Sexual Reward via Vulvar, Perineal, and Anal Stimulation: A Proximate Mechanism for Female Homosexual Mounting in Japanese Macaques

Abstract

Female Japanese macaques (Macaca fuscata), in certain captive and free-ranging populations, frequently engage in same-sex mounting. Traditionally, same-sex mounting interactions in animals have been characterized as "sociosexual," that is, sexual in terms of their superficial form, but enacted to facilitate adaptive social goals. Sexual motivation is rarely ascribed to sociosexual interactions because their adaptive functions are often seen as their primary purpose, thus diminishing, or even negating, any sexual component that such activity might have. A substantial number of studies indicate that female-female mounting in Japanese macaques is not a sociosexual behavior. In contrast, several lines of circumstantial evidence suggest that these interactions are, indeed, sexual. In this study, we documented patterns of vulvar, perineal, and anal (VPA) stimulation during same-sex mounting in female Japanese macaques. During the majority of female-female mounts analyzed, female mounters engaged in repetitive VPA stimulation. Two forms of VPA manipulation by female mounters were observed. First, while sitting in a jockey-style position on the mountee, a female mounter would rub her VPA region against the mountee's back. Males never executed this type of mount posture or pelvic movement. Second, female mounters rubbed their VPA regions with their tails during same-sex mounts. Females mounters moved their tails in a voluntary, sex-specific manner and were never observed to do so in non-sexual contexts. Given the primary role of the VPA regions in mediating sexual response in primates, the results of this research provide direct evidence bearing on the sexual nature of female-female mounting in Japanese macaques and give further support for the conclusion that the term "homosexual behavior" is an appropriate label for these interactions.

Homosexual Fellatio: Erect Penis Licking between Male Bonin Flying Foxes Pteropus pselaphon

“…pselaphon are linked to (i) the social bond and (ii) social tension regulation hypotheses [8] because of the existence of cooperation in forming clusters and competition among males for mating in the roost [16]. The social bond hypothesis proposes that homosexual behavior provides psycho-physical rewards via pleasure and reinforces long-term relationships [8,23]. Thus, homosexual fellatio would convey the intention to cooperate in forming a cluster between the fellatio actor and receiver.…”

“…Homosexual behavior may be sexually dimorphic in P . pselaphon , as in Japanese macaques Macaca fuscata [23] and M . thibetana [3].…”

Male-Male Mounting Behaviour in Free-Ranging Golden Snub-Nosed Monkeys (Rhinopithecus roxellana)

“…There is no a priori reason to reject the possibility that such mounting behaviour might be reinforced by the pleasurable (hedonic) feedback that occurs during pelvic thrusting and genital stimulation. Examples of such behaviour, sometimes resulting in orgasm, have been reported for females of several Old World anthropoids (e.g., Macaca arctoides [Chevalier-Skolnikoff, 1974]; M. fuscata [Vasey and Duckworth, 2006]; Pan paniscus [Kano, 1992]). Examples of male-male interactions of this type are less well documented, but the behaviour of the adult male LD with the subadult BF may represent a case of such sexual stimulation in R. roxellana.…”

Sexual attractiveness: a comparative approach of morphological, behavioral neurophysiological signaling in women and nonhuman primate females

“…Besides otheu genital stimulations techniques, mounteus uubbed theiu VPA on theiu female pautneus ou mounteus stuoked theiu VPA with theiu own tail (Vasey & Duckwouth 2006). Because the VPA uegion mediates sexual auousal in humans and nonhuman puimates, the authous inteupuet theiu uesults as an immediate sexual uewaud.…”