Conflict avoidance among rhesus monkeys: coping with short-term crowding

Abstract

Abstract. Two contrasting models were examined, each of which predicts a relationship between space and aggression in primates. A 'spatial density' model predicts that as spatial densities increase aggressive responses also increase. A more recent 'coping model' suggests that, over long periods of time, animals will adapt to crowded conditions by increasing appeasement behaviour and allogrooming to reduce social tension and the incidence of aggression. This study evaluated these models within the context of a traditional short-term crowding experiment by examining changes in behaviour when a well-established group of 61 rhesus macaques, Macaca mulatta, was periodically crowded into a familiar area one-fifth the size of its normal enclosure. Data from a sample of 20 adult subjects of both sexes showed that no significant increases in intense aggression occurred. Only mild forms of aggressive behaviour increased under the crowded conditions (threat and rough behaviour) and increases in rough behaviour were highest towards infants. Submissive behaviour such as avoidance and the bared-teeth display increased during crowding, and increases in the bared-teeth display were highest between same-sexed adult partners. Analysis of the rank distance between the performer and recipient of bared-teeth displays indicated that increases were most pronounced from the lowest- to the highest-ranking animals. Crowding produced a general increase in huddling with a corresponding decrease in grooming, and these changes across conditions were mostly attributable to interactions among kin. Results provide only partial evidence for both models and indicate that neither one by itself is adequate to explain behaviour in short-term crowding situations. Under short-term crowding, this group appeared to adopt a conflict-avoidance strategy rather than a more active tension-reduction strategy.