View source for Animal sexual behaviour

{{Short description|Sexual behavior of non-human animals}}
{{About|the sexual behavior of nonhuman animals|human sexual behavior|Human sexual activity|and|Human sexuality|other uses|Animal sex (disambiguation)}}
{{Use dmy dates|date=July 2020}}{{Use British English|date=August 2016}}
[[File:Bonobo sexual behavior 1.jpg|thumb|[[Bonobo|Bonobos]] mating in a zoo]]{{Sexual orientation}}
[[File:KaempfendeHirsche-2-cropped.jpg|thumb|[[Stags]] fighting while competing for females—a common sexual behavior]]
[[File:Anatomy of turkey head.jpg|thumb|Anatomical structures on the head and throat of a domestic [[Turkey (bird)|turkey]]. 1. Caruncles 2. Snood 3. Wattle (dewlap) 4. Major caruncle 5. Beard. During sexual behavior, these structures enlarge or become brightly colored.]]
'''Animal sexual behaviour''' takes many different forms, including within the same [[species]]. Common [[mating]] or [[Reproduction|reproductively]] motivated systems include [[Monogamous pairing in animals|monogamy]], [[Polygyny in animals|polygyny]], [[Polyandry in nature|polyandry]], [[Animal sexual behaviour#Polygamy|polygamy]] and [[Promiscuity#Other animals|promiscuity]]. Other sexual behaviour may be reproductively motivated (e.g. [[Sexual coercion among animals|sex apparently due to duress or coercion]] and [[situational sexual behaviour]]) or [[Non-reproductive sexual behavior in animals|non-reproductively motivated]] (e.g. [[Homosexual behavior in animals|homosexual sexual behaviour]], [[bisexuality|bisexual]] sexual behaviour, [[cross-species sex]], [[Paraphilia|sexual arousal from objects or places]], [[Necrophilia in animals|sex with dead animals]], etc.).

When animal sexual behaviour is reproductively motivated, it is often termed ''mating'' or ''[[Copulation (zoology)|copulation]]''; for most non-human [[mammal]]s, mating and copulation occur at [[Estrous cycle|oestrus]] (the most fertile period in the mammalian female's reproductive cycle), which increases the chances of [[internal fertilization|successful impregnation]].<ref name="Kent">{{Cite book |author= Kent, Michael |title= Advanced biology |isbn= 978-0-19-914195-1 |publisher= [[Oxford University Press]] |year= 2000 |pages= 250–253 |url= https://books.google.com/books?id=8aw4ZWLABQkC&pg=PA250}}</ref><ref>{{cite book |title= General Studies Manual |publisher= [[Pearson Education|Pearson Education India]]|year= 2009 |page=17 |isbn= 9788131721339 |url= https://books.google.com/books?id=oAo1X2eagywC&pg=RA1-PR17 |last1=Thorpe |first1=Showick |last2=Thorpe |first2=Edgar}}</ref> Some animal sexual behaviour involves [[Competition (biology)|competition]], sometimes fighting, between multiple males. Females often select males for mating only if they appear strong and able to protect themselves. The male that wins a fight may also have the chance to mate with a larger number of females and will therefore pass on his genes to their offspring.<ref>{{cite journal |author1=Wickler, Wolfgang |author2=Lorenz |author3=Konrad |author4=Kacher, Hermann |title= The sexual code : the social behaviour of animals and men |year= 1974}}</ref>

Historically, it was believed that only humans and a small number of other species performed sexual acts other than for reproduction, and that animals' sexuality was instinctive and a simple "[[stimulus-response]]" behaviour. However, in addition to homosexual behaviours, a range of species [[Non-reproductive sexual behavior in animals#Autoeroticism or masturbation|masturbate]] and may [[Tool use by animals|use objects as tools]] to help them do so. Sexual behaviour may be tied more strongly to the establishment and maintenance of complex social bonds across a population which support its success in non-reproductive ways. Both reproductive and non-reproductive behaviours can be related to expressions of dominance over another animal or survival within a stressful situation (such as sex due to duress or coercion).

