Editing Homosexual behavior in animals (section)

== {{anchor|Some selected species and groups}} Some select species and groups==
{{See also|List of animals displaying homosexual behavior}}

===Birds===
{{See also|List of birds displaying homosexual behavior|Seabird breeding behavior#Same-sex pairing}}

====Black swans====
[[File:Black Swans.jpg|right|thumb|Male [[Black swan|black swans]] (''Cygnus atratus'')]]

An estimated one-quarter of all [[black swan]] pairings are of males. They steal nests, or form temporary threesomes with females to obtain eggs, driving away the female after she lays the eggs. The males spent time in each other's society, guarded the common territory, performed greeting ceremonies before each other, and (in the reproductive period) pre-marital rituals, and if one of the birds tried to sit on the other, an intense fight began.<ref name="ES" /><ref>{{cite journal | last = Braithwaite |first=L. W. | year = 1970 | title = The Black Swan | journal = Australian Natural History | volume = 16 | pages = 375–379 }}</ref> More of their [[swan|cygnet]]s survive to adulthood than those of different-sex pairs, possibly due to their superior ability to defend large portions of land. The same reasoning has been applied to male [[flamingo]] pairs raising chicks.<ref name=Bagemihl/>{{rp|487–491}}<ref name="Oslo gay animal show draws crowds">{{cite news| title=Oslo gay animal show draws crowds| work=[[BBC News]]| date=19 October 2006| url=http://news.bbc.co.uk/2/hi/europe/6066606.stm| access-date = 2009-06-15}}</ref>

====Albatrosses====
Female [[Laysan albatross]]es, on the north-western tip of the island of Oahu, Hawaii, form pairs for co-growing offspring. On the observed island, the number of females considerably exceeds the number of males (59% N=102/172), so 31% of females, after mating with males, create partnerships for hatching and feeding chicks. Compared to male-female couples, female-female partnerships have a lower hatching rate (87% vs 41%) and lower overall [[reproductive success]] (67% vs 31%).<ref>{{cite journal | vauthors = Young LC, Zaun BJ, Vanderwerf EA | title = Successful same-sex pairing in Laysan albatross | journal = Biology Letters | volume = 4 | issue = 4 | pages = 323–5 | date = August 2008 | pmid = 18505710 | pmc = 2610150 | doi = 10.1098/rsbl.2008.0191 }}</ref>

Warming waters from [[climate change]] have led to increased foraging times and thus increased mortality among female [[black-browed albatross]]es on the [[Antipodes Islands]] in [[New Zealand]]. The skewed gender imbalance has led to many male albatrosses forming homosexual relationships. Male-male pairs now comprise between 2–5% of the albatross population on the islands.<ref>{{Cite news|last=Frost|first=Natasha|date=2021-11-29|title=Climate Change Is Driving Some Albatrosses to 'Divorce,' Study Finds|language=en-US|work=The New York Times|url=https://www.nytimes.com/2021/11/29/world/asia/albatross-climate-change.html|access-date=2021-11-29|issn=0362-4331}}</ref><ref>{{Cite web|date=2021-11-24|title=Climate crisis pushes albatross 'divorce' rates higher – study|url=https://www.theguardian.com/environment/2021/nov/24/climate-crisis-pushes-albatross-divorce-rates-higher-study|access-date=2021-11-29|website=The Guardian|language=en}}</ref>

==== Blue ducks ====
In 2009, a UK-based [[captive breeding]] program for [[blue duck]]s (involving two males and one female) was derailed when the two males paired with each other instead of with the female that they were assigned to mate with.<ref>{{Cite web|last=Lite|first=Jordan|title=Gay ducks derail repopulation plan|url=https://blogs.scientificamerican.com/extinction-countdown/gay-ducks-derail-repopulation-plan/|access-date=2021-12-04|website=Scientific American Blog Network|language=en}}</ref>

====Ibises====
{{main|American white ibis#Breeding and lifespan}}
Research has shown that the environmental pollutant [[methylmercury]] can increase the prevalence of homosexual behavior in male [[American white ibis]]. The study involved exposing chicks in varying dosages to the chemical and measuring the degree of homosexual behavior in adulthood. The results discovered was that as the dosage was increased the likelihood of homosexual behavior also increased. The endocrine blocking feature of mercury has been suggested as a possible cause of sexual disruption in other bird species.<ref>{{cite journal|journal=Nature|title=Mercury causes homosexuality in male ibises|last1=Milton|first1=Joseph| name-list-style = vanc |doi=10.1038/news.2010.641|date=1 December 2010}}</ref><ref>{{cite journal | vauthors = Frederick P, Jayasena N | title = Altered pairing behaviour and reproductive success in white ibises exposed to environmentally relevant concentrations of methylmercury | journal = Proceedings. Biological Sciences | volume = 278 | issue = 1713 | pages = 1851–7 | date = June 2011 | pmid = 21123262 | pmc = 3097836 | doi = 10.1098/rspb.2010.2189 }}</ref>

====Mallards====
{{main|Mallard#Breeding}}
[[File:Couple of two male mallard ducks - homosexual Anas platyrhynchos - Moenchbruch - Mönchbruch - May 3rd 2013 - 01.jpg|thumb|Two male [[mallard]]s (''Anas platyrhynchos'')]]

[[Mallard]]s form male-female pairs only until the female lays eggs, at which time the male leaves the female. Mallards have rates of male-male sexual activity that are unusually high for birds, in some cases, as high as 19% of all pairs in a population.<ref name=Bagemihl/>{{Rp|page=493}} [[Kees Moeliker]] of the [[Natural History Museum Rotterdam]] has observed one male mallard engage in homosexual [[necrophilia]].<ref>{{cite journal| vauthors = Moeliker CW |title=The First Case of Homosexual Necrophilia in the Mallard ''Anas platyrhynchos'' (Aves: Anatidae)|journal=Deinsea|volume=8|issue=2001|pages=243–247|date=9 November 2001|url=http://www.hetnatuurhistorisch.nl/fileadmin/user_upload/documents-nmr/Publicaties/Deinsea/Deinsea_08/Deinsea_8_15_Moeliker_.pdf |access-date=6 October 2014}}</ref>

====Penguins====
{{further|Penguin#Behaviour}}
Penguins have been observed to engage in homosexual behaviour since at least as early as 1911. [[George Murray Levick]], who documented this behaviour in [[Adélie penguin]]s at [[Cape Adare]], described it as "depraved". The report was considered too shocking for public release at the time, and was suppressed. The only copies that were made available privately to researchers had the English text partly written in Greek letters, to prevent this knowledge becoming more widely known. The report was unearthed only a century later, and published in ''[[Polar Record]]'' in June 2012.<ref>{{cite web|url=http://www.abc.net.au/news/2012-06-10/explorer27s-study-of-sexually-depraved-penguins-unearthed/4062488|title=Unearthed study on 'sexual depravity' in penguins | date=10 June 2012|website=abc.net.au|access-date=25 March 2018}}</ref><ref>{{cite journal |last1=Russell |first1=Douglas G. D. |last2=Sladen |first2=William J. L. |last3=Ainley |first3=David G. |title=Dr. George Murray Levick (1876–1956): unpublished notes on the sexual habits of the Adélie penguin |journal=Polar Record |date=2012 |volume=48 |issue=4 |pages=387–393 |doi=10.1017/S0032247412000216|bibcode=2012PoRec..48..387R |s2cid=146584734 }}</ref>

In early February 2004, ''[[The New York Times]]'' reported that [[Roy and Silo]], a male pair of [[chinstrap penguin]]s in the [[Central Park Zoo]] in [[New York City]], had successfully hatched and fostered a female chick from a fertile egg they had been given to incubate.<ref name="Love That Dare Not Squeak">{{cite news| last =Smith| first =Dinitia | name-list-style = vanc | title=Love That Dare Not Squeak Its Name| newspaper=The New York Times| date=February 7, 2004| url=https://query.nytimes.com/gst/abstract.html?res=FA0C1EF83A5F0C748CDDAB0894DC404482| access-date = 2007-09-10}}</ref> Other [[penguin]]s in New York zoos have also been reported to have formed same-sex pairs.<ref name="They're in love. They're gay">{{cite web|title= They're in love. They're gay. They're penguins... And they're not alone.|publisher= [[Columbia University]]|agency= Columbia News Service|date= June 10, 2002|url= http://www.timelessspirit.com/SEPT04/cristina.shtml|url-status=dead|archive-url= https://web.archive.org/web/20090123213518/http://www.timelessspirit.com/SEPT04/cristina.shtml|archive-date = January 23, 2009}}</ref><ref>[http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2004/02/07/MNG3N4RAV41.DTL "Central Park Zoo's gay penguins ignite debate"], 2002-02-07, ''San Francisco Chronicle''</ref>

In Odense Zoo in Denmark, a pair of male king penguins adopted an egg that had been abandoned by a female, proceeding to incubate it and raise the chick.<ref>{{cite news|title=Denmark's Gay Penguins Become Fathers|url=http://www.huffingtonpost.com/2012/11/09/denmark-gay-penguins-fathers_n_2104190.html |newspaper=Huffington Post|date=November 11, 2012}}</ref><ref>{{cite news|title=Gay Penguins Become Dads|url=https://www.buzzfeed.com/stacylambe/gay-penguins-become-dads|newspaper=BuzzFeed|date=November 9, 2012}}</ref>
Zoos in [[Japan]] and [[Germany]] have also documented homosexual male penguin couples.<ref name="DW">{{cite news |url=http://www.dw.com/en/cold-shoulder-for-swedish-seductresses/a-1484083 |title=Cold Shoulder for Swedish Seductresses &#124; Germany|publisher=Deutsche Welle |date=2005-02-10 |access-date=2010-11-17}}</ref><ref name="CBC">{{cite news| url=https://www.cbc.ca/news/world/gay-penguin-couple-adopts-abandoned-egg-in-german-zoo-1.794702 | publisher=CBC News | title=Gay penguin couple adopts abandoned egg in German zoo | date=2009-06-05}}</ref> The couples have been shown to build nests together and use a stone as a substitute for an egg. Researchers at [[Rikkyo University]] in [[Tokyo]] found 20 homosexual pairs at 16 major aquariums and zoos in Japan.

