Title: The ecology of male-female social relationships among East African chimpanzees
Description: As one of the most social orders of mammals, primates have been extensively studied with regard to their social relationships. These studies have mostly focused on understanding relationships formed between same-sex dyads and research on those formed between the sexes has been generally lacking. This study characterizes the nature of male-female relationships among East African chimpanzees and examines factors which effect the formation of these bonds. Using long-term data from the Kanyawara chimpanzee community, I calculated a composite association index for all adult dyads from 1995-2006. I first compared male-female dyads to same-sex dyads with respect to association strength and stability and found that male-female association was of intermediate strength between strong male-male association and weak female-female association and of reduced stability compared to both. I used the association data to also determine if particular male-female dyads form friendships characterized by differentially strong association and found that they were rare. All association patterns were strongly influenced by ranging behavior and short-term changes in reproductive state. Since frequent association is a necessary component for the formation of strong affiliative relationships in primates, I concluded that the formation of male-female relationships was rare among these chimpanzees.

This dissertation also reports the results of a year-long field study on intersexual feeding competition among the chimpanzees of the Budongo Forest. I examined whether male aggression was more common in feeding contexts, how the proximity of males affected female decisions to feed and whether males or females fed at higher quality sites when co-feeding in fruit trees. The results all indicate that feeding competition was not common between the sexes and therefore, it was not a constraint on the formation of male-female relationships at Budongo. In sum, this research suggests that male-female relationships are relatively unimportant for East African chimpanzees. This study has broader impacts on studies of primates in terms of how to better incorporate factors such as dispersal patterns, dominance and food quality into models of primate sociality. It is also significant with respect to the study of the human pair-bond and suggests that this trait originated after the split from chimpanzees.
Subjects: Chimpanzees, Behavior, Man-woman relationships, Social evolution