LONG-TAILED MACAQUES AVOID CONFLICTS DURING SHORT-TERM CROWDING

Crowding has been viewed as a factor eliciting increased levels of agg ression and tension in gregarious animals. The present study tested pr edictions derived from two models, the ''density/aggression'' model an d the ''active coping'' model, which have been proposed to explain the responses of primates to crowding. In particular, we investigated the responses of a well-established group of long-tailed macaques (Macaca fascicularis) to short-term crowding. The group was periodically crow ded for 2-3 hr into a familiar area. Control observations were carried out when the monkeys were in a six times larger enclosure. Data from 42 individuals belonging to different age-sex classes showed that only mild forms of aggression increased under the crowded condition. Crowd ing also resulted in a decrease in counteraggression, allogrooming, pl aying, and exploring the environment, while it produced an increase in huddling with companions. The frequency of reconciliation and redirec tion was not affected by crowding. These findings do not support eithe r of the models but suggest that macaques adopt a ''conflict-avoidance strategy'' during short-term crowding. They reduce the risk of severe aggression in an environment where interindividual distances are smal l by simply decreasing the level of activity. Interestingly, however, when aggression occurs during crowding, tension reduction mechanisms s uch as reconciliation and redirection are used as often as in control conditions, (C) 1995 Wiley-Liss, Inc.