Cooperation and conflict in the social lives of bats

To be evolutionarily stable, cooperative behavior must increase the actor's lifetime direct fitness (mutualism) or indirect fitness (altruism), even in the presence of exploitative, noncooperative cheaters. Cooperators can control the spread of cheaters by targeting aid to certain categories of individual, such as genetic relatives or long-term social partners. Without such discrimination, cheaters could gain the reproductive benefits of cooperation without paying the same costs and eventually outbreed cooperative phenotypes. Here, we review evidence for cooperative behaviors in bats and the possible mechanisms that might prevent cheating. Cooperative behavior in bats is shaped by ecology, life history, and social structure. Altruism without kin discrimination is unlikely to evolve through population viscosity in bats because dispersal leads to low-average relatedness in the colony or social group. On the other hand, mutually beneficial cooperation, often between unrelated individuals, is found in several bat species. Examples include social thermoregulation, male cooperation for defense of female groups, female cooperation for defense of food and pups, social grooming, and food sharing. Many forms of cooperation in bats likely involve both direct and indirect fitness benefits. Some group-living tropical bat species provide intriguing examples of costly helping behavior between unrelated individuals, but the exact mechanisms that prevent cheating remain to be elucidated.