Aureli, F., Veenema, H., van Eck, C. 1993. Coping with short-term crowding in long-tailed macaques. American Journal of Primatology. 31, 295 (Abstract).

Data from 42 individuals belonging to different age-sex classes showed that only mild forms of aggression increased under the crowded condition. Crowding also resulted in a decrease in grooming, playing and exploration of the environment, while it produced an increase in huddling. ... The results suggests that this group seemed to reduce the risk of severe aggression under short-term crowding simply by decreasing the level of activity.