Department of Anthropology, Univeristy of Michigan
April 14, 2016 49, Atrium Ballroom A/B
Primates form strong social bonds with conspecifics in many species across the Order. These “friendships” are particularly important for adult male chimpanzees, whose bonds with other males influence the acquisition and maintenance of dominance rank and ultimately have significant fitness effects. Despite this, it is unclear when strong social bonds arise. Are friendships forged in adolescence when males begin to interact independently with group mates for the first time? If so, are bonds formed preferentially with maternal kin and age-mates, as is the case in adult males? To answer these questions, I studied 18 male chimpanzees ranging from 12 to 20 years of age at Ngogo, Kibale National Park, Uganda. During hour-long observation sessions of individual males, I recorded social behavior continuously and all males in proximity (within 5 m) of the focal male every 10 minutes. I computed the frequency that each subject was in proximity of another adolescent or adult male. Dyads that spent a disproportionate time in proximity were considered strongly bonded. All but three males, including six of the eight adolescents, formed at least one strong social bond. There was no relationship between age and the number of strong bonds individuals maintained. Three adolescents formed bonds with adults, one with a younger adolescent, and two with both adolescent age-mates and adults. Of those with maternal adolescent or adult brothers, 36% formed bonds with their kin. Although adolescent male chimpanzees are less engaged in the competitive world of adults, these results suggest that they still form friendships.
Funding provided by the Leakey Foundation, the University of Michigan, and the National Science Foundation.