==Mating systems==
[[File:Greater Sage-Grouse at Lek (6948123054).jpg|thumb|[[Greater sage-grouse]] at a [[Lek mating|lek]], with multiple males displaying for the less conspicuous females]]
In [[sociobiology]] and [[behavioural ecology]], the term [[Mating systems#In animals|"mating system"]] is used to describe the ways in which animal societies are structured in relation to sexual behaviour. The mating system specifies which males mate with which females, and under what circumstances. There are four basic systems:

{| class="wikitable"
|-
! colspan="3" style="text-align:center; width:400px;"| The four basic mating systems<ref name="Moyle&Cech">Moyle PB and Cech JJ (2004) ''Fishes, An Introduction to Ichthyology.'' 5th Ed, Benjamin Cummings. {{ISBN|978-0-13-100847-2}}</ref>{{Rp|160–161}}<ref name="Berglund1997">Berglund A (1997) [https://books.google.com/books?id=cF2Uw8HPA60C&pg=PA237 "Mating systems and sex allocation"] Pages 237–265 in JJ Godon, ed. ''Behavioural ecology of teleost fishes''. Oxford University Press. {{ISBN|0-19-850503-5}}.</ref>
|-
!
! Single female
! Multiple females
|-
! Single male
| style="text-align:center;"| [[Monogamous pairing in animals|Monogamy]]
| style="text-align:center;"| [[#Polygyny|Polygyny]]
|-
! Multiple males
| style="text-align:center;"| [[#Polyandry|Polyandry]]
| style="text-align:center;"| [[Polygynandry]]
|}

===Monogamy===
{{Main|Monogamous pairing in animals}}
{{See also|Evolution of monogamy}}

