| Abstract: | Resistance to immigration, at least into groups larger than optimum, is an expected manifestation of competition among females in mammals with female transfer and has been reported for several such species. Contrary to this expectation, it had not been seen in mountain gorillas. The transfer of a large number of females into an already large group in 1984–85, however, provoked frequent harassment of the immigrants by resident females. The rate of harassment gradually declined, but was still high compared to smaller groups after three years. The male responsible for most mating activity often intervened to stop harassment between females, and immigrants seemed to use him as a shield against harassment. All immigrants stayed with the group, but three residents eventually emigrated. Several factors probably contributed to the difference from earlier observations: the large number of females, the high degree of relatedness among residents and, perhaps most importantly, constraints on male ability to control female conflict. Several aspects of competition may underly harassment, but its significance for reproduction is unclear. |
