Sexual partner preference in female Japanese macaques

Whether animals ever exhibit a preference for same-sex sexual partners is a subject of debate. Japanese macaques represent excellent models for examining issues related to sexual preference in animals because females, in certain populations, routinely engage in both heterosexual and homosexual behavior over the course of their life spans. Multiple lines of evidence indicate that female homosexual behavior in Japanese macaques is a sexual behavior, not a sociosexual one. Additional evidence indicates that female Japanese macaques do not engage in homosexual behavior simply because acceptable male mates are unavailable or unmotivated to copulate. Patterns of sexual partner choice by female Japanese macaques that are the focus of intersexual competition indicate that females of this species choose same-sex sexual partners even when they are simultaneously presented with a motivated, opposite-sex alternative. Thus, in some populations of Japanese macaques, females prefer certain same-sex sexual partners relative to certain male mates, and vice versa. Taken together, this evidence suggests that female Japanese macaques are best characterized as bisexual in orientation, not preferentially homosexual or preferentially heterosexual.