Aggressive intrasexual competition in male japanese macaques (Macaca Fuscata)

The disruption of rivals' mating activity is a prominent strategy for intrasexual competition in many mammal species. In the present study, we analyzed male aggressive harassment of consortships in a stable social group of Japanese macaques {Macaca fuscata). The group was formed by 82 monkeys including 24 adult males and 32 adult females. The group was observed for a total of 238 hrs during the 1989-1990 mating season. A total of 57 episodes of aggressive harassment by males were recorded. The intensity of harassment displayed by the aggressors ranged from stare threat to physical attack. Higher-ranking males were responsible for significantly more episodes of aggressive harassment than lowerranking males. Even after excluding the dominant male, who was responsible of 37% of all the episodes, the comparison between the males of different rank yielded a significant difference. In most cases (68%), the target of aggressive harassment was the female partner of the consort pair. The consort pairs with lower-ranking males did not receive more aggressions than those with higherranking males. Similarly, the rank of the female partner did not influence the frequency of male aggressive harassment addressed to the consort pair. In order to have an indirect evaluation of the efficacy of aggressive harassment in terms of intrasexual competition, we correlated the frequency of aggressive harassment with various measures of male sexual success. The number of episodes of aggression toward consortships made by a male did not correlate with the number of his female mating partners, the number of different females with whom the male was observed to ejaculate, and the total number of ejaculations. These results, which are in keeping with previous reports of male intrasexual competition in Old World monkeys, make it difficult to interpret the functional significance of aggressive intrasexual competition.