Japanese macaques: Some adult females mount adult males in the context of heterosexual consortships; this research has implications for the evolution of non-conceptive sex in primates

Is female-male mounting functional? An analysis of the temporal patterns of sexual behaviors in Japanese macaques. Noëlle Gunst et al. Physiology & Behavior, June 3 2020, 112983. https://doi.org/10.1016/j.physbeh.2020.112983

Highlights
• Behavioral structure contributes to testing hypotheses about behavioral function
• Temporal analysis of mating sequences helps test the function of female-male mounts
• Female-male mounting may be a sexual solicitation in Japanese monkeys
• Female-male mounting may be a sexual adaptation in Japanese monkeys
• Our research has implications for the evolution of non-conceptive sex in primates

Abstract: In certain populations of Japanese macaques, adult females mount adult males in the context of heterosexual consortships (i.e., temporary but exclusive sexual associations between a male and a female). Previous research suggested that, in this primate species, female-male mounting (FMM) may be a behavioral adaptation. This functional hypothesis holds that FMM is a (special) courtship behaviour, or a (super) sexual solicitation, that serves the function of focusing the male's attention, preventing him from moving away, and expediting male-female mounting, in the context of high female competition for male mates. In this study, we aimed to test some of the proposed functional features of FMM in Japanese macaques by comparing the temporal structure of mating behavioral sequences, including various well-known sexual solicitations, exhibited during heterosexual consortships with and without FMM. To identify and compare recurring series of behavioral events within and across sequences, we used a temporal analysis known as “T-pattern detection and analysis”. Our results (partly) supported the “FMM as a (super) sexual solicitation” hypotheses, and supported the “FMM as a sexual adaptation” hypothesis. The utilization of TPA allows for the detection of hidden features of primates’ behaviors otherwise undetectable by using conventional quantitative approaches, such as the calculation of frequencies or durations of isolated behavioral components, disjointed from the comprehensive behavioral architecture. This study fits into the scheme of a broader investigation of the functionality of non-conceptive mounting patterns observed in Japanese macaques and a reconstruction of their evolutionary history.

Keywords: Structure-functionTemporal structureT-pattern analysisNon-conceptive sexAdaptationEvolutionary by-product