The [[Bremerhaven Zoo]] in Germany attempted to encourage reproduction of endangered [[Humboldt penguin]]s by importing females from Sweden and separating three male pairs, but this was unsuccessful. The zoo's director said that the relationships were "too strong" between the homosexual pairs.<ref>{{cite web|url=http://www.ananova.com/news/story/sm_1275591.html |title=Ananova Article on "Tempting Gay Penguins Straight" |publisher=Ananova.com |access-date=2010-11-17}}</ref> German gay groups protested at this attempt to break up the male-male pairs<ref>{{cite web |url=http://www.ananova.com/news/story/sm_1284769.html |title=Followup Ananova Article on German authorities stopping trying to change the penguins' sexual orientation, after GLBTQI organizations protest |publisher=Ananova.com |access-date=2010-11-17 |archive-url=https://web.archive.org/web/20090208215419/http://www.ananova.com/news/story/sm_1284769.html |archive-date=2009-02-08 |url-status=dead }}</ref> but the zoo's director was reported as saying "We don't know whether the three male pairs are really homosexual or whether they have just bonded because of a shortage of females ... nobody here wants to forcibly separate homosexual couples."<ref>{{cite news| url=http://news.bbc.co.uk/1/hi/world/europe/4264913.stm | work=BBC News | title=Gay outrage over penguin sex test | date=2005-02-14 | access-date=2010-05-04}}</ref>

A pair of male [[Magellanic penguin]]s at the [[San Francisco Zoo]] shared a burrow for six years and raised a surrogate chick; the pair split when the male of a pair in the next burrow died and the female sought a new mate.<ref>{{cite news|url=http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2009/07/14/BAUS18NTE7.DTL |title=Widow a wedge between zoo's male penguin pair |newspaper=San Francisco Chronicle |date=2009-07-14 |access-date=2010-11-17 |first=Meredith |last=May| name-list-style = vanc }}</ref>

Buddy and Pedro, a pair of male [[African penguin]]s, were separated by the [[Toronto Zoo]] to mate with female penguins in 2011.<ref>{{Citation |last= McCormack|first= Simon| name-list-style = vanc |date=14 November 2011 |title=Gay Penguins Reunion: Buddy And Pedro Will Be Back Together By Spring |work=Gay Voices |publisher=[[The Huffington Post]] |url=http://www.huffingtonpost.com/2011/11/14/gay-penguin-reunion_n_1093298.html |access-date=16 November 2011}}</ref><ref name="GPBT">{{cite news| url=https://www.cbc.ca/news/canada/toronto/same-sex-penguin-pair-pursue-female-partners-1.1004938 | publisher=CBC News | title=Same-sex penguin pair pursue female partners | date=2011-12-12}}</ref> Buddy has since paired off with a female.<ref name="GPBT"/>

Suki and Chupchikoni are two female African penguins that pair bonded at the [[Ramat Gan Safari]] in Israel in 2013. Chupchikoni was assumed to be male until her blood was tested.<ref>{{cite news|last=Schuster|first=Ruth| name-list-style = vanc |title=Lesbian Penguins Shack Up at Israeli Zoo|url=http://forward.com/articles/189552/lesbian-penguins-shack-up-at-israeli-zoo/|newspaper=The Jewish Daily Forward|date=December 19, 2013}}</ref>

Jumbs and Kermit, two male Humboldt penguins at [[Wingham Wildlife Park]], were given an egg from heterosexual couple Hurricane and Isobel. The egg failed to hatch. However, they were given another abandoned egg from the same couple which successfully hatched on 12 April 2014.<ref name="penguin">[[Wingham Wildlife Park]]</ref>

As of 2018, two female King penguins at [[Kelly Tarlton's Sea Life Aquarium|Kelly Tarltons]] in [[Auckland]], New Zealand, called Thelma and Louise (named after the [[Thelma & Louise|1991 film]]) have been in a relationship for eight years, when most of the other eligible penguins switch partners each mating season, regardless of their orientation. The two penguins were both taking care of an egg that Thelma hatched, but is unknown whether it was fertilized.<ref>{{Cite news|url=https://www.newshub.co.nz/home/new-zealand/2018/12/auckland-s-gay-penguin-couple-prepare-for-special-christmas-bundle-of-joy.html|title=Auckland's gay penguin couple prepare for special Christmas bundle of joy|work=Newshub|access-date=2018-12-24|language=en|archive-url=https://web.archive.org/web/20181224143719/https://www.newshub.co.nz/home/new-zealand/2018/12/auckland-s-gay-penguin-couple-prepare-for-special-christmas-bundle-of-joy.html|archive-date=2018-12-24|url-status=dead}}</ref>

[[Sphen and Magic]], two male [[gentoo penguin|gentoo penguins]] in [[Sea Life Sydney Aquarium]], paired in 2018 and went on to raise two chicks, Lara (formerly Sphengic) and Clancy.<ref>{{Cite news |last=Bowles |first=Nellie |date=2019-01-15 |title=The Gay Penguins of Australia |url=https://www.nytimes.com/2019/01/15/style/gay-penguins-australia.html |access-date=2024-08-22 |work=[[The New York Times]] |language=en-US |issn=0362-4331}}</ref><ref>{{Cite news |last=Press |first= |date=2024-08-21 |title=When globally famous gay penguin Sphen died in Sydney, his partner began to sing |url=https://www.theguardian.com/australia-news/article/2024/aug/22/when-globally-famous-gay-penguin-sphen-died-in-sydney-his-partner-began-to-sing |access-date=2024-08-22 |work=[[The Guardian]] |language=en-GB |issn=0261-3077}}</ref> Sphen died in 2024.<ref>{{Cite web |date=2024-08-22 |title=Gay penguin Sphen dies in Australian aquarium |url=https://www.dw.com/en/gay-penguin-sphen-dies-in-australian-aquarium/a-70011352 |access-date=2024-08-22 |website=[[Deutsche Welle]] |language=en}}</ref>

In September 2018 at [[Odense Zoo]] in Denmark, a male penguin couple took a chick from a heterosexual couple while they were swimming. Zoo staff speculated that the couple saw the biological parents as neglectful of the chick. The biological parents later confronted the couple and zoo staff returned the chick to them.<ref>{{Cite web |last=Kacala |first=Alexander |date=2018-09-27 |title=Gay penguins 'kidnap' chick from straight parents at Denmark zoo |url=https://www.nbcnews.com/feature/nbc-out/gay-penguins-kidnap-chick-straight-parents-denmark-zoo-n913611 |access-date=2024-08-22 |website=[[NBC News]] |language=en}}</ref>

Marama and Rocky, two female gentoo penguins at [[Sea Life London Aquarium]], had an "incredibly strong bond" for five years prior to adopting a chick who was born in June 2019.<ref>{{Cite web |last=Konstantinides |first=Anneta |title=A same-sex penguin couple at a London aquarium become mothers for the first time after adopting a chick |url=https://www.businessinsider.com/same-sex-penguin-couple-adopt-first-chick-london-aquarium-2019-7 |access-date=2024-08-22 |website=[[Business Insider]] |language=en-US}}</ref> The chick was intentionally not gendered and was given a [[Gender neutrality|gender-neutral]] purple band for identification purposes.<ref>{{Cite news |last=Gawronski |first=Quinn |date=2019-09-10 |title=Gay penguins at London aquarium are raising 'genderless' chick |url=https://www.nbcnews.com/feature/nbc-out/gay-penguins-london-aquarium-are-raising-genderless-chick-n1052096 |access-date=2024-08-22 |work=[[NBC News]]}}</ref> They were still a couple in 2021.<ref name="SS">{{Cite news |title=Penguins: Same-sex couples formed at London aquarium |url=https://www.bbc.co.uk/news/uk-england-london-57076071 |access-date=2024-08-22 |work=[[BBC News]]}}</ref>

