Male-male sexual behaviour in adult captive stump-tailed macaque, Macaca arctoides


The present study represents the unique features of male homosexuality in forms and context, and determines whether this behaviour is sexually motivated or sociosexual in function in captive stump-tailed monkeys, Macaca arctoides. Ten incidents of homosexual encounters between α- and β-male were observed. No reciprocal mounting was observed. Every episode of homosexual encounters was initiated immediately after the heterosexual encounter between the β-male and receptive females. The main copulatory event was anal intromission followed by ejaculation outside the mountee’s body and eating of semen by both the actors. The average number of pelvic thrust was 20. Duration of pelvic thrust and copulation were 12.3 and 54.7 sec, respectively. The α-male never copulated with any of the estrous female and there was no homosexual encounter observed between α-male and γ-male, except for brief mounts. Three lines of evidences indicated that the homosexual encounters between α- and β-male were sexual behaviour, not sociosexual ones. Firstly, mountings were observed only during the mating season. Secondly, these unique mountings did not serve any sociosexual roles and did not mimic generalized pattern of social affiliation. Finally the form of homosexual encounters was same as that of heterosexual encounters. More females in the population and occurrence of male-male homosexual encounter only during the mating season did not support the concept of intraspecific sexual differences in homosexuality.

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