Influence of sexual competition and social context on homosexual behavior in adolescent female Japanese macaques

We explored the role that sexual and social partners play in the expression of female homosexual behavior among adolescent female Japanese macaques at Arashiyama, Japan. Our data fully or partially supported all the predictions related to four non‐mutually exclusive hypotheses, namely the “adult male disinterest in adolescent females” hypothesis, the “numerous homosexual adult females” hypothesis, the “safer homosexual interactions” hypothesis and the “same‐sex sexual interactions” hypothesis. Our results show that both sexual context (e.g., lack of adolescent female attractivity toward adult males, presence of motivated same‐sex sexual partners), and social context (e.g., risk of aggression) help explain the high frequency and prevalence of homosexual behavior in adolescent females in the Arashiyama group of Japanese macaques. As with adult females, whose homosexual consortships do not reflect generalized patterns of social affiliation or kinship, we found that adolescent females’ same‐sex sexual partners were neither kin, nor were they non‐kin individuals with whom adolescent females were closely affiliated outside of a consortship context. Our study furthers the growing database of female homosexual behavior in Japanese macaques and provides additional evidence that homosexual behavior as expressed by adolescent female Japanese macaques is, like heterosexual behavior, sexual in nature. We discuss the relevance of our findings to a broader comparative approach that may shed light upon the development and evolution of human homosexuality. Am. J. Primatol. 77:502–515, 2015. © 2015 Wiley Periodicals, Inc.