Intergroup conflict and the development of cooperation in juvenile vervet monkeys

Abstract

Little is known of the mechanisms that maintain risky cooperative behaviours in the absence of linguistically acquired cultural and social norms. This is especially the case when considering non-adult individuals who are theoretically assumed to be risk-averse, yet still incur the risks associated with cooperation. Using observational data from three troops of habituated wild vervet monkeys (Chlorocebus pygerythrus) and multilevel Bayesian models, I tested three explanations of how non-adult individuals in a non- linguistic species come to cooperate by participating in intergroup conflict. I first explored how individual attributes, social network position, and situational factors influence the likelihood and intensity of participation. I also tested how participation in intergroup conflict predicts whether non-adults will be groomed and if they will be groomed by their mothers. Thirdly, I investigated how similarities in intragroup social network and intergroup conflict participation network structures vary between the sexes across time. Overall, I found that non-adult participation in intergroup conflict is regulated by a myriad of individual, social, and situational factors.