Early social deprivation negatively affects social skill acquisition in chimpanzees (Pan troglodytes)

In a highly social species like chimpanzees, the process by which individuals become attuned to their social environment may be of vital importance to their chances of survival. Typically, this socialization process, defined by all acquisition experiences and fine-tuning efforts of social interaction patterns during ontogeny, occurs in large part through parental investment. In this study, we investigated whether maternal presence enhances the socialization process in chimpanzees by comparing the social interactions of orphaned and mother-reared individuals at the Chimfunshi Wildlife Orphanage Trust in Zambia. As response variables, we selected social interactions during which an elaborate level of fine-tuning is assumed to be necessary for sustaining the interaction and preventing escalation: social play. Comparing orphaned (n = 8) to sex- and age-matched mother-reared juvenile chimpanzees (n = 9), we hypothesized that the orphaned juveniles would play less frequently than the mother-reared and would be less equipped for fine-tuning social play (which we assayed by rates of aggression) because of the lack of a safe and facilitating social environment provided by the mother. First, contrary to our hypothesis, results showed that the orphaned juveniles engaged in social play more frequently than the mother-reared juveniles, although for significantly shorter amounts of time. Second, in support of our hypothesis, results showed that social play of the orphaned juveniles more often resulted in aggression than social play of the mother-reared juveniles. In conjunction, these results may indicate that, just like in humans, chimpanzee mothers provide their offspring with adequate social skills that might be of pivotal importance for future challenges like successful group-living and securing competitive fitness advantages.