[[Monogamous pairing in animals|Monogamy]] occurs when one male and one female mate exclusively with each other. A monogamous mating system is one in which individuals form [[Pair-bonding|long-lasting pairs]] and cooperate in raising offspring. These pairs may last for a lifetime, such as in [[pigeons]],<ref name="britannica">{{cite encyclopedia |url= https://www.britannica.com/EBchecked/topic/460131/pigeon |title= Pigeon |access-date= 26 August 2014 |encyclopedia= Encyclopædia Britannica }}</ref> or it may occasionally change from one mating season to another, such as in [[emperor penguin]]s.<ref name="NSF">{{cite web |url= https://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=126932 |title= Animal Attraction: The Many Forms of Monogamy in the Animal Kingdom |access-date= 26 August 2014 |author= Lily Whiteman |date= 13 February 2013 |work= National Science Foundation |archive-date= 25 July 2014 |archive-url= https://web.archive.org/web/20140725070543/http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=126932 |url-status= live }}</ref> In contrast with [[tournament species]], these pair-bonding species have lower levels of male aggression, competition and little [[sexual dimorphism]]. [[Zoologists]] and [[biologists]] now have evidence that monogamous pairs of animals are not always sexually exclusive. Many animals that form pairs to mate and raise offspring regularly engage in sexual activities with [[Extra-pair copulation|extra-pair partners]].<ref>{{Cite journal | last1 = Ågren | first1 = G. | last2 = Zhou | first2 = Q. | last3 = Zhong | first3 = W. | title = Ecology and social behaviour of Mongolian gerbils, ''Meriones unguiculatus'', at Xilinhot, Inner Mongolia, China | doi = 10.1016/0003-3472(89)90002-X | journal = Animal Behaviour | volume = 37 | pages = 11–27 | year = 1989 | s2cid = 53152632 }}</ref><ref name="Birkhead, Møller, 1995"/><ref name="Reichard, 2002"/><ref>{{Cite journal | last1 = Westneat | first1 = D. F. | last2 = Stewart | first2 = I. R. K. | doi = 10.1146/annurev.ecolsys.34.011802.132439 | title = Extra-Pair Paternity in Birds: Causes, Correlates, and Conflict | journal = Annual Review of Ecology, Evolution, and Systematics | volume = 34 | pages = 365–396 | year = 2003 }}</ref> This includes previous examples, such as [[swan]]s. Sometimes, these [[Extra-pair copulation|extra-pair sexual activities]] lead to offspring. Genetic tests frequently show that some of the offspring raised by a monogamous pair come from the female mating with an extra-pair male partner.<ref name="Birkhead, Møller, 1995">{{cite journal |author= Birkhead, T.R. |author2=Møller, A.P. |year= 1995 |title= Extra-pair copulations and extra-pair paternity in birds |journal= Animal Behaviour |volume= 49 |issue= 3 |pages= 843–848 |doi= 10.1016/0003-3472(95)80217-7 |s2cid=53156057 }}</ref><ref name="Birkhead, Møller, 1996">Birkhead, T.R. & Møller, A.P. (1996) "Monogamy and sperm competition in birds". In J. M. Black (Ed.), ''Partnerships in Birds: The Study of Monogamy'', [https://books.google.com/books?id=tlHVc42WnOsC&pg=PA323 pp. 323–343], Oxford: Oxford University Press {{ISBN|0-19-854860-5}}.</ref><ref name="Owens, Hartley, 1998">{{Cite journal | last1 = Owens | first1 = I. P. F. | last2 = Hartley | first2 = I. R. | doi = 10.1098/rspb.1998.0308 | title = Sexual dimorphism in birds: Why are there so many different forms of dimorphism? | journal = Proceedings of the Royal Society B: Biological Sciences | volume = 265 | issue = 1394 | pages = 397–407 | year = 1998 | jstor =  50849| pmc = 1688905}}</ref><ref>{{Cite journal | last1 = Solomon | first1 = N. G. | last2 = Keane | first2 = B. | last3 = Knoch | first3 = L. R. | last4 = Hogan | first4 = P. J. | title = Multiple paternity in socially monogamous prairie voles (Microtus ochrogaster) | doi = 10.1139/z04-142 | journal = Canadian Journal of Zoology | volume = 82 | issue = 10 | pages = 1667–1671 | year = 2004 | bibcode = 2004CaJZ...82.1667S }}</ref> These discoveries have led biologists to adopt new ways of talking about monogamy. According to Ulrich Reichard (2003):

{{blockquote|Social monogamy refers to a male and female's social living arrangement (e.g., shared use of a territory, behaviour indicative of a social pair, and/or proximity between a male and female) without inferring any sexual interactions or reproductive patterns. In humans, social monogamy takes the form of monogamous marriage. Sexual monogamy is defined as an exclusive sexual relationship between a female and a male based on observations of sexual interactions. Finally, the term genetic monogamy is used when DNA analyses can confirm that a female-male pair reproduce exclusively with each other. A combination of terms indicates examples where levels of relationships coincide, e.g., sociosexual and sociogenetic monogamy describe corresponding social and sexual, and social and genetic monogamous relationships, respectively.<ref>Reichard, U.H. (2003). Monogamy: Past and present. In U.H. Reichard and C. Boesch (Eds.), Monogamy: Mating strategies and partnerships in birds, humans, and other mammals, pp. 3–25, Cambridge: Cambridge University Press, {{ISBN|0521819733}}.</ref>}}

Whatever makes a pair of animals socially monogamous does not necessarily make them sexually or genetically monogamous. Social monogamy, sexual monogamy, and genetic monogamy can occur in different combinations.

