Immediate and delayed benefits of play behaviour: new evidences from chimpanzees (Pan troglodytes).

Evidence for the anticipation of competition at feeding time has been previously documented in both Pan species. Chimpanzees seem to cope with competitive tendency through behavioural mechanisms of tension reduction, and grooming is certainly one of these. Social play and grooming are often matched because they bring animals into close physical contact for long periods, and they have an important role in social cohesion. Our goal was to investigate the occurrence of play behaviour during the pre-feeding period, before a basic maintenance activity is about to take place, in the chimpanzee colony housed in the ZooParc de Beauval (St Aignan sur Cher, France). The group was composed of 10 adults and nine immature individuals. By scan animal sampling (344 h of observation), we recorded play and grooming interactions in all age-class combinations during four different periods (pre-feeding, feeding, post-feeding, control). We found peak levels of grooming interactions among adults during the pre-feeding time. A peak frequency at the pre-feeding time was also found in social play between adults and unrelated immature subjects. This finding suggests that during high tension periods, grooming and play might share similar functions in conflict management. Like grooming, play might have an important role to limit aggression and increase tolerance around food (immediate benefits). Immature animals showed a higher frequency of play in the pre-feeding than in any other condition (feeding, post-feeding, and control). During high excitement periods social play probably represents a safe mechanism for immature subjects to test their personal abilities (self-assessment), the strength/weakness of playmates, and the degree of cooperation/competition with them (social-assessment). In the light of this new evidence, we can assert that play behaviour is far from being a purposeless activity, at least in the chimpanzee colony under study