Biological Exuberance: Animal Homosexuality and Natural Diversity

Sources: a complete list of references for each animal, with an indication of which ones discuss or mention homosexuality/transgender.

The appendix summarizes the occurrence of homosexuality (and in some cases, transgender) in other major animal groupings: reptiles/amphibians, fish, insects, spiders/other invertebrates, and domesticated animals. Included are tables and a complete list of references.

Mammals

Primates

Apes

Langurs and Leaf Monkeys

Macaques

Other Primates

Marine Mammals

Dolphins and Whales

Seals and Manatees

Hoofed Mammals

Deer

Giraffes, Antelopes, and Gazelles

Wild Sheep, Goats, and Buffalo

Other Hoofed Mammals

Other Mammals

Carnivores

Marsupials

Rodents, Insectivores, and Bats

Primates

APES

IDENTIFICATION: Similar to the Common Chimpanzee, but more slender and with longer limbs, a uniformly dark face, and a slight “part” in the hair on top of the head. DISTRIBUTION: Central and western Congo (Zaire); endangered. HABITAT: Tropical lowland rain forest. STUDY AREAS: Wamba and the Lomako Forest, Congo (Zaire); Yerkes Regional Primate Research Center (Georgia); San Diego Zoo; Wild Animal Park (San Diego); Frankfurt and Stuttgart Zoos, Germany.

Social Organization

Bonobos live in communities composed of large mixed-sex and mixed-age groups containing up to 60 or more individuals. These often divide into smaller, temporary subgroups that have a more fluid membership. On reaching adolescence (and becoming sexually mature), female Bonobos typically leave their home group and emigrate to a new one, while males usually remain in their home group for life. Females often form strongly bonded subgroups and are generally dominant to males. The mating system is promiscuous: males and females mate with multiple partners, and males do not generally participate extensively in raising their offspring.

Description

Behavioral Expression: Bonobos have one of the most varied and extensive repertoires of homosexual practices found in any animal. Females engage in an extraordinary form of mutual genital stimulation that, in many aspects, is unique to this species. Sometimes known as GG-RUBBING (for genito-genital rubbing), this behavior is usually performed in a face-to-face embracing position (heterosexual copulation is also sometimes done in this position, but not as often as in lesbian interactions). One female stands on all fours and literally “carries” or lifts her partner off the ground; the female on the bottom wraps her legs around the other’s waist and clings to her as they rapidly rub their genitals against one another, directly stimulating each other’s clitoris. Some scientists believe that the particular shape and location of the Bonobo’s genitals have evolved specifically for lesbian rather than heterosexual interactions. During GG-rubbing, each female rhythmically swings her pelvis from side to side—precisely timed so that each partner is thrusting in opposite directions—at a rate of about two thrusts per second. This is comparable to the thrusting rate seen in males during heterosexual interactions, but males thrust vertically rather than sideways. In addition, although both homosexual and heterosexual copulations are quite brief, same-sex interactions generally last slightly longer—an average of about 15 seconds (maximum of 1 minute) compared to about 12 seconds (maximum of 45 seconds) for heterosexual matings. Sometimes females GG-rub with the same partner several times in a row.

Two female Bonobos in Congo (Zaire) “GG (genito-genital) rubbing”

As shown by their facial expressions, vocalizations, and genital engorgement, females experience intense pleasure—and probably orgasm—during homosexual interactions. Partners gaze intensely into each other’s eyes and maintain eye contact throughout the interaction. Sometimes, females grimace or “grin” by baring their teeth wide and also utter screams or squeals that are thought to be associated with sexual climax. The Bonobo’s clitoris is prominent and well-developed; during sexual arousal it undergoes a full erection of both the shaft and glans (in humans, only the glans of the clitoris becomes enlarged), swelling to nearly twice its regular size. Remarkably, clitoral penetration has occasionally been observed between females during homosexual interactions (in captivity). When penetration occurs, the females often switch to vertical thrusting (as in heterosexual mating) rather than the usual sideways hip movements.

Two male Bonobos “rump rubbing”

A male Bonobo mounting another male from behind

Genital stimulation between females is sometimes performed in different positions: the two partners may both hang from a branch facing each other; one female may mount the other from behind; one female might lie on her back while the other stands facing away from her, rubbing her genitals on her recumbent partner’s vulva; or both females may lie on their backs or stand rump-to-rump while GG-rubbing. In the face-to-face position, females may alternate between who is on bottom and who is on top; prior to interacting, they often “negotiate” positions by lying down with legs spread to see whether the other partner wants to be on top. GG-rubbing occurs among