Skipper and Ping, two male penguins at [[Berlin Zoo]], adopted an abandoned egg in July 2019.<ref>{{Cite news |date=2019-08-12 |title=Berlin gay penguins adopt abandoned egg |url=https://www.bbc.co.uk/news/blogs-news-from-elsewhere-49318080 |access-date=2024-08-22 |work=[[BBC News]] |language=en-GB}}</ref>

A female penguin couple named Electra and Viola adopted, incubated and raised an egg from another couple at [[L'Oceanogràfic]] in [[Valencia]] in 2020.<ref>{{Cite web |last=Silva |first=Cynthia |date=2020-08-26 |title=Lesbian penguin 'super moms' welcome chick at Spanish aquarium |url=https://www.nbcnews.com/feature/nbc-out/lesbian-penguin-super-moms-welcome-chick-spanish-aquarium-n1238072 |access-date=2024-08-22 |website=[[NBC News]] |language=en}}</ref>

A second same-sex female couple, Marmalade and Chickpea, formed at Sea Life London during the 2021 mating season.<ref name="SS" />

====Vultures====
In 1998, two male [[griffon vulture]]s named Dashik and Yehuda, at the [[Jerusalem Biblical Zoo]], engaged in "open and energetic sex" and built a nest. The keepers provided the couple with an artificial egg, which the two parents took turns incubating, and 45 days later, the zoo replaced the egg with a baby vulture. The two male vultures raised the chick together.<ref>{{cite news |url=https://www.independent.co.uk/news/gay-vulture-couple-raise-surrogate-chicks-1110120.html |title=Gay vulture couple raise surrogate chicks | first = Eric | last = Silver | name-list-style = vanc |newspaper=The Independent |date=2 August 1999 |access-date=2009-09-21 | location=London }}</ref> A few years later, however, Yehuda became interested in a female vulture that was brought into the aviary. Dashik became depressed, and was eventually moved to the zoological research garden at [[Tel Aviv University]] where he too set up a nest with a female vulture.<ref>{{cite news|url=http://www.haaretz.com/hasen/spages/1115739.html|title='Gay' vulture couple split up at Jerusalem zoo, then become fathers|first=Jonathan|last=Lis|name-list-style=vanc|newspaper=[[Haaretz]]|date=21 September 2009|access-date=2009-09-21|archive-date=16 June 2013|archive-url=https://web.archive.org/web/20130616033627/http://www.haaretz.com/print-edition/news/gay-vulture-couple-split-up-at-jerusalem-zoo-then-become-fathers-1.7562|url-status=dead}}</ref>

Two male vultures at the [[Allwetter Zoo]] in [[Münster|Muenster]] built a nest together, although they were picked on and their nest materials were often stolen by other vultures. They were eventually separated to try to promote breeding by placing one of them with female vultures, despite the protests of German homosexual groups.<ref>{{cite web |url=http://entertainment.stv.tv/showbiz/209259-gay-vultures-split-up-to-go-straight/ |title=Gay vultures split up to go straight &#124; Showbiz: Latest News &#124; STV Entertainment |publisher=Entertainment.stv.tv |access-date=2010-11-17 |archive-date=21 November 2010 |archive-url=https://web.archive.org/web/20101121075904/http://entertainment.stv.tv/showbiz/209259-gay-vultures-split-up-to-go-straight/ |url-status=dead }}</ref>

====Pigeons====
{{further|Pigeon#Courtship and reproduction}}
Both male and female [[pigeon]]s sometimes exhibit homosexual behavior. In addition to sexual behavior, same-sex pigeon pairs will build nests, and hens will lay (infertile) eggs and attempt to incubate them.<ref>{{Cite journal|last1=Jankowiak|first1=Łukasz|last2=Tryjanowski|first2=Piotr|last3=Hetmański|first3=Tomasz|last4=Skórka|first4=Piotr|date=2018-01-26|title=Experimentally evoked same-sex sexual behaviour in pigeons: better to be in a female-female pair than alone|journal=Scientific Reports|language=en|volume=8|issue=1|page=1654|doi=10.1038/s41598-018-20128-3|pmid=29374281|issn=2045-2322|pmc=5785962|bibcode=2018NatSR...8.1654J}}</ref>

===Mammals===
{{see also|List of mammals displaying homosexual behavior|Animal sexual behaviour#Mammals}}

===={{anchor|Amazon_Dolphin}}Amazon dolphins====
The [[Amazon river dolphin]] or [[boto]] has been reported to form up in bands of 3–5 individuals engaging in sexual activity. The groups usually comprise young males and sometimes one or two females. Sex is often performed in non-reproductive ways, using snout, flippers and genital rubbing, without regard to gender.<ref name=Bagemihl/>{{rp|339–348}} In captivity, they have been observed to sometimes perform homosexual and heterosexual penetration of the [[Blowhole (biology)|blowhole]], a hole homologous with the [[nostril]] of other mammals, making this the only known example of nasal sex in the animal kingdom.<ref name=Bagemihl/>{{rp|339–348}}<ref>Sylvestre, J.-P. (Some Observations on Behavior of Two Orinoco Dolphins (Inia geoffrensis humboldtiaba [Pilleri and Gihr 1977]), in Captivity, at Duisburg Zoo. ''Aquatic mammals'' no 11, pp. 58–65 [http://www.aquaticmammalsjournal.org/share/AquaticMammalsIssueArchives/1985/Aquatic_Mammals_11_2/Sylvestre.pdf article] {{Webarchive|url=https://web.archive.org/web/20161022010800/http://www.aquaticmammalsjournal.org/share/aquaticmammalsissuearchives/1985/aquatic_mammals_11_2/sylvestre.pdf |date=22 October 2016 }}</ref> The males will sometimes also perform sex with males from the [[tucuxi]] species, a type of small [[porpoise]].<ref name=Bagemihl/>{{rp|339–348}}

====American bisons====
[[File:American bison k5680-1.jpg|thumb|The American bison is a [[bovine]] [[mammal]] which displays homosexual behavior.]]
{{further|American bison#Behavior and ecology}}
Courtship, mounting, and full [[anal sex|anal penetration]] between bulls has been noted to occur among [[American bison]]. The [[Mandan]] nation {{lang|mhq|[[Okipa]]}} festival concludes with a ceremonial enactment of this behavior, to "ensure the return of the buffalo in the coming season".<ref name="Left-Handed Bears & Androgynous">{{cite news|last=Bagemihl |first=Bruce | name-list-style = vanc |title=Left-Handed Bears & Androgynous Cassowaries: Homosexual/transgendered animals and indigenous knowledge |work=[[Whole Earth Review|Whole Earth Magazine]] |date=May 2000 |url=http://www.wholeearthmag.com/ArticleBin/338.html |access-date=13 December 2013 |url-status=dead |archive-url=https://web.archive.org/web/20000815195419/http://www.wholeearthmag.com/ArticleBin/338.html |archive-date=August 15, 2000 |via=[[Internet Archive]]}}</ref> Also, mounting of one female by another (known as "[[Bulling (cattle)|bulling]]") is extremely common among [[cattle]]. The behaviour is hormone driven and synchronizes with the emergence of estrus (heat), particularly in the presence of a bull.

====Bats====
[[File:Homosexual-Fellatio-Erect-Penis-Licking-between-Male-Bonin-Flying-Foxes-Pteropus-pselaphon-pone.0166024.s002.ogv|thumb|Two male [[Bonin flying fox]]es (''Pteropus pselaphon'') performing [[fellatio]] on each other<ref name="Sugita2016"/>]]

More than 20 species of bat have been documented to engage in homosexual behavior.<ref name="Riccucci2011"/><ref name="Sugita2016">{{cite journal | vauthors = Sugita N | title = Homosexual Fellatio: Erect Penis Licking between Male Bonin Flying Foxes Pteropus pselaphon | journal = PLOS ONE | volume = 11 | issue = 11 | pages = e0166024 | date = Nov 2016 | pmid = 27824953 | pmc = 5100941 | doi = 10.1371/journal.pone.0166024 | bibcode = 2016PLoSO..1166024S | doi-access = free }}</ref> Bat species that have been observed engaging in homosexual behavior in the wild include:<ref name="Riccucci2011"/>
{{columns-list|colwidth=30em|
* the [[grey-headed flying fox]] (''Pteropus poliocephalus'')
* the [[Bonin flying fox]] (''Pteropus pselaphon'')<ref name="Sugita2016"/>
* the [[Indian flying fox]] (''Pteropus giganteus'')
* [[Rafinesque's big-eared bat]] (''Corynorhinus rafinesquii'')
* the [[common bent-wing bat]] (''Miniopterus schreibersii'')
* the [[serotine bat]] (''Eptesicus serotinus'')
* [[Bechstein's bat]] (''Myotis bechsteinii'')
* the [[long-fingered bat]] (''Myotis capaccinii'')
* [[Daubenton's bat]] (''Myotis daubentonii'')
* the  [[little brown bat]] (''Myotis lucifugus'')
* the [[greater mouse-eared bat]] (''Myotis myotis'')
* the [[whiskered bat]] (''Myotis mystacinus'')
* [[Natterer's bat]] (''Myotis nattereri'')
* the [[common noctule]] (''Nyctalus noctula'')
* [[Leisler's bat]] (''Nyctalus leisleri'')
* the [[common pipistrelle]] (''Pipistrellus pipistrellus'')
* the [[brown long-eared bat]] (''Plecotus auritus'')
* the [[barbastelle]] (''Barbastella barbastellus'')
* the [[greater horseshoe bat]] (''Rhinolophus ferrumequinum'')
* the [[lesser horseshoe bat]] (''Rhinolophus hipposideros'')}}

