1. Living in a group Costs of group living Benefits of group living –Predation avoidance –Resource acquisition Optimal group size

2. Costs of group living Competition for resources Increased risk of parasitism or disease Increased opportunities for reproductive interference or suppression

3. Competition for food in fieldfares Nestlings die primarily from starvation

4. Ectoparasitism in cliff swallows Nests treated with insecticide produce much larger chicks

5. Reproductive interference Brood parasitism, Extra-pair copulations Reproductive suppression

6. Predation avoidance benefits Reduce encounter rate with predator –Protected sites –Selfish herd Reduce success of predator –Vigilance –Dilution –Confusion, predator-predator interference –Mobbing, cooperative defense

7. Protected sites

8. The selfish herd

9. Predator dilution

10. Vigilance

11. More eyes and ears

12. Predator confusion

13. As school size of prey increases, capture success decreases

14. Predator interference “Schreckstoff” Schreckstoff attracts other pike, which increases handling time

15. Cooperative defense: mobbing

16. Resource access benefits Passive attraction to limited resource Active attraction due to joint benefits –Reduce path overlap –Information transfer information center producers-scroungers acquire public information –Group foraging –Communal hunting

17. Passive attraction Butterflies at a salt deposit

18. Information transfer?

19. Information transfer in osprey

20. Information transfer in evening bats Leaders “produce”, followers “scrounge”

21. Two pigeons produced, 14 scrounged

22. The producer-scrounger game Spice finch were taught to open lids and were producers. Other birds had to wait to scrounge

23. Public information Forager joins group to acquire information about food availability and/or predator risk By observing foraging success of others in the group, a naïve forager can estimate the quality of a food patch Starlings left empty patches sooner when foraging with a partner than when foraging alone.

24. Public information

25. Reduce path overlap Proposed for sparrow flocks in Mojave desert. Never been tested.

26. Group foraging

27. Cooperative hunting Permits capture of prey larger than possible by singletons

28. Optimal group size

30. Group hunting in wild dogs Larger packs kill larger prey, have higher capture success, and travel shorter distances in a hunt, but must share kills with more members of the group

31. Optimal size of wild dog foraging groups

32. Lion foraging success