Social monogamy is relatively rare in the animal kingdom. The actual incidence of social monogamy varies greatly across different branches of the evolutionary tree. Over 90% of avian species are socially monogamous.<ref name="Reichard, 2002">{{cite journal|last=Reichard |first=U.H. |year=2002 |title=Monogamy – a variable relationship |journal=Max Planck Research |volume=3 |pages=62–67 |url=http://www.mpg.de/1028786/W001_Biology-Medicine_062_067.pdf |access-date=24 April 2013 |url-status=dead |archive-url=https://web.archive.org/web/20110514183645/http://www.mpg.de/1028786/W001_Biology-Medicine_062_067.pdf |archive-date=14 May 2011 }}</ref><ref name="Barash, Lipton, 2001">Barash, D.P. & Lipton, J.E. (2001). The Myth of Monogamy. New York, NY: W.H. Freeman and Company, {{ISBN|0805071369}}.</ref> This stands in contrast to mammals. Only 3% of mammalian species are socially monogamous, although up to 15% of primate species are.<ref name="Reichard, 2002" /><ref name="Barash, Lipton, 2001" /> Social monogamy has also been observed in [[reptile]]s, fish, and [[insects]].

Sexual monogamy is also rare among animals. Many socially monogamous species engage in [[extra-pair copulation]]s, making them sexually non-monogamous. For example, while over 90% of birds are socially monogamous, "on average, 30% or more of the baby birds in any nest [are] sired by someone other than the resident male."<ref name="NY Times Mating">{{cite news |url= https://query.nytimes.com/gst/fullpage.html?res=9C0CEFDC143FF932A1575BC0A966958260 |work= The New York Times |title= Mating for Life? It's Not for the Birds of the Bees |first= Natalie |last= Angier |date= 21 August 1990 |access-date= 14 February 2017 |archive-date= 5 November 2007 |archive-url= https://web.archive.org/web/20071105034546/http://query.nytimes.com/gst/fullpage.html?res=9C0CEFDC143FF932A1575BC0A966958260 |url-status= live }}</ref> [[Patricia Adair Gowaty]] has estimated that, out of 180 different species of socially monogamous songbirds, only 10% are sexually monogamous.<ref name="Gowaty, Morell, 1998">{{Cite journal 
| last1 = Morell | first1 = V. 
| title = Evolution of Sex: A New Look at Monogamy
| doi = 10.1126/science.281.5385.1982 
| journal = Science 
| volume = 281 
| issue = 5385 
| pages = 1982–1983 
| year = 1998 
| pmid =  9767050
| s2cid = 31391458 
}}</ref>

The incidence of genetic monogamy, determined by DNA fingerprinting, varies widely across species. For a few rare species, the incidence of genetic monogamy is 100%, with all offspring genetically related to the socially monogamous pair. But genetic monogamy is strikingly low in other species. Barash and Lipton note:

{{blockquote|The highest known frequency of extra-pair copulations are found among the [[fairy-wren]]s, lovely tropical creatures technically known as ''[[Malurus splendens]]'' and ''[[Malurus cyaneus]]''. More than 65% of all fairy-wren chicks are fathered by males outside the supposed breeding group.<ref name="Barash, Lipton, 2001" />{{sup|p. 12}}}}

Such low levels of genetic monogamy have surprised biologists and zoologists, forcing them to rethink the role of social monogamy in evolution. They can no longer assume social monogamy determines how genes are distributed in a species. The lower the rates of genetic monogamy among socially monogamous pairs, the less of a role social monogamy plays in determining how genes are distributed among offspring.

===Polygamy===
{{See also|Promiscuity#Other animals}}

The term [[polygamy]] is an umbrella term used to refer generally to non-monogamous matings. As such, polygamous relationships can be polygynous, polyandrous or polygynandrous. In a small number of species, individuals can display either polygamous or monogamous behaviour depending on environmental conditions. An example is the social wasp ''[[Apoica flavissima]]''.{{citation needed|date=November 2014}} In some species, polygyny and polyandry is displayed by both sexes in the population. Polygamy in both sexes has been observed in [[Red flour beetle#Polygamy|red flour beetle]] (''Tribolium castaneum''). Polygamy is also seen in many [[Lepidoptera]] species including ''[[Mythimna unipuncta]]'' (true armyworm moth).<ref>{{cite journal | last1 = Mcneil | first1 = Jeremy N | year = 1986 | title = Calling Behavior: Can It Be Used to Identify Migratory Species of Moths | journal = The Florida Entomologist | volume = 69 | issue = 1| pages = 78–84 | doi = 10.2307/3494746 | jstor = 3494746 }}</ref>

