Partner preferences in different aged female rhesus macaques (Macaca mulatta)

It has been suggested that there is a strong age-peer preference for social partners among aged human and nonhuman primates. The purpose of this investigation was to study the social pairings that occurred in a large (70 animal) social group of rhesus macaques. Six females in each of three age classifications (old, prime, and young adults) were observed during a breeding season and nonbreeding season to determine with whom these individuals interacted in socially affiliative ways. The study group was housed in a 38 X 38 m outdoor area and only naturally occurring interactions were observed. The results suggest strong cross-age partner preferences that affect the distribution of socially affiliative responses within the group. There was a strong preference for kin in all classes except prime aged sisters. Among nonkin only the infants were consistently preferred as target animals for socially affiliative responses.