Sex and species differences in captivereared juvenile chimpanzees and orang-utans

Abstract

The behavior of nursery-reared juvenile chimpanzees and orang-utans was studied during intraspecific group interactions in large outdoor compounds. Chimpanzees spent more time on the ground, more time in proximity to another and exhibited more slap-hit behavior than the orang-utans. Both groups exhibited only species-typical vocalizations. Males of both species were more assertive in social interactions, whereas females interacted more with inanimate objects. Positive correlations between body weight and the frequency of some social interactions partially confounded interpretation of the sex differences. The results indicate that early experience with adults is not necessary for the development of certain sexually dimorphic and species-typical behavior patterns in juvenile apes. However, early experience with peers seems to facilitate development of these patterns. The results are discussed in relation to available data on the early hormonal and social determinants of behavior in the higher Primates. © 1974.