Sociality and the adaptive value of helpful behavior

1. Sociality and the adaptive value of helpful behavior ZOL 313 June 17, 2008

2. Sociality and the adaptive value of helpful behavior • Objectives: • Become familiar with some of the costs and benefits of social living. • Understand the differences between cooperation, reciprocity, and altruism and be able to generate hypotheses and predictions. • Understand why altruism usually occurs between kin and be able to use Hamilton’s rule to calculate whether altruistic behaviors are adaptive. ZOL 313 June 17, 2008

3. Costs and benefits of social living Foraging Costs: Benefits:

4. Costs and benefits of social living Predation Costs: Benefits:

5. Costs and benefits of social living Disease/parasitism Costs: Benefits:

6. Costs and benefits of social living Mating Costs: Benefits:

7. Costs and benefits of social living Parental Care Costs: Benefits: Prediction: Parasitic coot eggs that look less like their host’s eggs will be more likely to be rejected.

8. The adaptive value of helpful behavior Types of social interactions between animals Donor Recipient Selfish behavior Spiteful behavior Mutualism/ Cooperation Reciprocity Altruism

9. The adaptive value of helpful behavior: Cooperation: A mutually beneficial interaction between two members of the same species. Example: Example: Bubble net hunting by humpback whales

10. The adaptive value of helpful behavior: Cooperation: A mutually beneficial interaction between two members of the same species. Example: Cooperative courtship in the long-tailed manakin The beta male helps the alpha male display to receptive females but NEVER gets to mate with any of them. How can this be cooperation? http://youtube.com/watch?v=-_IYBJjnw2U&feature=related

11. The adaptive value of helpful behavior Cooperation: A mutually beneficial interaction between two members of the same species. Example: Cooperation among competitors in the lazuli bunting Bright, dominant males allow dull competitors to claim high quality territories next to them but drive away intermediate colored males. Benefit to bright males: Benefit to dull males:

12. The adaptive value of helpful behavior Reciprocity: The recipient of a helpful action repays the donor later in time. Problem: Vulnerable to cheating. Why should the recipient repay the donor? Game theory shows that reciprocity is more likely to occur when

13. The adaptive value of helpful behavior Reciprocity: The recipient of a helpful action repays the donor later in time. Example:

14. The adaptive value of helpful behavior Reciprocity: The recipient of a helpful action repays the donor later in time. Example: Meerkats forage in groups. Sometimes an individual will stop foraging and act as a “sentinel”, watching for predators and giving an alarm. Hypothesis 1: Reciprocity. Meerkat sentinels help others at a personal cost now because Hypothesis 2: Personal Safety. Meerkat sentinels are the animals that are sated, so they obtain

15. The adaptive value of helpful behavior Reciprocity: The recipient of a helpful action repays the donor later in time. Sentinels are not more likely to be preyed on than foragers. Meerkats that are given food supplements spend more time as sentinels.

16. The adaptive value of helpful behavior Reciprocity: The recipient of a helpful action repays the donor later in time. Prediction:

17. The adaptive value of helpful behavior Altruism: Helpful behavior that lowers the direct fitness of the donor and raises the fitness of the recipient Example: Belding’s ground squirrels alarm calls 1. Squirrels that alarm call are more likely to be killed by predators than non-callers. 2. The probability that an individual will alarm call is not correlated with familiarity/length of association with recipient. 3. Females with kin (sisters, aunts, cousins) nearby Most (non-human) altruistic behaviors that we know of are performed toward relatives. Is this really altruism?

18. The adaptive value of helpful behavior Altruism: Helpful behavior that lowers the direct fitness of the donor and raises the fitness of the recipient 2 Inclusive fitness= C=cost to donor B=benefit to receiver R=relatedness (between donor and recipient) Hamilton’s Rule: R x B > C

19. The adaptive value of helpful behavior Altruism: Helpful behavior that lowers the direct fitness of the donor and raises the fitness of the recipient Example: A Belding’s ground squirrel who gives alarm calls will have 2 fewer offspring over her lifetime than if she never called. However, by calling when she sees a predator she will save the lives of 5 of her sisters. Is this “altruistic” behavior adaptive? R= B= C= 2 C=cost to donor B=benefit to receiver R=relatedness (between donor and recipient) Hamilton’s Rule: R x B > C

20. The adaptive value of helpful behavior Cooperative breeding: “altruistic” helpers increase their inclusive fitness Prediction:

21. The adaptive value of helpful behavior Cooperative breeding: “altruistic” helpers increase their inclusive fitness In pied kingfishers, some yearling males are not able to find a mate. Options: Primary helper: Help parents breed Secondary helper: Help non-related birds breed Delay: Wait until next year Prediction:

22. The adaptive value of helpful behavior Cooperative breeding: “altruistic” helpers increase their inclusive fitness Example: Cooperatively breeding paper wasps. Subordinate females help care for the brood and defend the nest against predators. One dominant female monopolizes the egg laying. Based on what you know about altruism, when might it be adaptive for subordinate females to help instead of trying to reproduce on their own?

23. The adaptive value of helpful behavior How can cooperative breeding among non-relatives be adaptive? Transactional Theory Dominants and subordinates “negotiate” their reproductive rights within the group. A dominant might allow a non-relative subordinate a small amount of reproduction to secure her help. Prediction: