Psychosocial and hormonal aspects of hierarchy formation in groups of male squirrel monkeys



Accounts of primate social dominance hierarchies often imply that the achievement of superior status is a “goal”, akin to a valued resource or commodity, and that hierarchies emerge in multimale groups from prolonged competitive conflicts over social status. This possibility is not consistent with our observations of five newly formed triads of adult male squirrel monkeys (Saimiri sciureus). Stable linear hierarchies based on clear asymmetries in the direction of intermale agonism and genital displays were established quickly, with virtually no reciprocal fighting, and in the absence of rank-related differences in plasma cortisol or testosterone. Although affiliative social overtures were initiated more often by high-ranking and middle-ranking males, affiliative overtures were directed equally often toward all members of each group. From the outset of the study all males, regardless of rank, spent an average of 33% of their time huddling in affiliative contact with male cagemates. These results suggest that in newly formed groups of adult male squirrel monkeys, social hierarchies reflect an expedient convention that reduces conflict and facilitates the formation of small cohesive groups. © 1994 Wiley-Liss, Inc.