Intragroup and intergroup social interactions in white-handed gibbons

One of the least studied aspects of the Hylobatidae is their social behavior. In the past, researchers have attributed this to a general lack of affiliative social interactions due to small group size and the hostile nature of intergroup encounters. Data collected on white-handed gibbons ( Hylobates lar) in Khao Yai National Park, Thailand, indicate that gibbons engage in higher rates of social behavior than had previously been appreciated. In addition to relatively high rates of intragroup social contact, gibbons engaged in social behavior, including play and grooming, with members of neighboring groups. These findings obligate a renewed consideration of the nature and function of territoriality in primates.