Erwin, J. 1977. Factors influencing aggressive behavior and risk of trauma in the pigtail macaque (Macaca nemestrina). Laboratory Animal Science 27, 541-547.

Discussion of risk factors associated with group-housing. Provision of cover .... reduced aggression among members of stable groups. Subjects in newly-formed groups composed of unfamiliar animals sustained fewer injuries than did those in groups formed by merger of groups or subgroups of familiar animals.