SOCIAL RELATIONSHIPS OF IMMIGRANT AND RESIDENT FEMALE MOUNTAIN GORILLAS .1. MALE-FEMALE RELATIONSHIPS

Adult males are important social partners for all females in mountain gorilla social groups, but male-female relationships can vary in association with variation in female residence status, male age and mating status, and relatedness. Such variation occurred in a large group observed over a 3-year period. All females associated and interacted affiliatively relatively often with a young silverback with whom all mated. Long-term resident females also did so with an old, non-breeding male to whom most were related, but recent immigrants spent little time near him and had few non-aggressive interactions with him. The old male made agonistic interventions to support relatives; interventions in female conflicts by the younger male tended to ameliorate competitive differentials that immigrants faced and may have helped him to retain them as mates. Males aggression toward females was common, most probably served as a mating tactic, and did not involve resource competition. Extensive grooming by an adolescent male suggests that males may also use affiliative behavior to develop mating relationships. Females may have competed for proximity with and social access to the younger silverback; competitive success could influence how well females and their offspring are protected by silver-backs, but the extent of such competition was not clear. Large group size may have heightened differentiation of male-female relationships and competition among females, but comparative data from smaller groups generally corroborate the findings from the large group.