1. Sociality and Social Behaviour

2. Level of Sociality Mating strategy Communication System Kin Selection Altruism Predator Pressure Resource Defence Parental Care Foraging Patterns

3. V.C. Wynne Edwards Animal Dispersion in Relation to Social Behaviour (1962)

4. Reproductive restraint Function of communal displays Epidiectic display -allow animals to assess their own numbers

5. Reproductive restraint Epidiectic display Assessment of population size Reproductive restraint

6. Reproductive restraint - English Swift Commonly lays 2 eggs per clutch Can lay up to 5 eggs per clutch

7. Reproductive restraint - English Swift Wynne Edwards - Courtship displays allow census of local population Why the restraint? - females lay fewer eggs than they are capable

8. Reproductive restraint - English Swift Alternative explanation Why the restraint? Look at fledging success Clutch size% fledgingMean/nest 2821.64 3451.35

9. Wynne Edwards Group Selection - animals will behave in such a fashion as to sacrifice personal benefit for the benefit of the group (altruism) Difficult to explain genetically A - a gene that promotes altruism a - a gene that promotes selfishness A - can’t spread - contains automatic selection against itself

10. Wynne Edwards Difficult to explain genetically A - a gene that promotes altruism a - a gene that promotes selfishness A - can’t spread - contains automatic selection against itself p 2 + 2pq + q 2 = 1 Selection against any animal with’A’ = (1-s) P 2 (1-s) + 2pq(1-s) + q 2 = 1

11. Wynne Edwards Group Selection -reproductive restraint evolves if Benefit to group of altruism Reproductive advantage of being selfish

12. Group selection Rabbits introduced to Australia - 24 in 1859 -1950 - about 1.5 billion Control with myxoma

13. Group selection Rabbits and Myxoma Facts/Assumptions 1. ‘Group’ = all the viruses in one rabbit 2. ‘virulence’ = lethality = r [reproductive rate] 3. Over time - virus has become less virulent 4. Transmission is by mosquitoes - so p [infection] is proportional to the lifespan of the rabbit

14. Group selection Rabbits and Myxoma Virulent formHigh reproduction (selfish) Lower probability of transmission Less virulent form Low reproduction (altruistic) Higher probability of transmission

15. Group selection Rabbits and Myxoma Group selection argument -less virulent = restrained reproduction = individual sacrifice for group survival -more virulent = higher indvidual success = group extinction Individual selection argument - high ‘r’ x low transmission < lower ‘r’ x high transmission

16. Social Behaviour Costs and Benefits Benefits 1. Protection from physical factors - Aggregations

17. Social Behaviour Costs and Benefits Benefits 2. Protection against predators a. Encounter Effect Grouped animals are more difficult to find

18. Social Behaviour Costs and Benefits Benefits 2. Protection against predators a. Encounter Effect predicted observed Encounter rate Colony size

19. Social Behaviour Costs and Benefits Benefits 2. Protection against predators b. Dilution Effect 1:91:1000’s

20. How do groups form? Hamilton - Geometry for the selfish herd Circular pond Colony of frogs Water snake Colony of frogs

21. How do groups form? Hamilton - Geometry for the selfish herd At same time each day, snake appears and frogs go to side of pond Colony of frogs

22. How do groups form? Hamilton - Geometry for the selfish herd Frogs are given the opportunity to move. How??? Colony of frogs Domain of danger

23. How do groups form? Hamilton - Geometry for the selfish herd Frogs are given the opportunity to move. How??? Colony of frogs Domain of danger

24. Social Behaviour Costs and Benefits Benefits 3. Mate searching

25. Social Behaviour Costs and Benefits Benefits 4. Foraging success

26. Social Behaviour Costs and Benefits Benefits 5. Resource defense

27. Social Behaviour Costs and Benefits Benefits 6. Division of Labour Termite Castes Queen Worker King Alate Soldier

28. Social Behaviour Costs and Benefits Benefits 7. Aiding relatives

29. Social Behaviour Costs and Benefits Benefits 8. Modifying the environment

30. Social Behaviour Costs and Benefits Costs 1. Increased competition Number of aggressive acs Colony size

31. Social Behaviour Costs and Benefits Costs 2. Increased disease and parasite rates Lice/ nestling Colony size

32. Social Behaviour Costs and Benefits Costs 3. Interference with reproduction

33. Social Behaviour -Why behave altruistically? W.D. Hamilton - Kin Selection Fitness has two components Direct - gained through personal reproduction Indirect - gained through reproduction of related individuals INCLUSIVE FITNESS

34. Social Behaviour -Why behave altrustically? Need to know the coefficient of relatedness r = the probability that two individuals possess the same allele due to common ancestry Parent/offspring0.5 Full siblings0.5 Half siblings0.25 Cousins0.125 [Aunt/Uncle]/[Niece/Nephew]0.25 Grandparent/grandchild0.25

35. Social Behaviour -Why behave altrustically? Hamilton’s rule Altruism will spread if B/C > 1/r B = benefit to recipient of altruist’s help C = cost to altruist r = coefficient of relatedness

36. Social Behaviour -Why behave altrustically? Examples?? Florida Scrub Jay

37. Social Behaviour -Why behave altrustically?

38. Typical Group Breeding Pair Helpers

39. Social Behaviour -Why behave altrustically? Reproductive success - benefits to breeding pair 1.62 young /nest 2.20 young /nest Helpers (any number)

40. Social Behaviour -Why behave altrustically? Reproductive success - benefits to helper 1.94 young /nest One Helper Helper success = 1.94 - 1.62 = 0.32 x.5 (for relatedness) = 0.16

41. Social Behaviour -Why behave altrustically? Helper success = 1.94 - 1.62 = 0.32 x.5 (for relatedness) = 0.16 From previous slide: Novice breeder success = 1.02 / nest x 0.5 = 0.51

42. Social Behaviour -Why behave altrustically? Helper success = 0.16 From previous slide: Novice breeder success = 0.51 Why sacrifice 2/3 of your own success by being a helper? Other costs in being a novice breeder 1. Survivorship 2. Being forced to marginal territories 3. Greater chance of taking over home territory