorn woodpeckers.  Propose two different methods for testing this hypothesis, and state what each predicts.  Would either or both methods help rule out an alternative hypothesis that dispersal is constrained by lack of mates?  Explain.
10. Describe three different categories of cooperative breeding.  Which is most common?
11. Give three different hypotheses that explain ways in which helpers in cooperative breeding systems could improve their future reproduction.  How could you test each of these hypotheses?  What have previous studies indicated about each of these hypotheses?  Suppose you tested them and found all of them to be false.  What are two other possible hypotheses that could explain why helpers help (given that they have not dispersed to breed).
12. What is meant by the environmental potential for polygyny? How is it related to the "spaced out female" effect?
13. Caciques are tropical birds that have long, hanging nests.  These nests keep nestlings safe from most predators, except for monkeys -- monkeys have long arms and can reach into the nests to eat eggs or nestlings.  Monkeys spend their time in the canopy of the tropical rainforest.  There are a few trees in the forest whose crowns are not continuous with the canopy, so monkeys do not visit these trees.  Most trees are continuous with the canopy and visited by monkeys.  Would you expect the caciques to be monogamous or polygynous?  Explain why, with reference to the environmental potential for polygyny.  How does your answer depend on whether the young require care of both parents for survival?
14. You observe that a species is monogamous.  Give two different hypotheses that could explain why it is monogamous.  What would each of these predict?
15. Female willow ptarmigans (a kind of bird) defend large territories from other females.  Would you expect this species to be monogamous or polygynous?  Why?
16. Some species of Peromyscus (deermouse) are monogamous; others are polygynous.  Give two possible hypotheses that could explain the difference in mating system.  How could you test these hypotheses?
17. Some bird species have high levels of nest predation such that a nest cannot be left unattended without having a very high chance that a predator will eat the eggs or young.  Other bird species have much lower levels of nest predation.  In with of these situations would you expect more polygyny and in which more monogamy? Why?
18. Most mammals are polygynous; most birds are monogamous.  Develop a plausible explanation for the difference based on the hypotheses for different mating systems discussed in lecture (hint: in which are young more likely to require food from both parents for survival?  Why, and how does this impact the mating system that is expected?)
19. In what situations is polyandry predicted?
20. Why do we have to distinguish between the social mating system and the genetic mating system of species?