A [[tournament species]] is one in which "mating tends to be highly polygamous and involves high levels of male-male aggression and competition."<ref name=twsNovK12>{{cite news |author= Robert Sapolsky |title= Biology and Human Behavior: The Neurological Origins of Individuality, 2nd edition |url= http://www.thegreatcourses.com/tgc/courses/course_detail.aspx?cid=1597 |publisher= The Teaching Company |year= 2005 |access-date= 2010-11-10 |archive-date= 16 February 2014 |archive-url= https://web.archive.org/web/20140216181603/http://www.thegreatcourses.com/tgc/courses/course_detail.aspx?cid=1597 |url-status= live }}</ref> Tournament behaviour often correlates with high levels of [[sexual dimorphism]], examples of species including [[Common chimpanzee|chimpanzees]] and [[baboons]]. Most polygamous species present high levels of tournament behaviour, with a notable exception being [[bonobos]].{{Citation needed|reason=Evidence for bonobo sexual peacefulness is scant|date=April 2018}}

====Polygyny====
{{Main|Polygyny in animals}}

[[Polygyny threshold model|Polygyny]] occurs when one male gets exclusive mating rights with multiple females. In some species, notably those with [[harem (zoology)|harem]]-like structures, only one of a few males in a group of females will mate. Technically, [[Polygyny in nature|polygyny]] in sociobiology and zoology is defined as a system in which a male has a relationship with more than one female, but the females are predominantly bonded to a single male. Should the active male be driven out, killed, or otherwise removed from the group, in a number of species the new male will ensure that breeding resources are not wasted on another male's young.<ref>This section and examples taken from [[Robert Sapolsky]] (1998) ''[[Why Zebras Don't Get Ulcers]]'', W.H. Freeman and Co., {{ISBN|0-7167-3210-6}}, pp. 140–141.</ref> The new male may achieve this in many different ways, including:

* competitive [[infanticide (zoology)|infanticide]]: in [[lion]]s, [[hippopotamuses]], and some [[monkey]]s, the new male will kill the offspring of the previous alpha male to cause their mothers to become receptive to his sexual advances since they are no longer [[lactation|nursing]]. To prevent this, many female primates exhibit ovulation cues among all males, and show situation-dependent receptivity.<ref name="Fürtbauer-2011">{{Cite journal|last1=Fürtbauer|first1=Ines|last2=Heistermann|first2=Michael|last3=Schülke|first3=Oliver|last4=Ostner|first4=Julia|date=2011-08-10|title=Concealed Fertility and Extended Female Sexuality in a Non-Human Primate (''Macaca assamensis'')|journal=PLOS ONE|volume=6|issue=8|pages=e23105|doi=10.1371/journal.pone.0023105|issn=1932-6203|pmc=3154278|pmid=21853074|bibcode=2011PLoSO...623105F|doi-access=free}}</ref>
* [[harassment]] to [[miscarriage]]: amongst wild [[horse]]s and [[baboon]]s, the male will continually attack pregnant females until they miscarry.
* [[Pheromone]]-based [[spontaneous abortion]]
* in some [[rodent]]s such as [[mouse|mice]], a new male with a different scent will cause females who are pregnant to spontaneously fail to implant recently fertilised eggs. This does not require contact; it is mediated by [[scent]] alone. It is known as the [[Bruce effect]].

