Male-female relationships - from friendship to coercion

Project leader

Julia Kunz (PhD student, AIM University of Zürich)

Project staff

Sofia Vilela (Volunteer)


Orangutans are a ‘semi-solitary’ species, with a fission-fusion based social organization. The degree of sociability is tightly linked to their ecology. Yet, their social system is still not fully understood and there is evidence for differences between the two species, Pongo abelii and Pongo pygmaeus. This study aims at investigating and comparing male-female social interactions and association patterns of the two orangutan species. Males may benefit from associations by obtaining such rare mating opportunities, either directly or through building up a social relationship for future matings. However, being in prolonged association with a male and thus competing over the same food, may be costly to a female. To reduce the energetic costs of associatios, females may have counterstrategies. However, males and females’ interests also seem to collide when it comes to copulations. Forced copulations are relatively frequently reported in orangutans, yet the reason for the female’s fierce resistance is not yet resolved. In order to understand the correlates of forced copulations, we will evaluate male and female mating strategies and when these might conflict.