We aimed to explain the frequent and prevalent female homosexual behavior in the context of female-biased operational sex ratios (OSR) and qualified sex ratios (Q) in a free-ranging group of Japanese macaques (Macaca fuscata) living at Arashiyama-Kyoto, Japan. Our data included the average availability of sexually mature males during females’ putative fertile period (OSR), the ratio of sexually mature males to sexually mature females (Q), as well as heterosexual and female homosexual solicitations and consortships collected during 13 mating seasons from 136 females. Our results did not support the “heterosexual deprivation hypothesis,” which holds that female homosexual behavior is attributable to a shortage of male mates. Likewise, our results did not support the “lack of opposite-sex sexual competitor hypothesis,” which holds that females have more access to female mates when male sexual rivals are scarce. Of the 11 predictions tested, only one yielded statistically significant results: we found that higher ratios of availability of preferred female partners to preferred male partners were associated with female homosexual consortships rather than female heterosexual consortships. This result supported the “bisexual preference hypothesis,” which holds that female homosexual behavior is attributable to female preference for certain female mates relative to certain male mates. We conclude that when a female targets another female as a mate, it is an active choice for a female sexual partner over available male alternatives, rather than a by-default situation that occurs because males are not available as sexual partners, or because females are better able to access female sexual partners due to a scarcity of male sexual competitors.
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This period of data collection, prior to the main 2000-2012 period, was added to extend the longitudinal analysis and provide a more historical perspective on the phenomenon under study.
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This study was funded by the following agencies: Natural Sciences and Engineering Research Council of Canada (NSERC), Alberta Innovates Health Solutions (AIHS), Japan Society for the Promotion of Science (JSPS), American Institute of Bisexuality (AIB), the L.S.B. Leakey Foundation, as well as the Office of the Dean of Arts and Science and the Office of Research Services at the University of Lethbridge, Alberta, Canada. We thank John R. Sylla from the AIB. We thank Penny D’Agnone for help securing AIHS funding. We thank the Department of Indo-Pacific Languages and Literature at the University of Hawaii-Manoa for office space and support. We thank S. Asaba, S. Tamada, and J. Hashiguchi for permission to work at Arashiyama Monkey Park and fruitful discussion in the field. We thank the Enomoto family of Arashiyama for logistical support in Japan. We thank the Editor and one anonymous reviewer for fruitful comments on a previous version of the article.
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Leca, JB., Gunst, N., Huffman, M.A. et al. Effect of Female-Biased Sex Ratios on Female Homosexual Behavior in Japanese Macaques: Evidence for the “Bisexual Preference Hypothesis”. Arch Sex Behav 44, 2125–2138 (2015). https://doi.org/10.1007/s10508-015-0522-4
- Operational sex ratio
- Qualified sex ratio
- Female homosexual behavior
- Bisexual preference
- Non-human primates