Von Haartman specifically described the mating behaviour of the [[European pied flycatcher]] as successive polygyny.<ref>{{Cite journal | last1 = Haartman | first1 = L. V. | doi = 10.1163/156853951X00296 | title = Successive Polygamy | journal = Behaviour | volume = 3 | pages = 256–273 | year = 1951}}</ref> Within this system, the males leave their home territory once their primary female lays her first egg. Males then create a second territory, presumably in order to attract a secondary female to breed. Even when they succeed at acquiring a second mate, the males typically return to the first female to exclusively provide for her and her offspring.<ref>{{Cite journal
| last1 = Silverin | first1 = B. 
| title = Effects of long-acting testosterone administration on testes in free living pied flycatchers ''Ficedula hypoleuca'' 
| journal = Endokrinologie 
| volume = 74 
| issue = 2 
| pages = 141–146 
| year = 1979 
| pmid = 583410
}}</ref>

Polygynous mating structures are estimated to occur in up to 90% of mammal species.<ref>{{cite journal |last= Aloise King |first= Edith D. |author2= Banks, Peter B. |author3= Brooks, Robert C. |title= Sexual conflict in mammals: consequences for mating systems and life history |journal= Mammal Review |publication-date= January 2013 |year= 2011 |volume= 43 |issue= 1 |pages= 47–58 |doi= 10.1111/j.1365-2907.2011.00200.x}}</ref> As polygyny is the most common form of polygamy among vertebrates (including humans), it has been studied far more extensively than polyandry or polygynandry.

====Polyandry====
[[File:Hamol u0.gif|thumb|right|The anglerfish ''[[Haplophryne mollis]]'' is polyandrous. This female is trailing the atrophied remains of males she has encountered.]]
{{Main|Polyandry in nature}}

[[Polyandry in nature|Polyandry]] occurs when one female gets exclusive mating rights with multiple males. In some species, such as [[Ophioblennius atlanticus|redlip blennies]], both [[Polygyny in nature|polygyny]] and [[Polyandry in nature|polyandry]] are observed.<ref>{{cite journal |last= Marraro |first= CH |author2= Nursall JR |title= The reproductive periodicity and behaviour of Ophioblennius atlanticus at Barbados |journal= J Zool |year= 1983 |volume= 61 |issue= 2 |pages= 317–325 |doi= 10.1139/z83-042}}</ref>

The males in some deep sea [[anglerfish]]es are much smaller than the females. When they find a female they bite into her skin, releasing an [[enzyme]] that digests the skin of their mouths and her body and fusing the pair down to the blood-vessel level. The male then slowly [[atrophy|atrophies]], losing first his digestive organs, then his brain, heart, and eyes, ending as nothing more than a pair of [[gonads]], which release [[Spermatozoon|sperm]] in response to [[hormones]] in the female's bloodstream indicating [[ovum|egg]] release. This extreme [[sexual dimorphism]] ensures that, when the female is ready to spawn, she has a mate immediately available.<ref name="doran">{{cite journal | author = Theodore W. Pietsch | title = Precocious sexual parasitism in the deep sea ceratioid anglerfish, Cryptopsaras couesi Gill | volume=256 | issue = 5512 | doi=10.1038/256038a0 | journal=Nature | pages=38–40| year = 1975 | bibcode = 1975Natur.256...38P | s2cid = 4226567 }}</ref> A single anglerfish female can "mate" with many males in this manner.

====Polygynandry====
{{Main|Polygynandry}}

[[Polygynandry]] occurs when multiple males mate indiscriminately with multiple females. The numbers of males and females need not be equal, and in vertebrate species studied so far, there are usually fewer males. Two examples of systems in primates are promiscuous mating [[Common chimpanzee|chimpanzees]] and [[bonobo]]s. These species live in social groups consisting of several males and several females. Each female copulates with many males, and vice versa. In bonobos, the amount of promiscuity is particularly striking because bonobos use sex to alleviate social conflict as well as to reproduce.<ref name=":2">{{Cite news|url=http://news.nationalgeographic.com/news/2004/07/0722_040722_gayanimal_2.html|title=Homosexual Activity Among Animals Stirs Debate|date=2004-07-23|access-date=2018-11-18|archive-date=13 November 2015|archive-url=https://web.archive.org/web/20151113071554/http://news.nationalgeographic.com/news/2004/07/0722_040722_gayanimal_2.html|url-status=dead}}</ref> This mutual promiscuity is the approach most commonly used by spawning animals, and is perhaps the "original fish mating system."<ref name="Moyle&Cech" />{{Rp|161}} Common examples are [[forage fish]], such as [[herring]]s, which form huge mating [[Shoaling and schooling|shoals]] in shallow water. The water becomes milky with sperm and the bottom is draped with millions of fertilised eggs.<ref name="Moyle&Cech" />{{Rp|161}}

