Biological Exuberance: Animal Homosexuality and Natural Diversity

homosexual behavior is sometimes interspersed with, or develops out of, heterosexual interactions when more than one male is involved. However, much homosexual activity occurs independent of heterosexual activity, and some males may engage primarily in same-sex interactions.

Nonreproductive and Alternative Heterosexualities

Heterosexual interactions in West Indian Manatees often involve considerable harassment and coercion of females by males. Large, jostling herds containing as many as 17-22 males relentlessly pursue females in heat as well as nonfertilizable females, attempting to copulate with them and often following them for weeks at a time. In her attempts to escape from the males, the female may violently slap her tail, twisting and turning as she dives away, or else tear through the underwater vegetation, even plunging into the mud or stranding herself onshore. Calves whose mothers are being pursued sometimes get lost or are fatally fatigued or injured. Female Manatees generally reproduce only once every three years, and at any given time, only about 30-40 percent of all females are reproducing. Most male Manatees have a distinct seasonal sexual cycle as well, with their testes generally dormant and not producing sperm during the winter months. Females raise their young on their own with no help from the males. However, a mother will occasionally allow another female to nurse her calf or may leave her calf in the company of other mothers and/or their calves while she goes off to feed on her own.

Other Species

Homosexual activity has also been observed in Dugongs (Dugong dugon), a species of Manatee that inhabits Australasian waters. A pair of captive males, for example, engaged in courtship and sexual behaviors with each other, including rolling, nudging, gentle biting, and splashing, often with erect penises. Although same-sex activity has yet to be documented in wild Dugongs, most observations of mating activity for this species in the wild involve individuals whose sex has not been unequivocally determined.

Sources

*asterisked references discuss homosexuality/transgender

*Anderson, P. K. (1997) “Shark Bay Dugongs in Summer. I: Lek Mating.” Behavior 134:433–62.

*Bengtson, J. L. (1981) “Ecology of Manatees (Trichechus manatus) in the St. Johns River, Florida.” Ph.D. thesis, University of Minnesota.

*Hartman, D. S. (1979) Ecology and Behavior of the Manatee (Trichechus manatus) in Florida. American Society of Mammalogists Special Publication no. 5. Pittsburgh: American Society of Mammalogists.

*———(1971) “Behavior and Ecology of the Florida Manatee, Trichechus manatus latirostris (Harlan), at Crystal River, Citrus County.” Ph.D. thesis, Cornell University.

Hernandez, P., J. E. Reynolds, III, H. Marsh, and M. Marmontel (1995) “Age and Seasonality in Spermatogenesis of Florida Manatees.” In T. J. O’Shea, B. B. Ackerman, and H. F. Percival, eds., Population Biology of the Florida Manatee, pp. 84–97. Information and Technology Report 1. Washington, D.C.: U.S. Department of the Interior.

Husar, S. L. (1978) “Trichechus manatus.” Mammalian Species 93:1–5.

*Jones, S. (1967) “The Dugong Dugong dugon (Muller): Its Present Status in the Seas Round India with Observations on Its Behavior in Captivity.” International Zoo Yearbook 7:215–20.

Marmontel, M. (1995) “Age and Reproduction in Female Florida Manatees.” In T. J. O’Shea, B. B. Ackerman, and H. F. Percival, eds., Population Biology of the Florida Manatee, pp. 98–119. Information and Technology Report 1. Washington, D.C.: U.S. Department of the Interior.

Moore, J. C. (1956) “Observations of Manatees in Aggregations.” American Museum Novitates 1811:1–24.

*Nair, R. V., R. S. Lal Mohan, and K. Satyanarayana Rao (1975) The Dugong Dugong dugon. ICAR Bulletin of the Central Marine Fisheries Research Institute no. 26. Cochin, India: Central Marine Fisheries Research Institute.

Preen, A. (1989) “Observations of Mating Bevavior in Dugongs (Dugong dugon).” Marine Mammal Science 5:382-87.

*Rathbun, G. B., J. P. Reid, R. K. Bonde, and J. A. Powell (1995) “Reproduction in Free-ranging Florida Manatees.” In T. J. O’Shea, B. B. Ackerman, and H. F. Percival, eds., Population Biology of the Florida Manatee, pp. 135-56. Information and Technology Report 1. Washington, D.C.: U.S. Department of the Interior.

Reynolds, J. E., III. (1981) “Aspects of the Social Behavior and Herd Structure of a Semi-Isolated Colony of West Indian Manatees, Trichechus manatus.” Mammalia 45:431-51.

———(1979) “The Semisocial Manatee.” Natural History 88(2):44-53.

Reynolds, J. E., III., and D. K. Odell (1991) Manatees and Dugongs. New York: Facts on File.

*Ronald, K., L. J. Selley, and E. C. Amoroso (1978) Biological Synopsis of the Manatee. Ottawa: International Development Research Center.

Hoofed Mammals

DEER

WHITE-TAILED DEER

IDENTIFICATION: A medium-sized deer (approximately 3 feet tall at shoulder) with a white undertail and multipronged antlers that sweep forward. DISTRIBUTION: Southern Canada, United States except Southwest, Mexico south to Bolivia and northeastern Brazil. HABITAT: Varied, from thickets to open country. STUDY AREAS: Welder Wildlife Refuge, Sinton, Texas; Edwards Plateau, Llano County, Texas; subspecies 0.v. texanus, the Texas White-tailed Deer.

MULE DEER

IDENTIFICATION: A stocky, grayish deer with a black-tipped tail and antlers that branch into two equal portions. DISTRIBUTION: Western North America, northern Mexico. HABITAT: Semiarid forest, brushlands. STUDY AREAS: Waterton and Banff National Parks, Alberta, Canada; University of British Columbia, Canada; near Fort Collins, Colorado; subspecies O.h. hemionus, the Rocky Mountain Mule Deer, and O.h. columbianus, the Black-tailed Deer.

Social Organization

During most of the year, White-tailed and Mule Deer live in sex-segregated groups: females form groups with other does and their offspring, while males (bucks) live in “bachelor” groups or on their own. During the rutting season, males form short-lived, consecutive “tending bonds” with multiple females—a form of polygamy or “serial monogamy.” Larger cosexual groups may also form during the winter.

Description

Behavioral Expression: Adult male White-tailed Deer sometimes mount each other, as do yearling males (especially during the nonbreeding season); occasionally a younger male mounts an older one during this activity. Homosexual mounts (like heterosexual ones) are usually preceded by one male nuzzling the other’s rear end, and sometimes one male mounts another twice in a row; occasionally the mounting buck has an erection. The mount may be briefer than a male-female copulation, but the same duration as heterosexual nonreproductive mounts (5-15 seconds, as opposed to 15-20 seconds). Yearling Mule Deer occasionally mount each other during SPARRING MATCHES—ritualized, nonviolent contests in which the bucks lock horns. During this activity one male might assume a stiffened posture, similar to a female’s before copulation. The other male—sometimes younger or smaller than the first—then mounts him, after first licking and