Bat species that have been observed engaging in homosexual behavior in captivity include the [[Livingstone's fruit bat|Comoro flying fox]] (''Pteropus livingstonii''), the [[Rodrigues flying fox]] (''Pteropus rodricensis'') and the [[common vampire bat]] (''Desmodus rotundus'').<ref name="Riccucci2011"/>

Homosexual behavior in bats has been categorized into 6 groups: mutual homosexual grooming and licking, homosexual masturbation, homosexual play, homosexual mounting, coercive sex, and cross-species homosexual sex.<ref name="Riccucci2011"/><ref name="Sugita2016"/>

In the wild, the [[grey-headed flying fox]] (''Pteropus poliocephalus'') engages in [[Social grooming|allogrooming]] wherein one partner licks and gently bites the chest and wing membrane of the other partner. Both sexes display this form of mutual homosexual grooming and it is more common in males. Males often have erect penises while they are mutually grooming each other. Like opposite-sex grooming partners, same-sex grooming partners continuously utter a "pre-copulation call", which is described as a "pulsed grating call", while engaged in this activity.<ref name="Riccucci2011"/><ref name="Sugita2016"/>

In wild [[Bonin flying fox]]es (''Pteropus pselaphon''), males perform fellatio or 'male-male genital licking' on other males. Male–male genital licking events occur repeatedly several times in the same pair, and reciprocal genital licking also occurs. The male-male genital licking in these bats is considered a sexual behavior. Allogrooming in Bonin flying foxes has never been observed, hence the male-male genital licking in this species does not seem to be a byproduct of allogrooming, but rather a behavior of directly licking the male genital area, independent of allogrooming.<ref name="Sugita2016"/> In captivity, same-sex genital licking has been observed among males of the [[Livingstone's fruit bat|Comoro flying fox]] (''Pteropus livingstonii'') as well as among males of the [[common vampire bat]] (''Desmodus rotundus'').<ref name="Riccucci2011"/><ref name="Sugita2016"/>

In wild [[Indian flying fox]]es (''Pteropus giganteus''), males often mount one another, with erections and thrusting, while play-wrestling.<ref name="Riccucci2011"/> Males of the [[long-fingered bat]] (''Myotis capaccinii'') have been observed in the same position of male-female mounting, with one gripping the back of the other's fur. A similar behavior was also observed in the [[common bent-wing bat]] (''Miniopterus schreibersii'').<ref name="Riccucci2011"/>

In wild [[little brown bat]]s (''Myotis lucifugus''), males often mount other males (and females) during late autumn and winter, when many of the mounted individuals are [[torpor|torpid]].<ref name="Riccucci2011"/> 35% of matings during this period are homosexual.<ref name="Myotis lucifugusADW">{{cite journal| vauthors = Havens A |editor1-last=Dewey|editor1-first=Tanya|editor2-last=Shefferly|editor2-first=Nancy|title=Myotis lucifugus|journal=Animal Diversity Web|date=2006|url=http://animaldiversity.org/accounts/Myotis_lucifugus/}}</ref> These coercive copulations usually include ejaculation and the mounted bat often makes a typical copulation call consisting of a long squawk.<ref name="Riccucci2011"/> Similarly, in [[Hibernaculum (zoology)|hibernacula]] of the [[common noctule]] (''Nyctalus noctula''), active males were observed to wake up from lethargy on a warm day and engage in mating with lethargic males and (active or lethargic) females. The lethargic males, like females, called out loudly and presented their buccal glands with opened mouth during copulation.<ref name="Riccucci2011"/>

Vesey-Fitzgerald (1949) observed homosexual behaviours in all 12 British bat species known at the time: "Homosexuality is common in the spring in all species, and, since the males are in full possession of their powers, I suspect throughout the summer...I have even seen homosexuality between [[Natterer's bat|Natterer's]] and [[Daubenton's bat]]s (''Myotis nattereri'' and ''M. daubentonii'')."<ref name="Riccucci2011"/>

====Bottlenose dolphins====
{{see also|Animal sexual behavior#Bottlenose dolphins|Bottlenose dolphin#Life history}}
Dolphins of several species engage in homosexual acts, though it is best studied in the [[bottlenose dolphin]]s.<ref name=Bagemihl/>{{page needed|date=May 2016}} Sexual encounters between females take the shape of "beak-genital propulsion", where one female inserts her beak in the genital opening of the other while swimming gently forward.<ref>{{cite journal| vauthors = Norris KS, Dohl TP |title=Behaviour of the Hawaiian spinner dolphin, ''Stenella longirostris''|journal=Fishery Bulletin|year=1980|volume=77|pages=821–849}}</ref> Between males, homosexual behaviour includes rubbing of genitals against each other, which sometimes leads to the males swimming belly to belly, inserting [[dolphin penis|the penis]] in the other's [[genital slit]] and sometimes anus.<ref>{{cite web | vauthors = Wells RS |title=Community structure of Bottlenose Dolphins near Sarasota, Florida|year=1995|series=Paper presented at the 24th International Ethological Conference, Honoluly, Hawaii|url= https://www.researchgate.net/publication/285070874}}</ref>

Janet Mann, [[Georgetown University]] professor of biology and psychology, argues that the strong personal behavior among male dolphin calves is about bond formation and benefits the species in an evolutionary context.<ref>{{cite web|url=http://www.livescience.com/2534-sex-couples-common-wild.html|title=Same Sex Couples Common in the Wild |website=livescience.com|date=16 May 2008 |access-date=25 March 2018}}</ref> She cites studies showing that these dolphins later in life as adults are in a sense bisexual, and the male bonds forged earlier in life work together for protection as well as locating females to reproduce with. Confrontations between flocks of bottlenose dolphins and the related species [[Atlantic spotted dolphin]] will sometimes lead to cross-species homosexual behaviour between the males rather than combat.<ref>{{cite journal| vauthors = Herzing DL, Johnson CM |title=Interspecific Interaction between Spotted Dolphins (''Stenella frontalis'') and Bottlenose Dolphins (''Tursiops truncatus'') in the Bahamas, 1985–1995|journal=Aquatic Mammals|year=1997|volume=23|pages=85–99}}</ref>

====Elephants====
{{further|Elephant#Mating}}
[[African elephant|African]] and [[Asian elephant|Asian]] male elephants will engage in same-sex bonding and mounting. Such encounters are often associated with affectionate interactions, such as kissing, trunk intertwining, and placing trunks in each other's mouths. Male elephants, who often live apart from the general herd, often form "companionships", consisting of an older individual and one or sometimes two younger males with sexual behavior being an important part of the social dynamic. Unlike [[heterosexual]] relations, which are always of a fleeting nature, the relationships between males may last for years. The encounters are analogous to heterosexual bouts, one male often extending his trunk along the other's back and pushing forward with his tusks to signify his intention to mount. Same-sex relations are common and frequent in both sexes, with Asiatic elephants in captivity devoting roughly 45% of sexual encounters to same-sex activity.<ref name=Bagemihl/>{{rp|427–430}}

====Giraffes====
{{further|Giraffe#Necking}}
Male [[giraffe]]s have been observed to engage in remarkably high frequencies of homosexual behavior. After aggressive "necking", it is common for two male giraffes to caress and court each other, leading up to mounting and climax. Such interactions between males have been found to be more frequent than heterosexual coupling.<ref>{{cite journal | vauthors = Coe MJ | year = 1967 | title = "Necking" behavior in the giraffe | journal = Journal of Zoology | volume = 151 | issue =3 | pages = 313–321 | doi=10.1111/j.1469-7998.1967.tb02117.x }}</ref> In one study, up to 94% of observed mounting incidents took place between two males. The proportion of same sex activities varied between 30 and 75%, and at any given time one in twenty males were engaged in non-combative necking behavior with another male. Only 1% of same-sex mounting incidents occurred between females.<ref name=Bagemihl/>{{rp|391–393}}

==== Humpback whales ====
In 2022, photographers captured the first-ever images of [[Humpback whale|humpback whales]] mating, both of which were males, off the coast of [[Maui]]. The whales were observed for 30 minutes, with one whale using its penis to penetrate the genital slit of the other.<ref>{{Cite web |last=Kuta |first=Sarah |title=These Photos Are the First to Show Humpback Whales Mating—and Both Are Males |url=https://www.smithsonianmag.com/smart-news/these-photos-are-the-first-to-show-humpback-whales-mating-and-both-are-males-180983890/ |access-date=2024-03-11 |website=Smithsonian Magazine |language=en}}</ref><ref>{{Cite journal |last1=Stack |first1=Stephanie H. |last2=Krannichfeld |first2=Lyle |last3=Romano |first3=Brandi |date=2024-02-27 |title=An observation of sexual behavior between two male humpback whales |journal=Marine Mammal Science |volume=40 |issue=3 |language=en |doi=10.1111/mms.13119 |issn=0824-0469|doi-access=free |bibcode=2024MMamS..40E3119S |hdl=10072/430033 |hdl-access=free }}</ref>

