Biological Exuberance: Animal Homosexuality and Natural Diversity

KOB

IDENTIFICATION: A large grazing antelope with a reddish coat, white underparts, and black markings on the legs; males have lyre-shaped horns, while females are more slender. DISTRIBUTION: Western Kenya to Senegal. HABITAT: Open savanna near water. STUDY AREA: Toro Game Reserve, Uganda; subspecies K.k. thomasi, the Uganda Kob.

WATERBUCK

IDENTIFICATION: A 4-foot-tall (shoulder height) antelope with long, straggly brown or grayish hair and a white rump; males have sickle-shaped, ridged horns. DISTRIBUTION: Sub-Saharan Africa. HABITAT: Grassland, savanna, forest near water. STUDY AREA: Queen Elizabeth Park, Uganda; subspecies K.e. defassa, the Defassa Waterbuck.

LECHWE

IDENTIFICATION: Similar to Kob, but horns longer and thinner, and coat yellowish brown to black. DISTRIBUTION: Southeastern Zaire, Zambia, Botswana. HABITAT: Wetlands. STUDY AREAS: Chobe Game Reserve and Lochinvar National Park, Zambia; subspecies K.l. kafuensis, the Kafue Lechwe.

PUKU

IDENTIFICATION: Similar to Kob but with shorter horns. DISTRIBUTION: Scattered locations throughout south-central Africa. HABITAT: Moist savanna, floodplains, woodland. STUDY AREAS: Kafue National Park and Luangwa Game Reserve, Zambia.

Social Organization

Kob society is complex and is organized around two types of social systems: sex-segregated herds and LEKS. Outside of the breeding grounds, the antelopes congregate in same-sex herds: bachelor herds contain 400–600 males, while female herds usually have 30–50 adults (as well as young of both sexes), though they can contain as many as 1,000 antelopes. On the breeding grounds, the population is structured into a dozen or more small territories known as leks. These are small arenas that the males—and occasionally females—use for performing intricate courtship displays, and which they defend against the intrusion of other males. Females leave their herds to visit these leks, where they choose males to mate with and also interact sexually with other females. The other Kob antelopes also live in sex-segregated female and bachelor herds, although some Lechwe herds are cosexual. In addition, a few males—who do the most mating—are territorial, while some Waterbuck males are SATELLITES, associating with territorial males and occasionally mating with females.

Description

Behavioral Expression: Virtually all Kob females engage in some form of homosexual activity, ranging from simple sexual mounting of other females all the way up to elaborate courtship displays. These interactions usually take place when the females are in heat and may occur either in the female herds or on the leks. Homosexual courtship and sexual interactions consist of a rich array of stylized movements in a fixed sequence, which are all used in heterosexual courtship as well. Individual females vary in how many of these display behaviors they employ when courting another female—some use only one or two, while others employ the full repertoire. A female usually begins her homosexual courtship by PRANCING: she approaches another female with short, stiff-legged steps, her head held high and tail raised. This is followed by an action known as FLEHMEN or LIP-CURLING: she sniffs the vulva of the other female, who crouches and urinates while her partner places her nose in the stream of urine. While doing this, she retracts her upper lip in a curling gesture, exposing a special sexual scenting organ that allows her to sample the odor of the urine. Her courtship dance continues with a stylized gesture known as FORELEG KICKING: she raises her foreleg and gently touches the other female between her legs from behind. The other female responds with ritual MATING-CIRCLING, in which she circles tightly around the courting female, sometimes nipping or butting her hindquarters. This leads to mounting, in which the first female stands on her hind legs and climbs on top of the other from behind, as in heterosexual mating. Sometimes the mounting female gives a single vigorous pelvic thrust, similar to the thrusting that a male makes when he reaches orgasm.

Courtship and sexual activity between female Kob: “prancing” (above), “foreleg kicking” (middle), and mounting

Following homosexual mounting, female Kob may engage in “inguinal nuzzling” (left) and “pincers movement” (right)

Homosexual copulation may be followed by a further display of stylized behaviors. The courting female, for example, might make a distinctive whistling sound by forcing air loudly through her nostrils with her mouth closed (also made by males in heterosexual courtship). The two females may also engage in what is known as INGUINAL NUZZLING: the female who was mounted adopts a special posture with her hind legs spread wide, tail raised, back arched, and her neck extended in a graceful swanlike position. The other Kob licks her partner’s vulva and udder from behind and then concentrates on nuzzling and licking two special “inguinal glands” located in the same region, which secrete a pungent, waxy substance. Finally, the interaction concludes with what is known as the PINCERS MOVEMENT, in which one female gently holds the other in a “pincers” position with her head on the other Kob’s back and her leg raised underneath her belly. Occasionally, a female Kob will herd other females and even defend her display territory against courting males by attacking the males head-on—no small feat, considering that she does not have the horns that most males use for such purposes. The majority of Kob that participate in homosexual mounting also become pregnant and raise young—and in all cases, this is done in the female-only herds, with little or no participation from males beyond insemination.

Female homosexual mounting also occurs in three other closely related species of antelopes, the Waterbuck, Lechwe, and Puku. Interestingly, Waterbuck females that mount each other are not usually in heat, unlike Kob. Occasionally, a Waterbuck female will perform courtship flehmen with another female as well. Hermaphrodite or intersexual individuals also sometimes occur in Kob: one animal, for example, was chromosomally male and had testes and large horns, combined with a vagina, uterus, and enlarged clitoris.

Frequency: Homosexual mounting is common among Kob. Each female participates in same-sex mounting about twice an hour (on average) during the mating season, and over an entire mating season a female might mount other females 60 or more times (although most females probably engage in this activity a dozen or so times). However, because heterosexual mounting rates are extraordinarily high—more than seven times higher than homosexual rates—same-sex mounting accounts for only about 9 percent of all sexual activity. Homosexual courtship displays are less common than same-sex mounting in this species. In Puku and Lechwe, mounting between females is also common, but it occurs only occasionally among Waterbuck.

Orientation: Most, if not all, female Kob are bisexual, participating in both heterosexual and homosexual mounting, but individuals vary along a continuum in their orientation. For some, same-sex mounting makes up nearly 60 percent of their sexual activity, while for others it constitutes only 1–3 percent, but the average is about 11 percent. Fewer Kob females use courtship displays with other females, but there is a parallel range in variation. About 7 percent of females employ a significant portion of the full courtship repertoire when interacting with other females. In the other species of Kob antelopes, females that engage in homosexual mounting probably also participate in heterosexual activities as well.