Juvenile and adolescent chimpanzee behavioral development in complex groups

To date there have been few opportunities to study the behavioral development of captive juvenile chimpanzees (Pan troglodytes) in species-appropriate groups. This study documents the social development of 21 ( 13 female, eight male) captive chimpanzees who were born into complex breeding groups and remained in this natal setting until sexual maturity. Young males displayed the highest levels of sexual behavior, whereas females of all ages showed consistently lower levels than males. Older males showed the most aggression, with females again displaying consistently lower levels than males. Submission increased with age for both males and females. Males showed higher levels of affiliation than did females, but this difference was only slight at older ages. As all subjects matured they showed higher levels of grooming and lower levels of tandem walk/embrace. Social and solitary play declined over age for all subjects; males showed higher levels of social play than females at all ages. For aggression, social and solitary play, tandem walk/embrace, and grooming, the above results corroborate published findings from both studies of wild and captive chimpanzees. For sexual behavior and submission, these results most closely resemble those from studies on free-ranging chimpanzees. The behavioral similarity of the subjects of the current study to free-ranging chimpanzees may reflect the greater capacity of the rearing environment examined to promote species-typical social development in captive chimpanzees as compared with environments which have been previously examined in the literature.