====Marmots====
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Homosexual behavior is quite common in wild marmots.<ref name=Bagemihl/>{{rp|525–527}} In [[Olympic marmot]]s (''Marmota olympus'') and [[hoary marmot]]s (''Marmota caligata''), females often mount other females as well as engage in other affectionate and sexual behaviors with females of the same species.<ref name=Bagemihl/>{{rp|525–527}} They display a high frequency of these behaviors especially when they are [[estrus|in heat]].<ref name=Bagemihl/>{{rp|525–527}}<ref name="Barash1973">{{cite journal| vauthors = Barash DP|title=The Social Biology of the Olympic Marmot|journal=Animal Behaviour Monographs |date=1973|volume=6|issue=3 |pages=171–245 |doi=10.1016/0003-3472(73)90002-X}}</ref> A homosexual encounter often begins with a greeting interaction in which one female nuzzles her nose on the other female's cheek or mouth, or both females touch noses or mouths. Additionally, a female may gently chew on the ear or neck of her partner, who responds by raising her tail. The first female may sniff the other's genital region or nuzzle that region with her mouth. She may then proceed to mount the other female, during which the mounting female gently grasps the mounted female's dorsal neck fur in her jaws while thrusting. The mounted female arches her back and holds her tail to one side to facilitate their sexual interaction.<ref name=Bagemihl/>{{rp|525–527}}<ref name="Barash1974">{{cite journal| vauthors = Barash DP |title=The social behaviour of the hoary marmot (Marmota caligata)| journal=Anim. Behav.|date=Feb 1974|volume=22 |issue=1| pages=256–61| doi=10.1016/S0003-3472(74)80077-1}}</ref>

====Lions====
{{further|Sexual behavior of lions}}
[[File:Wuppertal - Zoo - Panthera leo 01 (1) ies.webm|thumb|right|Male lions mating]]

Both male and female [[lion]]s have been seen to interact [[animal sexuality|homosexually]].{{refn|<ref name=Bagemihl/>{{rp|302–305}}<ref>In his discussion of lion same-sex relations, Bagemihl is making use of published work by: J.B. Cooper, "An Exploratory Study on African Lions" in ''Comparative Psychology Monographs'' 17:1–48; R.L. Eaton, "The Biology and Social Behavior of Reproduction in the Lion" in Eaton, ed. ''The World's Cats,'' vol. II; pp.3–58; Seattle, 1974; G.B. Schaller, ''The Serengeti Lion''; University of Chicago Press, 1972</ref><ref>{{cite web | last =Srivastav | first =Suvira | name-list-style = vanc | title =Lion, Without Lioness | work =TerraGreen: News to Save the Earth | publisher =Terragreen | date =15–31 December 2001 | url =http://www.teri.res.in/teriin/terragreen/issue3/feature.htm | access-date =2007-09-02 | url-status=dead | archive-url =https://web.archive.org/web/20070914010938/http://www.teri.res.in/teriin/terragreen/issue3/feature.htm | archive-date =14 September 2007 }}</ref>}} Male lions pair-bond for a number of days and initiate homosexual activity with affectionate nuzzling and caressing, leading to mounting and [[pelvic thrusting|thrusting]]. About 8% of mountings have been observed to occur with other males. Pairings between females are held to be fairly common in captivity but have not been observed in the wild.

====Polecats====
[[European polecat]]s (''Mustela putorius'') were found to engage homosexually with non-sibling animals. Exclusive homosexuality with mounting and anal penetration in this solitary species serves no apparent adaptive function.<ref>[[Thierry Lodé]] ''La guerre des sexes chez les animaux'' Eds O Jacob, Paris, 2006.{{ISBN|2-7381-1901-8}}</ref>{{page needed|date=May 2016}}

====Primates====
Same-sex sexual behaviors have been observed in New World monkeys, Old World monkeys, and apes. These behaviors are much more common in Old World monkeys than New World monkeys, and all ape genera have been observed engaging in same-sex sexual behavior. Prosimians have not been observed engaging in same-sex sexual behavior. Same-sex mounting, for instance, has been observed in 16% of New World primate genera. In contrast, 76% of Old World monkey genera contain at least one species that has been observed in male-male mounts, and 70% of genera for female-female mounts. Same-sex mounting has been observed in all ape genera. Same-sex sexual behaviors likely evolved following the divergence of New World monkeys;<ref>{{Cite journal |last1=Pfau |first1=Daniel |last2=Jordan |first2=Cynthia L. |last3=Breedlove |first3=S. Marc |date=2021-08-01 |title=The De-Scent of Sexuality: Did Loss of a Pheromone Signaling Protein Permit the Evolution of Same-Sex Sexual Behavior in Primates? |url=https://doi.org/10.1007/s10508-018-1377-2 |journal=Archives of Sexual Behavior |language=en |volume=50 |issue=6 |pages=2267–2276 |doi=10.1007/s10508-018-1377-2 |pmid=31016493 |s2cid=254251448 |issn=1573-2800|url-access=subscription }}</ref> these behaviors are a conserved trait among Old World monkeys and apes.<ref>{{Citation |last=Dixson |first=Alan |title=Homosexual behaviour in primates |date=2010-08-19 |url=http://dx.doi.org/10.1017/cbo9780511762192.010 |work=Animal Homosexuality |pages=381–400 |access-date=2023-10-22 |publisher=Cambridge University Press|doi=10.1017/cbo9780511762192.010 |isbn=978-0-521-19675-8 |url-access=subscription }}</ref> Among Old World monkeys, same-sex genital interactions are much more common in multi-male systems as opposed to uni-male systems.<ref>{{Cite journal |last1=MacFarlane |first1=Geoff R. |last2=Vasey |first2=Paul L. |date=2016-05-01 |title=Promiscuous primates engage in same-sex genital interactions |url=https://www.sciencedirect.com/science/article/pii/S0376635716300377 |journal=Behavioural Processes |volume=126 |pages=21–26 |doi=10.1016/j.beproc.2016.02.016 |pmid=26930251 |s2cid=39603917 |issn=0376-6357|url-access=subscription }}</ref>

=====Bonobos=====
{{See also|Bonobo#Sociosexual behaviour}}[[File:Bonobo 011.jpg|thumb|right|Two male bonobos]]
[[Bonobo]]s form a [[Matriarchy|matriarchal]] society, unusual among [[ape]]s. They are fully [[Bisexuality|bisexual]]: both males and females engage in hetero- and homosexual behavior, being noted for female–female sex in particular, including between juveniles and adults.<ref name="De_Waal_1995">{{cite journal |last=de Waal |first=Frans B. M. |author-link=Frans de Waal |name-list-style=vanc |date=March 1995 |title=Bonobo Sex and Society: The behavior of a close relative challenges assumptions about male supremacy in human evolution |url=http://www.biolinguagem.com/ling_cog_cult/dewaal_1995_bonobosexsociety.pdf |url-status=dead |journal=[[Scientific American]] |volume=272 |issue=3 |pages=82–88 |bibcode=1995SciAm.272c..82W |doi=10.1038/scientificamerican0395-82 |pmid=7871411 |archive-url=https://web.archive.org/web/20160801020429/http://www.biolinguagem.com/ling_cog_cult/dewaal_1995_bonobosexsociety.pdf |archive-date=1 August 2016 |access-date=10 March 2019}}</ref> Roughly 60% of all bonobo sexual activity occurs between two or more females. While the homosexual bonding system in bonobos represents the highest frequency of homosexuality known in any primate species, homosexuality has been reported for all [[Hominidae|great apes]], as well as a number of other [[primate]] species.{{refn|<ref>{{Cite web |title=Bonobo |url=http://www.colszoo.org/animalareas/aforest/bonobo.html |url-status=dead |archive-url=https://web.archive.org/web/20070817012421/http://www.colszoo.org/animalareas/aforest/bonobo.html |archive-date=17 August 2007 |publisher=[[Columbus Zoo and Aquarium]]}}</ref><ref>{{cite book |last=Dawkins |first=Richard |title=The Ancestor's Tale: A Pilgrimage to the Dawn of Life |title-link=The Ancestor's Tale |publisher=[[Houghton Mifflin]] (US) |year=2004 |isbn=978-1-155-16265-2 |pages=92–93 |chapter=Rendezvous I: Chimpanzees |author-link=Richard Dawkins |name-list-style=vanc}}</ref><ref>{{cite web |last=Laird |first=Courtney |name-list-style=vanc |title=Social Organization |url=http://www.bio.davidson.edu/people/vecase/Behavior/Spring2004/laird/Social%20Organization.htm |url-status=dead |archive-url=https://web.archive.org/web/20110519005633/http://www.bio.davidson.edu/people/vecase/Behavior/Spring2004/laird/Social%20Organization.htm |archive-date=19 May 2011 |website=bio.davidson.edu}}</ref><ref>{{cite journal |vauthors=Stanford CB |year=1998 |title=The social behavior of chimpanzees and bonobos |journal=[[Current Anthropology]] |volume=39 |issue=4 |pages=399–407 |doi=10.1086/204757 |s2cid=8452514}}</ref><ref>{{Cite book |last=Kano |first=Takayoshi |title=The Last Ape: Pygmy Chimpanzee Behavior and Ecology |publisher=[[Stanford University Press]] |year=1992 |isbn=9780804716123 |name-list-style=vanc}}</ref>}}

