Development of dominance and aggression in Macaques

Abstract

Social behaviours and 17-hyriroxycorticosteroids were measured in 48 laboratory-born juvenile rhesus in old and in new quadrads for 8 days composed of animals from the same dominance position. Stress and fighting increased as a function of higher previous dominance rank but lower current rank. When 40 macaques were tested in 4s, dominant monkeys were first to contact slightly novel objects, but a role analysis revealed better contact-order prediction than did rank-order for highly novel objects, most groups having their habitual first-contactor. When he was overtly punished or covertly trained to avoid objects, the group's response was altered. "Role" is extensively discussed. Rhesus (36) from 3 rearing conditions were paired for 20 wk either with therapists that were (a) socially SOPhisticated 9-mo-old monkeys, (b) 9-mo-old partial social ISOlates, or (c) socially naive 3-mo-old INFants. Aggression was greatest in those INF, ISO, and SOP paired with ISO and least in those paired with INF, opposite to predictions of a learning model of aggression. Three groups of 8 infant rhesus were assigned to one of 3 ranks — Dominant, Intermediate, or Subordinate. D-monkeys were more aloof and more disturbed by novelty. D-females and S-males appeared ill-adapted to their positions, showing more disturbance and aggression. Results suggest many behaviours found in high-ranking monkeys are due to the rank and not a characteristic of individuals. Eight stump tailed macaques were given all social experience in DARKness or half in the dark and half in the light (CONTROLS). When tested in darkness or later in light, the DARK groups showed almost no social aggression but more self-aggression and less play than controls, and darkness reduced aggression in CONTROLS. Support was found for the hypothesis that there is some direct mechanism for the nongenetic transmission of acquired levels of aggression from mother to offspring.