16 - Socioecology of Asian Colobines

Summary

For folivores, socio-ecological models predict scramble competition and egalitarian dominance relationships with female dispersal, but female Asian colobines do not all nicely fit these predictions. Alternative explanations concern an absence of competition, and the Folivore Paradox, where group size is limited by social factors such as infanticide. Relevant data are scarce, but our review shows that colobine foraging costs increase with group size, yet female fitness may increase or decrease. Dominance relationships vary from despotic to egalitarian, and are individualistic. The lack of female nepotism in despotic species (or populations) still requires explanation. Female dispersal is found in egalitarian and some despotic species, yet costs may be low if females migrate into a group with familiar females. Asian colobine social organization seems to follow one of two patterns. First, in seasonal species, food limits group size, while infanticide does not; these groups may experience contest competition. Second, in a-seasonal species groups are uni-male, the infanticide risk is high and infanticide, not food, may limit group size. This proposal requires further testing and may also apply to uni-male frugivores. This overview of the socio-ecological patterns in Asian colobines highlights that ecological and social selection pressures in interaction determine primate social organization.