Dutch [[Primatology|primatologist]] [[Frans de Waal]], who extensively observed and filmed bonobos, believed that sexual activity is the bonobo's way of avoiding conflict. Anything that arouses the interest of more than one bonobo at a time, not just food, tends to result in sexual contact. If two bonobos approach a cardboard box thrown into their enclosure, they will briefly mount each other before playing with the box. Such situations lead to squabbles in most other species. But bonobos are quite tolerant, perhaps because they use sex to divert attention and to defuse tension.<ref name="De_Waal_1995" /><ref>{{cite book |last=de Waal |first=Frans B. M. |title=The Ape and the Sushi Master: Cultural Reflections by a Primatologist |title-link=The Ape and the Sushi Master |publisher=[[Basic Books]] |year=2001 |isbn=978-84-493-1325-7 |chapter=Bonobos and Fig Leaves |author-link=Frans de Waal |name-list-style=vanc}}</ref>

Bonobo sex often occurs in aggressive contexts totally unrelated to food. A jealous male might chase another away from a female, after which the two males reunite and engage in [[scrotum|scrotal]] rubbing. Or after a female hits a juvenile, the latter's mother may lunge at the aggressor, an action that is immediately followed by genital rubbing between the two adults.<ref name="De_Waal_1995" />

===== Chimpanzees =====
Compared to bonobos, less research has been conducted on same-sex sexual behaviors in chimpanzees (''Pan troglodytes''). In contrast to bonobos, same-sex sexual behaviors are less common in Kibale chimpanzees (''Pan troglodytes schweinfurthii'') and primarily occur between adult males.<ref>{{Cite journal |last1=Sandel |first1=Aaron A. |last2=Reddy |first2=Rachna B. |date=2021-02-02 |title=Sociosexual behaviour in wild chimpanzees occurs in variable contexts and is frequent between same-sex partners |url=https://brill.com/view/journals/beh/158/3-4/article-p249_3.xml |journal=Behaviour |volume=158 |issue=3–4 |pages=249–276 |doi=10.1163/1568539X-bja10062 |s2cid=234056789 |issn=0005-7959|url-access=subscription }}</ref> While less frequent than in female bonobos, same-sex sexual behaviors between male chimpanzees occur regularly and in a variety of contexts. Female chimpanzees are much less likely to engage in same-sex sexual behaviors than males.

===== Gibbons =====
There is one published study of same-sex sexual behavior in white-handed gibbons (''Hylobates lar''). The authors report on observations of an adult male mounting an adolescent male. In gibbons, same-sex sexual behavior is likely rare.<ref>{{Cite journal |last1=Edwards |first1=Anna-Marie A. R. |last2=Todd |first2=John D. |date=1991-04-01 |title=Homosexual behaviour in wild white-handed gibbons (Hylobates lar) |url=https://doi.org/10.1007/BF02381180 |journal=Primates |language=en |volume=32 |issue=2 |pages=231–236 |doi=10.1007/BF02381180 |s2cid=26662075 |issn=1610-7365|url-access=subscription }}</ref>

=====Gorillas=====
{{See also|Gorilla#Social structure}}Both male and female mountain gorillas (''Gorilla gorilla beringei'') have been observed engaging in same-sex sexual behaviors.<ref>{{Cite web |title=Does homosexual behaviour exist among gorillas? |url=https://www.berggorilla.org/en/gorillas/general/social-life/does-homosexual-behaviour-exist-among-gorillas/ |access-date=2023-10-22 |website=Berggorilla & Regenwald Direkthilfe e.V. |language=en}}</ref> Homosexual behavior among male gorillas has been studied.<ref>{{Cite journal |last=Yamagiwa |first=Juichi |name-list-style=vanc |date=1987-01-01 |title=Intra- and inter-group interactions of an all-male group of virunga mountain gorillas (Gorilla gorilla beringei) |journal=Primates |language=en |volume=28 |issue=1 |pages=1–30 |doi=10.1007/BF02382180 |issn=1610-7365 |s2cid=24667667}}</ref> This behavior occurs more often in all-male bachelor packs in the wild and it is believed to play a role in social bonding. Homosexual behavior among female [[mountain gorilla]]s has also been documented.<ref>{{cite journal |vauthors=Grueter CC, Stoinski TS |date=2016-05-11 |title=Homosexual Behavior in Female Mountain Gorillas: Reflection of Dominance, Affiliation, Reconciliation or Arousal? |journal=PLOS ONE |volume=11 |issue=5 |pages=e0154185 |bibcode=2016PLoSO..1154185G |doi=10.1371/journal.pone.0154185 |pmc=4864209 |pmid=27167861 |doi-access=free}}</ref> Among all-male "bachelor" groups, same-sex sexual interactions are extremely common.<ref>{{Cite journal |last=Yamagiwa |first=Juichi |date=1987-01-01 |title=Intra- and inter-group interactions of an all-male group of virunga mountain gorillas (Gorilla gorilla beringei) |url=https://doi.org/10.1007/BF02382180 |journal=Primates |language=en |volume=28 |issue=1 |pages=1–30 |doi=10.1007/BF02382180 |s2cid=24667667 |issn=1610-7365|url-access=subscription }}</ref> Female mountain gorillas engage in same-sex sexual behaviors frequently as well, and coincided in prevalence in accordance with intersexual copulations as well. As opposed to conferring social status, same-sex sexual behaviors are likely reflective of elevated arousal in female mountain gorillas.<ref>{{Cite web |last=Australia |first=University of Western |title=Homosexual activity documented in female gorillas for the first time |url=https://phys.org/news/2016-05-homosexual-documented-female-gorillas.html |access-date=2023-10-22 |website=phys.org |language=en}}</ref> Same-sex sexual behaviors are natural and common among mountain gorillas.

=====Orangutans=====
Homosexual behavior forms part of the natural repertoire of sexual or sociosexual behavior of [[orangutan]]s. Male homosexual behavior occurs both in the wild and in captivity, and it occurs in both adolescent and mature individuals. Homosexual behavior in orangutans is not an artifact of captivity or contact with humans.<ref name="Fox-2001">{{cite journal |vauthors=Fox EA |date=November 2001 |title=Homosexual behavior in wild Sumatran orangutans (Pongo pygmaeus abelii) |journal=[[American Journal of Primatology]] |volume=55 |issue=3 |pages=177–81 |doi=10.1002/ajp.1051 |pmid=11746281 |s2cid=21561581}}</ref>

Sociosexual behaviors among orangutans (''Pongo spp.'') are extremely common and invoke a variety of evolutionary strategies.<ref>{{Cite journal |last1=Kunz |first1=Julia A. |last2=Duvot |first2=Guilhem J. |last3=Willems |first3=Erik P. |last4=Stickelberger |first4=Julia |last5=Spillmann |first5=Brigitte |last6=Utami Atmoko |first6=Sri Suci |last7=van Noordwijk |first7=Maria A. |last8=van Schaik |first8=Carel P. |date=December 2021 |title=The context of sexual coercion in orang-utans: when do male and female mating interests collide? |journal=Animal Behaviour |volume=182 |pages=67–90 |doi=10.1016/j.anbehav.2021.09.012 |issn=0003-3472|doi-access=free }}</ref><ref>{{Cite journal |last1=O'Connell |first1=Caitlin A. |last2=Susanto |first2=Tri Wahyu |last3=Knott |first3=Cheryl D. |date=November 2020 |title=Sociosexual behavioral patterns involving nulliparous female orangutans ( Pongo sp.) reflect unique challenges during the adolescent period |url=https://onlinelibrary.wiley.com/doi/10.1002/ajp.23058 |journal=American Journal of Primatology |language=en |volume=82 |issue=11 |pages=e23058 |doi=10.1002/ajp.23058 |pmid=31583721 |s2cid=203659435 |issn=0275-2565|url-access=subscription }}</ref> However, only one study of same-sex sexual behavior has been published.<ref>{{Cite journal |last=Fox |first=Elizabeth A. |date=2001 |title=Homosexual behavior in wild Sumatran orangutans (Pongo pygmaeus abelii) |url=http://dx.doi.org/10.1002/ajp.1051 |journal=American Journal of Primatology |volume=55 |issue=3 |pages=177–181 |doi=10.1002/ajp.1051 |pmid=11746281 |s2cid=21561581 |issn=0275-2565|url-access=subscription }}</ref> In Sumatran orangutans (''Pongo abelii''), same-sex sexual behavior has been documented among two dyads of unflanged adolescent males. Oral contact with genitals and behavior similar to male-female forced copulation between sexually mature sub-adult males were observed.

