Study questions Living in groups 1. What are three costs and three benefits of living in groups? 2. What is the dilution effect? What is a key assumption of the dilution effect hypothesis? What is a biological example? 3. What is meant by predator swamping? How is this achieved? What is an example? 4. Why do mayflies all emerge at the same time? Does mating play a role? 5. Given one example of a temporal dilution effect vs a spatial dilution effect. 6. What is meant by the selfish herd? What kinds of behaviors does this explain? What are the tradeoffs of a selfish herd effect? 7. What evidence supports the idea that risk of attack increases with a greater domain of danger? 8. What mechanisms might give rise to predator confusion? How has the idea of predator confusion been tested? 9. How might animals reduce predation through communal defense? How could you test if there is communal defense? 10. What evidence supports the idea that groups might have increased vigilance for predators? Why might individual vigilance levels go down? What is an example of individual vigilance decreasing with group size? 11. Describe the potential for cheating in terms of individual vigilance for predators when the individual is in a group. Why might cheating not be a good strategy? Give a biological example of this. 12. Is sentinel behavior likely to have been selected because of benefits to the group or because of benefits to the individual? What factors would suggest that it arises from selfish individual behavior? Give a biological example. 13. Why do sentinels sing songs while on guard? What are the costs and what are the benefits? 14. What are the four different ways in which being part of a group can reduce predation? How are they different? How are they similar? 15. What are two ways in which being in a group can improve foraging? Give an example of each reason. What is a potential tradeoff of foraging in the group?
16. How might groups act as information centers for improving foraging? What ecological conditions might select for information transfer? What are two ways in which information may be transferred? 17. How do we know that ravens transfer information about where to forage? Why might this have been selected for? 18. Why might groups of predators be better at prey capture? Give an example. 19. Describe the experiment where guppies were moved between streams with different predation pressures. How does this show that grouping behavior may evolve quickly? Why might grouping behavior be selected against? Why might it be selected for? 20. What are two costs of group living? 21. Why might there be an optimal group size for an individual? Why might this optimal group size not be stable? 22. What factors does reproductive skew theory consider? Why might reproductive skew arise within a group? How do coral gobies demonstrate reproductive skew? What are the tradeoffs of group living of a coral goby? Evolution of Social Behavior 1. What are the four types of social interactions between two individuals? How do these interactions affect the reproductive success of the individuals? Which interactions can easily be explained by natural selection? Which of the interactions are more difficult to be explained by natural selection? 2. What is reciprocal altruism and reciprocity? What is a central problem that can prevent reciprocal altruism from evolving? 3. What is the scenario of the Prisoner s Dilemma? In order to be the Prisoner s Dilemma, what do the payoffs have to be? Why is it useful to study the Prisoner s Dilemma model? 4. What is the dilemma part of the Prisoner s Dilemma? What is the best move when playing one round of the Prisoner s Dilemma? In this situation, do you predict that cooperation will evolve? How does this inform us about one of the requirements that is needed for reciprocal altruism? 5. What is the iterated Prisoner s Dilemma? Why is the strategy Tit for Tat a successful strategy for playing this game? Why can Generous Tit for Tat sometime beat the Tit for Tat strategy? (Side question just to think on: Do you find it is interesting that the
philosophy of Tit for Tat/The Golden Rule is a very common thought in widely diverse human cultures? Why do you think this is?) 6. Why is game theory important for studying the evolution of behaviors? What is game theory? 7. What is an ESS? What is an ES-state? Are the strategies of the Prisoner s Dilemma an ESS? What does it mean for a strategies to be mixed or pure? 8. How are vampire bats an example of reciprocal altruism? How do they meet three requirements that are needed for reciprocal altruism to evolve? What experiments were done to show this? 9. How might olive baboons exhibit reciprocal altruism? Why do you think this cooperative mating strategy evolved? Bonus Material: Ever wonder what it is like to do field work for behavioral ecology? Want to know more about sharing behavior in vampire bats? Check out this interview with Gerald Wilkenson who talks about his work on reciprocal altruism! http://www.radiolab.org/story/105440-blood-buddies/ Were you interested in Alxerod s computer tournament, which discovered that tit for tat is a good strategy? Here is an interview with him, describing this classic work. http://www.radiolab.org/story/104010-one-good-deed-deserves-another/ Kin Selection 1. What is Hamilton s theory about the goal of reproduction in terms of evolution? How does personal reproduction relate to this? How does helping relatives relate to this? 2. What is Hamilton s rule? What are each of the parts of the equation and how are they measured? Why is the r term so important for the equation in terms of understanding altruism? How does Hamilton s equation predict how altruistic behaviors should vary across individuals. 3. How many brothers, cousins, or half brothers would you give your life for if you were thinking sttrictly in terms of kin selection? Would you give your life for your aunt s second cousin s daughter? 4. You should be able to calculate the coefficient of relatedness for different family relationships such as the ones we went over in class. 5. What is inclusive fitness? What are the two parts of inclusive fitness? What do individuals seek to do to their inclusive fitness? How does this relate to altruism?
