Primate Socioecology

Abstract

Sociality is the primary behavioral adaptation of the anthropoid primates, the monkeys and apes. All of the anthropoid primates, except orangutans, spend most of their lives in stable groups of familiar individuals. Ecological factors influence the evolution of sociality, as group living is thought to enhance access to food resources and/or reduces vulnerability to predation. Ecological factors, such as the abundance and distribution of food resources, also shape behavioral strategies of group members, particularly females whose fitness depends largely on their nutritional status. For example, many species of Old World primates feed on fruit and other clumped resources. It is believed that competition over these resources favors the formation of coalitionary alliances among females, and this in turn favors female philopatry and the formation of corporate matrilineal dominance hierarchies. However, while the distribution of food explains many aspects of social organization, other factors may also influence the size and composition of primate groups. Thus, the number of males in primate groups is a joint function of the number of females in the group and the risk of predation. Moreover, many of the Old World monkey species have very similar social organizations although they now live in very different habitats, suggesting that social organization may be highly conservative. Finally, social organization may be shaped by strictly social factors, including the risk of infanticide. Thus, primate social organization may reflect the combined effects of ecological constraints, social pressures, and phylogenetic history.