The evolution of social behavior: Why do social species exist? Disadvantages of living in social groups: Increased competition for food/resources Increased attraction of predators Increased parasite loads Increased rate of disease Increased rate of EPC Social subordination Reproductive interference Fieldfare. Turdus pilaris. Increased competition for food/resources Neolamprologus pulcher Social subordination

The advantage of social living Territory defense/maintenance Predator defense Offspring care Mating effort Mutualism Nesting relationships Dully colored males are likely allowed to nest near dominant males because Lowered risk of cuckoldry to dominant male.75 Easier for dominant to perform EPC Dull males gain opportunity to hold higher quality territory in exchange for increased cuckoldry 1.5

Shared mating effort Mutualism: cooperative behavior with payoff Long-tailed manikins Males work in pairs to attract females Dominant male receives all mating benefits Subordinate becomes dominant when the other male dies/disappears

Reciprocal altruism: One organism provides a benefit to another in the expectation of future reciprocation Assumes that cheaters can be identified/punished Assumes that the giver incurs a short-term personal cost Assumes that receivers are not preferentially related to givers Meerkats: Reciprocal altruists? If true: meerkats should: Share sentinel duties equally Sentinels should be at greater risk

Prisoners dilemma: Why reciprocal altruism is very rare in nature In survival terms, catching a cheater is low…when your dead! Conditions under which altruistic behavior should could occur: When there is opportunity for repeated opportunities to give/receive by the same unrelated players: tit for tat When players are related

Direct selection: altruistic acts that directly influences your personal fitness Indirect selection: altruistic acts that directly influences fitness of close relatives Kin selection: altruistic acts directed at both offspring and closely related individuals Belding’s Ground squirrels: Alarm callers are far more likely to be captured than alarm call receivers Females are twice as likely to give alarm calls How altruistic traits could spread in a population Belding’s Ground squirrels