• orphans
• social deprivation
• maternal loss
• chimpanzee
• play

In this project, we investigated the playful activity in four groups of chimpanzees (Pan troglodytes) living in semi-wild conditions. We found that play is modulated by intrinsic features of the players and social variables. Indeed, the frequency of solitary was higher for immature subjects compared to adult individuals, but for social play it was generally lower in more tolerant groups compared to less tolerant ones. We also found that being orphan and living in an impoverished social environment was correlated with a reduction of the motivation to play, resulting in lower frequency of dyadic social play compared to juveniles living in other groups. Moreover, the outcome of the sessions was more frequently negative if an older individual was the initiator, but this was not connected with the restricted capabilities of orphans because they showed similar Roughness Index (RI) to other juveniles and the lowest proportion of badly ended bouts. Conversely, playful bouts lasted longer when they involved mother-reared juveniles compared to sessions including orphan individuals. We found the phenomenon of facial mimicry in the studied chimpanzees, and it was tendentially lower when individuals of different sexes were involved in a playful bout compared to play sessions including same-sex individuals, but again no differences were observed between orphans and mother-reared subjects.