=====Monkeys=====
Among monkeys{{clarify|date=June 2012}}, [[Lionel Tiger]] and [[Robin Fox]] conducted a study on how [[Depo-Provera]] [[contraceptive]]s lead to decreased male attraction to females.<ref>{{cite book|url=https://books.google.com/books?id=LiyrEhQPmRsC&pg=PA66| first = Lionel | last = Tiger | name-list-style = vanc |pages=66ff|year=1992|title=The Pursuit of Pleasure|publisher=Transaction Publishers|isbn=978-0-7658-0696-3}}</ref>

======Japanese macaques======
{{further|Japanese macaque#Behavior}}
With the [[Japanese macaque]], also known as the "snow [[monkey]]", [[Homosexuality|same-sex relations]] are frequent, though rates vary between troops. Females will form "[[wikt:consort|consort]]ships" characterized by affectionate social and sexual activities. In some troops up to one quarter of the females form such bonds, which vary in duration from a few days to a few weeks. Often, strong and lasting friendships result from such pairings. Males also have same-sex relations, typically with multiple partners of the same age. Affectionate and playful activities are associated with such relations.<ref name=Bagemihl/>{{rp|302–305}}

====Sheep====
{{main|Homosexual behavior in sheep}}
''[[Ovis aries]],'' the common domesticated sheep, has attracted much attention due to the fact that around 8–10% of rams have an exclusive homosexual orientation.{{refn|<ref name="Poiani2010"/><ref name="The Volume of a Sexually Dimorphic"/><ref>{{cite journal | vauthors = Roselli CE, Stormshak F | title = The neurobiology of sexual partner preferences in rams | journal = Hormones and Behavior | volume = 55 | issue = 5 | pages = 611–20 | date = May 2009 | pmid = 19446078 | pmc = 2684522 | doi = 10.1016/j.yhbeh.2009.03.013 }}</ref><ref name="ncbi.nlm.nih.gov">{{cite journal | vauthors = Roselli CE, Stormshak F | title = Prenatal programming of sexual partner preference: the ram model | journal = Journal of Neuroendocrinology | volume = 21 | issue = 4 | pages = 359–64 | date = March 2009 | pmid = 19207819 | pmc = 2668810 | doi = 10.1111/j.1365-2826.2009.01828.x }}</ref><ref>{{cite journal | vauthors = Perkins A, Fitzgerald JA, Price EO | title = Luteinizing hormone and testosterone response of sexually active and inactive rams | journal = Journal of Animal Science | volume = 70 | issue = 7 | pages = 2086–93 | date = July 1992 | pmid = 1644682 | doi = 10.2527/1992.7072086x | url = https://www.animalsciencepublications.org/publications/jas/articles/70/7/2086 | access-date = 2015-07-07 | archive-url = https://web.archive.org/web/20170630082018/https://www.animalsciencepublications.org/publications/jas/articles/70/7/2086 | archive-date = 2017-06-30 | url-status=dead | url-access = subscription }}</ref><ref name="Rosellietal2004">{{cite journal | vauthors = Roselli CE, Larkin K, Schrunk JM, Stormshak F | title = Sexual partner preference, hypothalamic morphology and aromatase in rams | journal = Physiology & Behavior | volume = 83 | issue = 2 | pages = 233–45 | date = November 2004 | pmid = 15488542 | doi = 10.1016/j.physbeh.2004.08.017 | s2cid = 156571 }}</ref>}} Such rams prefer to court and mount other rams only, even in the presence of estrous ewes.<ref name="Poiani2010"/> Moreover, around 18–22% of rams are bisexual.<ref name="ncbi.nlm.nih.gov"/>

Several observations indicate that male–male sexual preference in rams is sexually motivated. Rams routinely perform the same courtship behaviors (including foreleg kicks, nudges, vocalizations, anogenital sniffs and [[flehmen response|flehmen]]) prior to mounting other males as observed when other rams court and mount estrous females. Furthermore, pelvic thrusting and ejaculation often accompany same-sex mounts by rams.<ref name="Rosellietal2004"/>

====Spotted hyenas====
{{see also|Animal sexual behaviour#Spotted hyena|Spotted hyena#Reproduction and development}}

[[File:Spotted hyena2.jpg|right|thumb|The [[spotted hyena]] is a moderately large, terrestrial carnivore native to [[Africa]].]]
The family structure of the spotted hyena is [[matriarchal]], and dominance relationships with strong sexual elements are routinely observed between related females. Due largely to [[Clitoris#Spotted hyenas|the female spotted hyena's unique urogenital system]], which looks more like a penis rather than a vagina, early naturalists thought hyenas were [[hermaphrodite|hermaphroditic]] males who commonly practiced [[homosexuality]].<ref name="Like mother, like cubs">{{cite web | title= Like mother, like cubs: Hyena alpha moms jumpstart cubs with hormonal jolt | publisher=[[Michigan State University]] | year=2006 | url=http://hyenas.zoology.msu.edu/crocuta/hyena_research_overview.html | access-date = 2007-09-11 |archive-url = https://web.archive.org/web/20070629155747/http://hyenas.zoology.msu.edu/crocuta/hyena_research_overview.html <!-- Bot retrieved archive --> |archive-date = 2007-06-29}}</ref>{{failed verification|date=May 2015}} Early writings such as [[Ovid]]'s ''[[Metamorphoses]]'' and the ''[[Physiologus]]'' suggested that the hyena continually changed its sex and nature from male to female and back again. In ''[[Paedagogus]]'', Clement of Alexandria noted that the [[hyena]] (along with the [[hare]]) was "quite obsessed with sexual intercourse". Many Europeans associated the hyena with sexual deformity, prostitution, deviant sexual behavior, and even witchcraft.

The reality behind the confusing reports is the sexually aggressive behavior between the females, including mounting between females. Research has shown that "in contrast to most other female mammals, female ''[[Crocuta]]'' are male-like in appearance, larger than males, and substantially more aggressive,"<ref name="Research: Spotted Hyena - Introduction">{{cite web | last =Holekamp | first =Kay E. | name-list-style = vanc | title=Research: Spotted Hyena - Introduction and Overview | publisher=[[Michigan State University]], Department of [[Zoology]] |year=2003 |url=http://hyenas.zoology.msu.edu/crocuta/hyena_research_overview.html |access-date = 2007-09-11 |archive-url = https://web.archive.org/web/20070629155747/http://hyenas.zoology.msu.edu/crocuta/hyena_research_overview.html <!-- Bot retrieved archive --> |archive-date = 2007-06-29}}</ref> and they have "been masculinized without being defeminized".<ref name="Like mother, like cubs"/>{{failed verification|date=May 2015}}

Study of this unique [[genitalia]] and aggressive behavior in the female hyena has led to the understanding that more aggressive females are better able to compete for resources, including food and mating partners.<ref name="Like mother, like cubs"/><ref name="Top Dogs: Steroid hormones">{{cite web | last =Selim | first =Jocelyn | name-list-style = vanc | title=Top Dogs: Steroid hormones give hyenas a head start. | work=[[Discover Magazine]] | date=2006-04-28 | url=http://discovermagazine.com/2006/apr/hormone-hyenas | access-date = 2007-09-11}}</ref> Research has shown that "elevated levels of [[testosterone]] [[Uterus|in utero]]"<ref name="Sexual Dimorphism of Perineal"/> contribute to extra aggressiveness; both males and females mount members of both the same and opposite sex,<ref name="Sexual Dimorphism of Perineal">{{cite journal | vauthors = Forger NG, Frank LG, Breedlove SM, Glickman SE | title = Sexual dimorphism of perineal muscles and motoneurons in spotted hyenas | journal = The Journal of Comparative Neurology | volume = 375 | issue = 2 | pages = 333–43 | date = November 1996 | pmid = 8915834 | doi = 10.1002/(SICI)1096-9861(19961111)375:2<333::AID-CNE11>3.0.CO;2-W | doi-access = free }}</ref><ref name="Wilson, Sexing the Hyena">{{cite journal |author=Anna Wilson |title=Sexing the Hyena: Intraspecies Readings of the Female Phallus |journal=Signs |volume=28 |issue=3 |pages=755–790 |date=Spring 2003 | publisher=[[University of Chicago Press]] |doi=10.1086/345320|s2cid=146640802 }}</ref> who in turn are possibly acting more [[submissive]] because of lower levels of testosterone in utero.<ref name="Research: Spotted Hyena - Introduction" />

