Social play of juvenile and adolescent chimpanzees in the Mahale Mountains National Park,Tanzania

Social play of juvenile and adolescent chimpanzees (Pan troglodytes schweinfurthii) in the Mahale Mountains National Park, Tanzania, was studied, by analyzing processes of play and interindividual relationships in play. The results are discussed in relation to communication mechanisms. Play was initiated in several ways. Communication about play seems to depend on the receiver's interpretation: They can interpret the sender's behavior as play, referring to (1) play signals accompanied by the behavior, (2) transformation of the behavior in timing, strength, or rhythm, and (3) situation of the occurrence. Initiation attempts sometimes failed because one hesitated in playing with the other. Although the stronger often reduced his/her activity during play, play tended to escalate in activity. Players may enjoy such escalation. Play also had a mechanism not to escalate into fighting. Play was influenced by individuals other than the players. The third party's movement often affected the players' interaction. The term play does not indicate a behavior itself but the context of the behavior: The players interpret their behaviors in their play context.