6. Describe an example in which an individual maximizes its inclusive fitness via kin selection (i.e. the indirect component of inclusive fitness). How has the individual s direct fitness been affected? 7. Why do pied kingfishers become helpers at the nest? What other behavioral choices do they have? How does helping affect their direct fitness? How does it affect their indirect fitness? Do other strategies have higher direct fitness? 13. Do bee-eater one year olds help any individuals at the nest? Where do they direct their helping? What is the cost of this? What is the benefit to the birds being helped? What is the benefit to the helper? Why would father bee-eaters harass their sons and prevent them from nesting? How is this an example of a parent-offspring conflict? 14. Describe the two types of alarm calls in Belding s ground squirrels. Which is a selfish call? Why? Which is an altruistic call? Why? Why are more alarm calls given by females? How do they bias their alarm calling? How else do they cooperate with each other? 15. Female Belding s Ground squirrels do not disperse, but males do disperse. Jpw dp the sexes differ in alarm calling.? Describe female trilling alarm calling behavior and why it suggests that interactions among kin may increase inclusive fitness. Address all parts of Hamilton s equation in your answer. Why might males behave differently? 16. Why should any animal avoid altruism to non-kin? Why should coots avoid altruism to non-kin? How do coots avoid altruistic behavior to parasitic egg layers? What are the costs to them should they fail to reject a parasitic egg? 17. What are the proximate and ultimate causes of coots rejecting parasitic eggs? Kin Recognition 1. Compare and contrast the three possible ways of recognizing kin. Does the theory of kin selection require kin recognition? 2. What are the three characteristics of a green beard gene? How does this sort of gene explain the evolution of altruistic behaviors? Why are greenbeard genes unlikely to be common? 3. How does the Gp-9 gene in meet the three requirements of a green beard gene? What is the proximate mechanism for recognition? 4. How might direct genetic discrimination of kin occur? Describe an example. 5. How do slime molds exhibit altruistic behavior? How is this explained by kin selection? How is kin recognition involved?
6. How might animals use simple environmental cues to recognize kin? What kinds of problems might using environmental cues lead to in terms of whether kin are recognized or not? Why might these problems be tolerated? 7. What form of kin recognition is imprinting? 8. Describe the experiments on Belding s ground squirrels that demonstrated kin recognition. What was the main kin recognition mechanism? What is the evidence for this? What is the other kin recognition mechanism that explains differential aggressive behavior? What is the evidence for this? What is the proximate mechanism for each type of kin recognition? 9. Give two biological examples where two different forms of kin recognition are employed. Describe them. 10. What is needed for kin selection to work even without kin discrimination? What kind of behavioral strategies do we expect when there is not kin discrimination? Are kin discrimination behaviors plastic or canalized? Are strategies without kin discrimination plastic or canalized? 11. What are the cooperators and cheaters in the bacterium Pseudomonas aeruginosa? How does high vs low relatedness affect the proportion of cooperators in the population? Bonus Material In class, we learned about the Prisoner s Dilemma. It turns out that this idea was turned into a game show. Thus contestants faced the dilemma to defect or cooperate. However, they were playing only a single round of the Prisoner s Dilemma, where defect is thought to be the best strategy. This episode is about someone who figured out an ingenious way to win the game. Definitely worth a listen! I promise that you won t be disappointed. http://www.radiolab.org/story/golden-rule/ Bonus Comic People in the class were quite interested in slime molds. Looks like you are well on the way to becoming scientists! (Comic from xkcd)