Determinants of dominance hierarchy in a captive group of pigtailed monkeys (Macaca nemestrina)

Eighteen pigtailed monkeys, all strangers to each other, were placed together in a laboratory compound. Two infants were eliminated from the study shortly after group formation. To determine dominance hierarchy aggressive-submissive interactions were observed among the remaining 16 monkeys during 4 periods covering 5 months of group development.Results suggested that 3 factors were basic determinants of dominance hierarchy: body weight for males, estrus for females, and maturity for both sexes.Aggressive-submissive interactions were far more frequent during Period I, the first hour of group formation, but decreased with stabilization of hierarchical order in subsequent periods.Aggressive-submissive interactions were not evenly distributed among all possible pairs in the group, but tended to involve mostly the high-ranking animals. Also, high-ranking animals concentrated their aggression towards more submissive monkeys of their own rank. Because low ranking animals were involved in fewer aggressive-submissive interactions, their rank determination was difficult.This research was supported by grant No. FR-00166 from the National Institutes of Health, U. S. A.