Most primates are social animals and live in groups. Primates that subsist on sparse resources are most likely to live in groups because they can defend resources from other populations better than could a solitary animal. Primates that are vulnerable to predators, like those that spend time on the ground, might form groups as protection from those predators.

Primates form many different types of groups. The type formed by a particular species varies based on the lifestyle of the group-semiterrestrial or arboreal, diet, how the young are cared for, and other factors. Types of groups include female-offspring units, monogamous pairs, polyandrous groups, one-male-several-female groups, multimale groups, and fission-fusion societies.

The most ideal way to study any animal is in the field where the natural behavior of that animal can be observed in its own habitat. However, it is often not practical to conduct a complete field study. In these cases, provisioned colonies become an alternative to field studies. Primates are also studied in the zoo and in the laboratory.

Case studies of the social behavior of four primate species are examined in this chapter: the gibbon, the gelada, the savanna baboon, and the chimpanzee. Each represents its own set of adaptations and adjustments to the environment in which it lives. However, certain themes of behavior emerge from these studies. For example, agonistic behavior appears to be characteristic of each of the groups. In multimale groups, male dominance hierarchies tend to form, yet most dominance behavior is expressed by gesturing rather than actual fighting. Grooming behavior occurs frequently among primates as an expression of close social ties. The protection and care of the infant by the mother and other adults of the social unit also appear to be a universal theme of primate social behavior.