Biological Exuberance: Animal Homosexuality and Natural Diversity

sexes mate with multiple partners. Smaller Crested Black Macaque groups (6–15 individuals) may contain only one adult male.

Description

Behavioral Expression: Pig-tailed Macaques engage in homosexual mounting as well as kissing. Male Pigtails mount each other using the posture found in heterosexual mating (one male behind the other, hands grasping the loins, and feet clasping the calves of the other), sometimes with erection of the penis and pelvic thrusting (though anal penetration does not occur). Females use the same position and also occasionally thrust against their female partner; the mounting female is usually in heat. Some Pigtails engage in same-sex mounting with only one partner, while other Pigtails have several partners (as many as seven for females, though the average is three). Individuals differ as to whether they prefer mounting or being mounted in homosexual encounters: a few animals engage in only one or the other, while most exhibit a range of mounter/mountee behavior. Males may even mount each other reciprocally, exchanging positions in different mounting sessions. Same-sex kissing (mouth-to-mouth contact) occurs more often than heterosexual kissing and is most common between females. However, many female homosexual mounts are “forced” in the sense that the animal being mounted does not solicit the mounting, and aggression may also be involved: 48 percent of mounts between females are nonconsensual, compared to 18 percent of heterosexual ones. No mounts between males are forced. Some same-sex mounting is incestuous, e.g., between mother and daughter or siblings of either sex.

Crested Black Macaques also participate in male and female homosexual mounting, similar in many ways to that found in Pigtails. Females often reach back to clasp the leg of a female mounting them, which is believed to be a sign of orgasm (it also occurs in heterosexual mounting), while males being mounted by other males frequently fondle their own penis. Mounting is sometimes preceded by a gesture of invitation known as REAR-END FLIRTATION, in which one male walks by another and presents his hindquarters. Younger males often mount older ones in this species. A number of other homosexual activities occur in Crested Black Macaques. Females engage in a form of mutual masturbation unique to homosexual interactions, in which they stand side by side facing in opposite directions (draping an arm over the other’s waist) and fondle and sniff each other’s vulva, sometimes with direct clitoral stimulation. Males often participate in a form of erotic grooming: one male uses his hands, lips, and tongue to groom the other, who usually has an erection and may masturbate himself by rolling his penis between his palms or licking it (he usually eats his own semen if he ejaculates). The grooming animal is often sexually aroused, too, as evidenced by his erection. Males (especially younger ones) also use a number of ritualized erotic “greeting” gestures with one another, including embracing, face-licking or kissing, fondling or grabbing of the erect penis, mounting, and rump fingering.

Frequency: Same-sex mounting occurs frequently in Pig-tailed Macaques, accounting for 7—23 percent of all mounting activity. More than three-quarters of all kissing occurs between females. In Crested Black Macaques, about 5—8 percent of all mounting activity occurs between males. Ritualized penis-grabbing or fondling between males takes place regularly in this species and can be observed weekly, and perhaps even daily, in some wild populations.

Two female Crested Black Macaques masturbating each other

Orientation: Most Pig-tailed Macaques are probably bisexual, engaging in both same- and opposite-sex mounting. However, individuals vary along a continuum of what percentage of their activity is homosexual: for some males, it is as little as 8 percent, while for others, nearly two- thirds of their mounting activity is same-sex. Although less specific information is available for Crested Black Macaques, they appear to have a similar orientation profile: in one wild troop, for example, all males participated in both heterosexual and homosexual mounting (as well as penis-grabbing) to varying degrees.

Nonreproductive and Alternative Heterosexualities

As noted above, some heterosexual copulations in Pig-tailed Macaques are forced, in that the female is an unwilling participant. Furthermore, more than a third of aggressive interactions in Pigtails are between males and females (73 percent are directed by the male against the female). Infanticide has also been seen among captive Pigtails—in some cases, infants as young as one day old have died from head and neck injuries inflicted by adult males. In addition, a 33—year study of this species (spanning seven generations and nearly 400 individuals) found that one in eight infants is physically abused or neglected by its mother. This includes being dragged across the ground, having its fingers or tail chewed, suffering severe eye damage or blindness as a result of compulsive grooming around the eyes, having its head or body crushed on the ground, and/or being rejected, abandoned, or starved by its mother. Physical abuse accounts for about a third of all Pigtail infant injuries or deaths; it appears to run in families and is usually repeated with successive offspring. Infants can also be injured when they are kidnapped, which occurs only occasionally and is typically carried out by a nonbreeding female.

A number of nonreproductive sexual behaviors occur in these two species as well. In Pigtails, males mount nonovulating females 8—15 percent of the time, and 1—2 percent of heterosexual behavior involves females mounting males (REVERSE mounts). In addition, female Pigtails may mate with up to five different males during a single period of heat. Mother-son mountings occur as well. In both of these species, heterosexual mounting sometimes does not involve penetration: nearly a fifth of Crested Black male-female mounts, for example, are “ritualized” or non-copulatory. Male Pigtails and Crested Black Macaques also masturbate, occasionally eating their own semen, while female Crested Black Macaques sometimes masturbate by inserting a finger into the vagina and simultaneously slapping their rump with one hand. Infant and very young male Crested Blacks often mount adult females, performing pelvic thrusts and even achieving penetration. Finally, spontaneous abortions occur among Pigtails, often associated with a number of physiological changes in the female’s blood chemistry: one study in captivity found that 14 percent of pregnancies terminated in abortions (among females not otherwise at high risk for miscarriages).

Other Species

Homosexual mounting occurs in three other species of Macaques: Lion-tailed (Macaca silenus), Tonkean (Macaca tonkeana), and Moor (Macaca maurus) Macaques. In the latter two species, 11—13 percent of mounting activity is same-sex.

Sources

*asterisked references discuss homosexuality/transgender

*Bernstein, I. S. (1972) “Daily Activity Cycles and Weather Influences on a Pigtail Monkey Group.” Folia Primatologica 18:390-415.

*———(1970) “Primate Status Hierarchies.” In L. A. Rosenblum, ed., Primate Behavior: Developments in Field and Laboratory Research, vol.1, pp. 71—109. New York: Academic Press.

*———(1967) “A Field Study of the Pigtail Macaque (Macaca nemestrina).” Primates 8:217-28.

Bernstein, I. S., and S. C. Baker (1988) “Activity Patterns in a Captive Group of Celebes BlackApes (Macaca nigra).” Folia Primatologica 51:61-75.

*Bound, V., H. Shewman, and J. Sievert (1988) “The Successful Introduction of Five Male Lion-tailed Macaques (Macaca silenus) at Woodland Park Zoo.” In AAZPA Regional Conference Proceedings, pp. 122-31. Wheeling, W.Va.: American Association of Zoological Parks and Aquariums.

*Caldecott, J. 0. (1986) An Ecological and Behavioral Study of the Pig-Tailed Macaque. Basel: Karger.

*Dixson, A. F. (1977) “Observations of the Displays, Menstrual Cycles, and Sexual Behavior of the ‘Black Ape’ of Celebes (Macaca nigra).” Journal of Zoology, London 182:63-84.

*Giacoma, C., and P. Messeri (1992) “Attributes and Validity of Dominance Hierarchy in the Female Pigtail Macaque.” Primates 33:181-89.

*Kaufman, I. C., and L. A. Rosenblum (1966) “A Behavioral Taxonomy for Macaca nemestrina