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27.4 Social Behavior KEY CONCEPT Social behaviors enhance the benefits of living in a group. 27.4 Social Behavior Living in groups also has benefits and costs. • Social behaviors evolve when the benefits of group living outweigh its costs. – benefits: improved foraging, reproductive assistance, reduced chance of predation – costs: increased visibility, competition, disease contraction • Group living requires learning social structure and membership. 27.4 Social Behavior Social behaviors are interactions between members of the same or different species. • Animals use communication to keep in contact. – visual – sound – touch – chemical 27.4 Social Behavior • Courtship displays are used to evaluate the fitness of a potential mate. • Defensive behaviors are used to protect the individual and/or the group. 27.4 Social Behavior Some behaviors benefit other group members at a cost to the individual performing them. • There are many types of helpful social behavior. – cooperation – reciprocity – altruism 27.4 Social Behavior • In altruism, an individual reduces its own fitness to help other members of its social group. – inclusive fitness – kin selection 27.4 Social Behavior Eusocial behavior is an example of extreme altruism. • Eusocial species live in large groups of mostly nonreproductive individuals. – haplodiploid species: social insects (wasps, bees, ants) Queen Minor worker Major worker – diploid species: termites, snapping shrimp, naked mole rats • Eusocial behaviors likely evolve by kin selection.
