Understanding escalated aggression over food resources in white-faced capuchin monkeys

Escalated aggression has been studied both theoretically and empirically in many species of organisms. Most studies have focused on individuals competing for mates, territories or rank within a social hierarchy. In nonhuman primates, dyadic aggression has been studied in the context of feeding trees, whereas coalitions have been studied primarily in the context of mate or rank acquisition. Although coalitions can represent a substantial fraction of agonistic interactions at feeding trees, most studies have not taken into account the effect of present ecological conditions on the occurrence of coalition formation. We examined whether there is an ecological basis to escalated aggression, defined as overt dyadic aggression and polyadic coalition formation, in wild white-faced capuchin monkeys, Cebus capucinus. Our results indicate that ecological characteristics of the feeding trees, the availability of potential allies and rank differences between interactants are important in predicting escalated aggression in this species. This is the first field study to link ecology to escalations in the form of dyadic and polyadic aggression in nonhuman primates. (C) 2007 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.