Socio-sexual behavior in Pan paniscus and Pan troglodytes: A comparative study

Abstract

Comparative observations in a captive setting of the sexual behavior of wild born and reared Pan troglodytes and Pan paniscus revealed important and unexpected behavioral differences between these two closely related species. The external genitalia of the female Pan paniscus is rotated anteriorly, copulation takes place throughout the cycle in Pan paniscus , and homosexual copulation is a common occurrence. Vocal and gestural exchanges often precede and accompany copulation in Pan paniscus but not in Pan troglodytes . Feeding and food sharing elicit copulatory activity on virtually every occasion in Pan paniscus , but not in Pan troglodytes . Copulatory positioning among Pan paniscus is marked by considerable variability, including en face ventro-ventral positioning. These observations suggest that, at least in aspects of sexual behavior, the pygmy chimpanzee displays greater malleability and greater dependencyupon complex non-verbal signaling. In Pan paniscus , copulatory behavior is more closely intertwined with other forms of social interaction such as food sharing. The sexual behavior patterns of the pygmy chimpanzee, while still quite distinct from those of man, nevertheless display a greater degree of similarity to the sexual patterns of our own species than do those of any other living non-human primate.