Aspects of fight interference in free-ranging and compound-dwelling rhesus macaques (Macaca mulatta)

Patterns of fight interference (agonistic aiding) were compared among three groups of rhesus monkeys (Macaca mulatta) living in two settings: (1) two groups at Cayo Santiago (Caribbean Primate Center); and (2) one group at the Yerkes Regional Primate Research Center (YRPRC). A total of 1,227 interference episodes were recorded in 1,650 hours of observation. The only significant intergroup difference was the increased tendency of males at YRPRC to aid aggressors rather than victims. Among other findings, females aided relatives, interfered against target animals dominant to themselves, aided juveniles, and aided victims more consistently and frequently than did males. Importantly, female interference became more male-like in pattern when aid was given to nonrelatives. Neither the dominant males nor males in general displayed a unique or consistent tendency to interfere in fights in a manner which could be interpreted as controlling aggression. The males' interference patterns also did not suggest they were forming coalitions to either attain or defend status rankings. It is concluded that, overall, observations of compound-dwelling and free-ranging rhesus monkeys reveal similar relationships. Further, while female rhesus monkeys interfered in fights in a manner consistent with the control of aggression and protection of kin, the motives of male interferers remain unknown; however, their behavior is consistent with the hypothesis that they were reducing intermale tensions while, at the same time, minimizing physical risk.