List of animals displaying homosexual behavior

For these animals, there is documented evidence of homosexual behavior of one or more of the following kinds: sex, courtship, affection, pair bonding, or parenting, as noted in researcher and author Bruce Bagemihl's 1999 book Biological Exuberance: Animal Homosexuality and Natural Diversity.

Bagemihl writes that the presence of same-sex sexual behavior was not "officially" observed on a large scale until the 1990s due to observer bias caused by social attitudes towards nonheterosexual people, making the homosexual theme taboo.Bagemihl (1999)News-medical.net (2006) Bagemihl devotes three chapters, "Two Hundred Years at Looking at Homosexual Wildlife", "Explaining (Away) Animal Homosexuality" and "Not For Breeding Only" in his 1999 book Biological Exuberance to the "documentation of systematic prejudices" where he notes "the present ignorance of biology lies precisely in its single-minded attempt to find reproductive (or other) 'explanations' for homosexuality, transgender, and non-procreative and alternative heterosexualities."Bagemihl (1999) page 213

Petter Bøckman, academic adviser for the Against Nature? exhibit, stated "[M]any researchers have described homosexuality as something altogether different from sex. They must realize that animals can have sex with who they will, when they will and without consideration to a researcher's ethical principles." Homosexual behavior is found amongst social birds and mammals, particularly the sea mammals and the primates. In 1986, it was even discovered amongst insects when butterfly scientist W.J. Tennent observed four male Mazarine blues competing for the attention of another male in Morocco.

Sexual behavior takes many different forms, even within the same species and the motivations for and implications of their behaviors have yet to be fully understood. Bagemihl's research shows that homosexual behavior, not necessarily sex, has been documented in about five hundred species as of 1999, ranging from primates to gut worms.Harrold (1999) Homosexuality in animals is seen as controversial by social conservatives because it asserts the naturalness of homosexuality in humans, while others counter that it has no implications and is nonsensical to equate natural animal behaviors to morality.Solimeo (2004)Solimeo (2004b) Sexual preference and motivation is always inferred from behavior. Thus homosexual behavior has been given a number of terms over the years. The correct usage of the term homosexual is that an animal exhibits homosexual behavior, however this article conforms to the usage by modern research,Bagemihl (1999) pages 122-166Roughgarden (2004) pp.13-183Vasey (1995) pages 173-204Sommer & Vasey (2006) applying the term homosexuality to all sexual behavior (copulation, genital stimulation, mating games and sexual display behavior) between animals of the same sex.

In October 2023, biologists reported studies of mammals (over 1,500 different species) that found same-sex behavior (not necessarily related to human orientation) may help improve social stability by reducing conflict within the groups studied.

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Mammals

Selected mammals from the full list

Baboon BisonBagemihl (1999) page 405 Bonobo Brown bearBagemihl (1999) page 441 Brown RatBagemihl (1999) page 469 Cavy CaribouBagemihl (1999) pages 388,389 Cat (domestic)Bagemihl 1999) pages 81, 88 Cattle (domestic)Bagemihl (1999) pages 81, 82, 89 Chimpanzeede Waal (2001)Liggett (1997–2006)Imaginova (2007j)Bagemihl (1999) pages 276–279 Common dolphinBagemihl (1999) page 339 Common marmosetBagemihl (1999) page 334 DogBagemihl (1999) pages 310, 314 Dolphinname="Biol. Exuberance: Dolphin ElephantBagemihl (1999) page 427 FoxBagemihl (1999) pages 218, 231, 317 GiraffeBagemihl (1999) page 391Imaginova (2007d) Goat Horse (domestic)Bagemihl (1999) pages 81, 165, 205, 226, 231 HumanBagemihl (1999) page 432Wellings, K., Field, J., Johnson, A., & Wadsworth, J. (1994). Sexual behavior in Britain: The national survey of sexual attitudes and lifestyles. London, UK: Penguin Books. Humpback whale KoalaBagemihl (1999) page 455-457 Lion Sheep Orca Southern right whale Wolf

Birds

Homosexual behaviour is demonstrated by 120 known species of birds. While an uptick in research on bird homosexuality – and animal homosexuality in general – has been coming out in recent years, it is common for some authors to labour in articulating the view any root cause or function of bird homosexuality is poorly understood.

Hypotheses contrived in an attempt to explain the behaviour – homosexuality in birds – typically diverge from one another, further exacerbating an apparent perception in the concerned scientific communities knowledge's quest to realise bird homosexuality remains elusive as an objective. Some authors posit the behaviours are a result of any bird demonstrably homosexual being less inclined to rear young, while other authors posit the timing of emergence from the egg is a factor.