===Reptiles===
====Lizards====
{{further|Animal sexual behaviour#Lizards}}
Several species of [[Teiidae|whiptail lizard]] (especially in the genus ''[[Aspidoscelis]]'') consist only of females that have the ability to reproduce through [[parthenogenesis]].<ref>{{cite journal |last1=Cole |first1=Charles J.| last2 = Townsend | first2 = Carol R.| name-list-style = vanc |date=9 May 2005|title=Parthenogenetic lizards as vertebrate systems |journal=Journal of Experimental Zoology|volume=256 |issue=S4|pages=174–176 |doi=10.1002/jez.1402560436|pmid=1974787}}</ref> Females engage in sexual behavior to stimulate [[ovulation]], with their behavior following their hormonal cycles; during low levels of estrogen, these (female) lizards engage in "masculine" sexual roles. Those animals with currently high estrogen levels assume "feminine" sexual roles. Some parthenogenetic lizards that perform the courtship ritual have greater fertility than those kept in isolation due to an increase in hormones triggered by the sexual behaviors. So, even though [[asexual reproduction|asexual]] whiptail lizards populations lack males, [[sexual stimuli]] still increase reproductive success. From an [[evolutionary]] standpoint, these females are passing their full genetic code to all of their offspring (rather than the 50% of genes that would be passed in sexual reproduction). Certain species of [[gecko]] also reproduce by parthenogenesis.<ref>{{cite web|url=https://www.sciencedaily.com/releases/2005/06/050608053415.htm|title=Geckos: It's Not Always About Sex|last=Anon|date=9 June 2005|work=Science Daily|publisher=Lewis & Clark College |access-date=2008-12-14}}</ref>

Some species of sexually reproducing [[gecko]]s have also been found to display homosexual behavior, e.g. the day geckos [[Gold dust day gecko|''Phelsuma laticauda'']] and [[Blue-tailed day gecko|''Phelsuma cepediana'']].<ref>{{Cite journal|vauthors=Budzinski RM|date=1997|title=Homosexuelles Verhalten bei Geckos der Gattung Phelsuma.|url=http://www.sauria.de|journal=Sauria|volume=19|issue=3|pages=33–34|access-date=2020-07-25|archive-url=https://web.archive.org/web/20200607100011/https://sauria.de/|archive-date=2020-06-07|url-status=dead}}</ref>

====Tortoises====
[[Jonathan (tortoise)|Jonathan]], the world's oldest [[tortoise]] (an [[Aldabra giant tortoise]]), had been mating with another tortoise named Frederica since 1991. In 2017, it was discovered that Frederica was actually probably male all along, and was renamed Frederic.<ref name="thetimessthelenatortoise">{{cite news|last1=Binyon|first1=Michael| name-list-style = vanc |title=St Helena tortoise has a gay old time|url=https://www.thetimes.com/article/st-helena-tortoise-has-a-gay-old-time-6lcvnff7p|access-date=October 20, 2017|work=[[The Times]]|date=October 19, 2017}}</ref>

===Insects and arachnids===
There is evidence of same-sex sexual behavior in at least 110 species of insects and arachnids.<ref name="scharf2013">{{cite journal | vauthors = Scharf I, Martin OY | year = 2013 | title = Same-sex sexual behavior in insects and arachnids: prevalence, causes, and consequences | journal = Behavioral Ecology and Sociobiology | volume = 67 | issue = 11 | pages = 1719–1730 | doi=10.1007/s00265-013-1610-x| bibcode = 2013BEcoS..67.1719S | s2cid = 10899013 }}</ref> Scharf et al. says: "Males are more frequently involved in same-sex sexual (SSS)  behavior in the laboratory than in the field, and isolation, high density, and exposure to female pheromones increase its prevalence. SSS behavior is often shorter than the equivalent heterosexual behavior. Most cases can be explained via mistaken identification by the active (courting/mounting) male. Passive males often resist courting/mating attempts".<ref name="scharf2013" />

Scharf et al. continues: "SSS behavior has been reported in most insect orders, and Bagemihl (1999) provides a list of ~100 species of insects demonstrating such behavior. Yet, this list lacks detailed descriptions, and a more comprehensive summary of its prevalence in invertebrates, as well as ethology, causes, implications, and evolution of this behavior, remains lacking".<ref name="scharf2013" />

====Dragonflies====
[[File:Head of dragonfly 2.jpg|thumb|The head of darner dragonfly (''Basiaeschna janata'')]]

Male homosexuality has been inferred in several species of [[dragonflies]] (the [[Order (biology)|order]] [[Odonata]]). The [[cloacal]] pinchers of male [[damselflies]] and dragonflies inflict characteristic head damage to females during sex. A survey of 11 species of damsel and dragonflies<ref>{{cite journal | vauthors = Dunkle SW | year = 1991 | title = Head damage from mating attempts in dragonflies (Odonata:Anisoptera) | url =https://www.biodiversitylibrary.org/page/16252041 | journal = Entomological News | volume = 102 | issue =1 | pages = 37–41 }}</ref><ref>{{cite journal | vauthors = Utzeri C, Belfiore C | year = 1990 | title = Anomalous tandems in Odonata | journal = Fragmenta Entomologica | volume = 22 | issue = 2| pages = 271–288 }}</ref> has revealed such mating damages in 20 to 80% of the males too, indicating a fairly high occurrence of sexual coupling between males.

====Fruit flies====
Male ''[[Drosophila melanogaster]]'' flies bearing two copies of a mutant allele in the [[Fruitless (gene)|fruitless]] gene court and attempt to mate exclusively with other males.<ref name="Gailey1">{{cite journal | vauthors = Gailey DA, Hall JC | title = Behavior and cytogenetics of fruitless in Drosophila melanogaster: different courtship defects caused by separate, closely linked lesions | journal = Genetics | volume = 121 | issue = 4 | pages = 773–85 | date = April 1989 | doi = 10.1093/genetics/121.4.773 | pmid = 2542123 | pmc = 1203660 | url = http://www.genetics.org/cgi/content/abstract/121/4/773 }}</ref> The genetic basis of animal homosexuality has been studied in the fly ''D. melanogaster''.<ref name="yamamoto3">{{cite journal | vauthors = Yamamoto D, Nakano Y | title = Sexual behavior mutants revisited: molecular and cellular basis of Drosophila mating | journal = Cellular and Molecular Life Sciences | volume = 56 | issue = 7–8 | pages = 634–46 | date = November 1999 | pmid = 11212311 | doi = 10.1007/s000180050458 | s2cid = 22055533 | pmc = 11146922 }}</ref> Here, multiple genes have been identified that can cause homosexual courtship and mating.<ref name=Yamamoto>{{cite journal | vauthors = Yamamoto D, Ito H, Fujitani K | title = Genetic dissection of sexual orientation: behavioral, cellular, and molecular approaches in Drosophila melanogaster | journal = Neuroscience Research | volume = 26 | issue = 2 | pages = 95–107 | date = October 1996 | pmid = 8953572 | doi = 10.1016/S0168-0102(96)01087-5 | s2cid = 36582275 }}</ref> These genes are thought to control behavior through [[pheromone]]s as well as altering the structure of the animal's brains.<ref name="ferveur">{{cite journal | vauthors = Ferveur JF, Savarit F, O'Kane CJ, Sureau G, Greenspan RJ, Jallon JM | title = Genetic feminization of pheromones and its behavioral consequences in Drosophila males | journal = Science | volume = 276 | issue = 5318 | pages = 1555–8 | date = June 1997 | pmid = 9171057 | doi = 10.1126/science.276.5318.1555 }}</ref><ref name="yamamoto2">{{cite journal | vauthors = Yamamoto D, Fujitani K, Usui K, Ito H, Nakano Y | title = From behavior to development: genes for sexual behavior define the neuronal sexual switch in Drosophila | journal = Mechanisms of Development | volume = 73 | issue = 2 | pages = 135–46 | date = May 1998 | pmid = 9622612 | doi = 10.1016/S0925-4773(98)00042-2 | s2cid = 14531382 }}</ref> These studies have also investigated the influence of environment on the likelihood of flies displaying homosexual behavior.<ref name="zhang">{{cite journal | vauthors = Zhang SD, Odenwald WF | title = Misexpression of the white (w) gene triggers male-male courtship in Drosophila | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 92 | issue = 12 | pages = 5525–9 | date = June 1995 | pmid = 7777542 | pmc = 41728 | doi = 10.1073/pnas.92.12.5525 | bibcode = 1995PNAS...92.5525Z | doi-access = free }}</ref><ref name="svetec">{{cite journal | vauthors = Svetec N, Ferveur JF | title = Social experience and pheromonal perception can change male-male interactions in Drosophila melanogaster | journal = The Journal of Experimental Biology | volume = 208 | issue = Pt 5 | pages = 891–8 | date = March 2005 | pmid = 15755887 | doi = 10.1242/jeb.01454 | doi-access = free | bibcode = 2005JExpB.208..891S }}</ref>

====Bed bugs====
{{Main|Bed bug#Reproduction}}
Male [[Cimex lectularius|bed bug]]s (''Cimex lectularius'') are sexually attracted to any newly fed individual and this results in homosexual mounting. This occurs in heterosexual mounting by the [[traumatic insemination]] in which the male pierces the female abdomen with his needle-like penis. In homosexual mating this risks abdominal injuries as males lack the female counteradaptive [[spermalege]] structure. Males produce alarm [[pheromone]]s to reduce such homosexual mating.