The Effects of Kinship, Similarity, and Gender on Level of Affinitive Interaction between Captive Chimpanzees

Abstract

Kin selection does not entirely account for the choice of affiliative interactions among chimpanzees (Pan troglodytes). Other factors such as familiarity and similarity have been implicated as influences on association preferences. This study investigates the influence of kinship, similarity and gender on bond strength in a captive community of chimpanzees. The aim of the study is to determine the factors affecting social bond strength, and how these relate to the theory of kin selection that has dominated the study of primate sociality. Social bonds strength was determined between dyads using a composite of several affiliative behaviours, taking into account individual gregariousness of dyad members. Maternal kinship was not found to influence level of affiliative behaviour, supporting previous findings. Two measures of similarity (age and personality) were also found to be ineffective predictors of affiliative bonds. Male-male bonds were not found to be stronger than male-female or female-female bonds. Finally, there was no difference in gregariousness or average bond strength between males or females. The sex differences in gregariousness that are generally found in other communities are not present in this group. The lack of difference in bond strength supports evidence from some study sites emphasising female sociality. Overall, the results demand a more detailed study into the mechanism underlying association choices in chimpanzees.