Sociality and Social Behaviour (Part 2)

1. Sociality and Social Behaviour(Part 2)

2. Reciprocity - incur a cost now in anticipation of receiving a benefit later Altruism by non-relatives Modelling - use Game Theory - John Nash

3. Prisoner’s Dilemma Altruism by non-relatives 2 prisoners - caught and jailed for a petty crime - suspected of having committed a more serious crime

4. Prisoner’s Dilemma Altruism by non-relatives Each prisoner (player) has a choice cooperate - deny all knowledge of the serious crime defect - accuse the other of the more serious crime Reward for defecting - forgiven minor crime

5. Prisoner’s Dilemma Altruism by non-relatives Each strategy has a payoff Payoff depends on behaviour of the opponent 1. Both cooperate - both get a reward - R 2. Both defect - both get punished - P 3. One cooperates & one defects - defector set free - T (temptation payoff) - cooperator jailed - S (sucker’s payoff)

6. Prisoner’s Dilemma Altruism by non-relatives This relationship of payoffs must hold T > R > P > S Temptation > Reward > Punishment > Sucker’s

7. Maximum sentence - 12 years (10 for major, 2 for minor) What are the years saved by each strategy? Altruism by non-relatives Player B Plays first Cooperate Defect Player A S = 0 R = 10 Cooperate T = 12 P = 2 Defect

8. Prisoner’s Dilemma How should they behave? Altruism by non-relatives -should defect - always saves something Player A • if B cooperates - T > R -if B defects - P > S If both defect do worse than if they cooperate R > P Player B

9. Prisoner’s Dilemma How should they behave? Altruism by non-relatives After a number of simulations with more than one move, Best strategy is a tit-for-tat -cooperate on first move and then do what opponent did on previous move

10. Prisoner’s Dilemma Benefits of tit-for-tat Altruism by non-relatives Initially cooperative Quick to retaliate Quick to forgive

11. Does this work in nature? Altruism Kin Selection Reciprocity

12. Kin Selection - in mate acquisition Altruism Wild turkeys - male progeny of a single brood - group for life -dominance hierarchy - only dominant male mates

13. Kin Selection - in mate acquisition Altruism Reproductive success of non-mating males -realized through RS of brother How? If brother mates with four females -non-maters RS = 4 x relatedness x .5 (to account for female’s contribution) = 4 x 0.5 x 0.5 = 1.0

14. Reciprocity - in mate acquisition Altruism Long tailed manakins

15. Reciprocity - in mate acquisition Altruism Long tailed manakins - only dominant male mates Courtship dance Subordinate Dominant

16. Reciprocity - in mate acquisition Altruism Does subordinate male assume role of dominant? predicted • • Copulations per hour: New alpha male • observed • • • • • Copulations per hour: previous alpha male

17. Reciprocity - in mate acquisition Altruism Why have 2 males? - females are attracted to 2-male courtship groups

18. Reciprocity - in predator detection Altruism Meerkats - sentinels

19. Reciprocity - in predator detection Altruism Meerkats - sentinels -forage in groups - not related -every so often - one animal stands to look for predators -sentinel warns of approaching predator

20. Reciprocity - in predator detection Altruism Meerkats - sentinels This behaviour is adaptive if: Chance of being preyed on while acting as a sentinel Survivorship while others are sentinels <

21. Reciprocity - in predator detection Altruism But is this really reciprocity? Alternative hypothesis (selfish): “Sentinels” are really just animals who have finished feeding and are looking for predators to protect themselves.

22. But is this really reciprocity? Some predictions from reciprocity hypothesis: Altruism Prediction Observation Regular rotation of sentinel duty Sentinel duty appears to be haphazard Sentinel duty has risk of succumbing to predator Sentinels are usually closer to an escape burrow Less time is spent in predator detection in groups No difference in sentinel time when solitary