Skewed sex ratios and female homosexual activity in Japanese macaques: An experimental analysis

In this paper we present the results of a behavioral experiment conducted t o test whether homosexual consortships and sexual solicitations among femal e Japanese macaques (Macaca fuscata) increase in the context of operational sex ratios that are heavily skewed towards females. The study involved a b aseline period of observation on an intact social group which had a female- biased sex ratio typical of this species. During the experimental period wh ich followed, we created a sub-group with an operational sex ratio that was heavily skewed towards females. Compared to the baseline period, females s olicited significantly more same-sex individuals for sex and formed signifi cantly more homosexual consortships during the experimental period of the s tudy. Females did not appear to engage in homosexual activity during the st udy's experimental period simply because they lacked heterosexual alternati ves. Instead, we suggest that an abundance of certain types of preferred, s ame-sex sexual partners and/or a scarcity of opposite-sex sexual competitor s best account for the increased levels of female homosexual behavior obser ved at this time.