RECIPROCITYAND INTERCHANGE IN THE SOCIAL RELATIONSHIPS OF WILD MALE CHIMPANZEES

Social relationships in nonhuman primates result from investments that individuals make while pursuing tness-maximizing strategies. These strategies sometimes include social exchange, either reciprocity (exchange of the same acts) or interchange (exchange of different acts). Individuals in many species may negotiate for services in biological markets, particularly grooming and agonistic support. They also may compete for access to valuable social partners. Abundant evidence for reciprocity in grooming and in support and for competition over partners exists, notably for females in some cercopithecines. However, evidence for interchange of grooming and support is scarcer, and apparent interchange may be a byproduct of correlations between grooming or support and some third variable (e.g. dominance rank). Chimpanzees have been prominent in discussions of social exchange, especially because male chimpanzees cooperate in many ways. Most analyses of interchange have used data on captive chimpanzees; these provide good evidence for reciprocity, but ambiguity with regard to interchange. Data on an unusually large chimpanzee community at 1) Author’