In 1977, The New York Times also reported on a colony of lesbian seagulls "off [the] coast of California." Selected birds from the full list

Barn owlBagemihl (1999) pages 632-5 Cassowary Black swan ChickenBagemihl (1999) pages 83 Common gullBagemihl (1999) pages 544-8 EmuBagemihl (1999) page 621-6 Greylag gooseHubert (1993) House sparrowBagemihl (1999) pages 602-5 Kestrel King penguin365 Gay.com (2005) MallardBagemihl (1999) pages 491-5 Ostrich RavenBagemihl (1999) pages 606-10 Rock doveBagemihl (1999) page 639

Fish

Amazon mollyBagemihl (1999), page 37 Blackstripe topminnowBagemihl (1999), pages 658, 664 Bluegill sunfish Char Grayling European bitterlingBagemihl (1999), page 658 Green swordtail Guiana leaffishBagemihl (1999), page 664 Houting whitefish Jewel cichlidBagemihl (1999), pages 658, 665 Least darter (Microperca punctulata) Mouthbreeding fish sp. Salmon spp.Bagemihl (1999), pages 232, 233, 244 Southern platyfish Ten-spined stickleback Three-spined stickleback

Reptiles

The all-female Whiptail lizard species Aspidoscelis neomexicanus (center), which reproduces via parthenogenesis, is shown flanked by two sexual species having males, A. inornatus (left) and A. tigris (right). Research has shown that simulated mating behavior increases fertility for Aspidoscelis neomexicanus. One female lies on top of another, playing the role of the male, the lizard that was on bottom has larger eggs, in most cases. The lizards switch off this role each mating season.LeVay, (19 September 2007)

American alligatorVilet (2000), page 401 (page 19 in PDF) Anole sp.Bagemihl (1999), page 657 Bearded dragon Blue-tailed day gecko (Phelsuma cepediana)Budzinski, R.-M. (1997) Homosexuelles Verhalten bei Geckos der Gattung Phelsuma. Sauria 19 (3): 33-34 Broad-headed skink Checkered whiptail lizardBagemihl (1999), page 657, 658 Chihuahuan spotted whiptail lizard Common ameiva Common garter snake Cuban green anole Desert grassland whiptail lizard Desert tortoiseBagemihl (1999), pages 232, 664 Eastern fence lizard Five-lined skink Gold dust day gecko (Phelsuma laticauda) Gopher (pine) snake Green anole Inagua curlytail lizard Jamaican giant anole Laredo striped whiptail lizard Largehead anole Mourning geckoBagemihl (1999), pages 663–664 Plateau striped whiptail lizard Red diamond rattlesnake Red-tailed skink Seychelles giant tortoise Side-blotched lizard Speckled rattlesnake Spectacled Caiman Water moccasin Western rattlesnake (Crotalus viridis) Western banded gecko Whiptail lizard spp. Wood turtle Blue-tongued skink

Amphibians

Appalachian woodland salamanderBagemihl (1999), pages 657, 658 Black-spotted frogBagemihl (1999), pages 243, 664 Mountain dusky salamander Tengger desert toad

Insects

Male homosexuality has been inferred in several species of dragonflies. A survey of damsel and dragonflies reveals characteristic cloacal pincher mating damage in 20–80 percent of the males, indicating a fairly high occurrence of sexual coupling between males.Dunkle (1991)Young, L.C., et al. (2008)

Alfalfa weevilBagemihl (1999), page 666 Australian parasitic wasp sp. Bean weevil sp. Bedbug and other bug spp.Tatarnic1 et al., 22 March 2006Bagemihl (1999) page 660 Blister beetle spp.Bagemihl (1999) page 667 Blowfly Broadwinged damselfly sp.Bagemihl (1999) pages 704, 713 Cabbage (small) white (butterfly) Checkerspot butterflyBagemihl (1999) pages 150, 232, 236, 246 Club-tailed dragonfly spp.Bagemihl (1999) pages 33–34, 196, 217, 219, 232 Cockroach spp.Bagemihl (1999) page 668 Codling moth Common skimmer dragonfly spp. Creeping water bug sp.Bagemihl (1999) page 666 CutwormBagemihl (1999) page 595 Digger beeBagemihl (1999) pages 9, 649, 665 Dragonfly spp. Eastern giant ichneumon wasp Eucalyptus longhorned borer Field cricket sp.Bagemihl (1999) page 658 Flour beetleOut magazine , By The Numbers sourced to the Journal of Evolutionary Biology; February 2009. Accessed 2009-01-17. Fruit fly spp.Bagemihl (1999) page 3 Glasswing butterfly Hypoponera opacior ant Grape borer Green lacewingBagemihl (1999) pages 666, 660 Hen flea House flyBagemihl (1999) pages 661–2 Ichneumon wasp sp. Japanese scarab beetleBagemihl (1999) page 661 Larch bud moth Large milkweed bug Large white Leek moth Long-legged fly spp. Mazarine blue Mexican white (butterfly) Midge sp.Bagemihl (1999), pages 661–2 Migratory locustBagemihl (1999), page 659 Monarch butterfly Narrow-winged damselfly spp. Parsnip leaf miner Peach moth Pomace fly Queen butterfly Red ant sp. Red flour beetle Rice moth Reindeer warble fly (Hypoderma tarandi) Rose chafer (Macrodactylus subspinosus) Rove beetle spp. Scarab beetle (melolonthine)Bagemihl (1999), page 661 Screwworm fly Southeastern blueberry bee Southern green stink bug Southern masked chafer Southern one-year canegrub Spreadwinged damselfly spp. Spruce budworm moth Stable fly sp. Stag beetle spp. Tsetse fly Tropical tasar silkmoth Vine moth Water boatman bug Water strider spp.

Other invertebrates

Blood-flukeZimmer (2000) Box crabBagemihl (1999) page 657 Harvestman sp.Bagemihl (1999) pages 236, 704, 713 Hawaiian orb-weaver (spider) Incirrate octopus spp. Jumping spiders Mite sp. Spiny-headed wormBagemihl (1999), pages 668, 667

List of animals displaying homosexual behavior

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