==Parental investment and reproductive success==
{{Main|Bateman's principle}}
[[File:Mating Great Grey Slug 4111.jpg|thumb|Mating [[Limax maximus|grey slugs]], suspended from a slime thread]]

Female and male sexual behaviour differ in many species. Often, males are more active in initiating mating, and bear the more conspicuous sexual ornamentation like antlers and colourful plumage. This is a result of [[anisogamy]], where [[sperm]] are smaller and much less costly (energetically) to produce than [[egg]]s. This difference in physiological cost means that males are more limited by the number of mates they can secure, while females are limited by the quality of genes of her mates, a phenomenon known as [[Bateman's principle]].<ref>{{Citation | last = Bateman | first = A.J. | title = Intra-sexual selection in Drosophila | journal = Heredity | volume = 2 | pages = 349–368 | year = 1948 | doi = 10.1038/hdy.1948.21 | pmid = 18103134 | issue = Pt. 3| doi-access = free}}</ref> Many females also have extra reproductive burdens in that [[parental care]] often falls mainly, or exclusively, on them. Thus, females are more limited in their potential [[reproductive success]].<ref name=Trivers1972>Trivers, R.L. (1972). Parental investment and sexual selection. In B. Campbell (Ed.), ''Sexual selection and the descent of man'', 1871–1971 (pp.&nbsp;136–179). Chicago, IL: Aldine. {{ISBN|0-435-62157-2}}</ref> In species where males take on more of the reproductive costs, such as [[sea horses]] and [[Jacanidae|jacana]]s, the role is reversed, and the females are larger, more aggressive and more brightly coloured than the males.

In hermaphroditic animals, the costs of parental care can be evenly distributed between the sexes, e.g. [[earthworm]]s. In some species of [[planarian]]s, sexual behaviour takes the form of [[penis fencing]]. In this form of copulation, the individual that first penetrates the other with the penis, forces the other to be female, thus carrying the majority of the cost of reproduction.<ref name="sn">[http://www.sciencenews.org/pages/sn_arc98/2_14_98/fob2.htm Hermaphrodites duel for manhood] {{Webarchive|url=https://web.archive.org/web/20080326155753/http://www.sciencenews.org/pages/sn_arc98/2_14_98/fob2.htm |date=26 March 2008 }}, ''Science News Online''. Accessed 14 March 2009.</ref> Post mating, [[banana slugs]] will some times gnaw off their partners penis as an act of [[sperm competition]] called apophallation.<ref>{{cite book|last1=Miller|first1=Brooke L. W|title=Sexual conflict and partner manipulation in the banana slug, ''Ariolimax dolichophallus''|date=2007|publisher=University of California|location=Santa Cruz|url=http://gradworks.umi.com/32/65/3265732.html|access-date=13 February 2015|archive-date=13 February 2015|archive-url=https://web.archive.org/web/20150213145523/http://gradworks.umi.com/32/65/3265732.html|url-status=live}}</ref> This is costly as they must heal, and spend more energy courting conspecifics that can act as male and female. A hypothesis suggests these slugs may be able to compensate the loss of the male function by directing energy that would have been put towards it to the female function.<ref>{{Cite journal |last1=Backeljau |first1=Thierry |last2=Jordaens |first2=Kurt |last3=Dillen |first3=Lobke |year=2007 |url=https://www.researchgate.net/publication/233602810 |journal=Animal Biology |volume=57 |issue=2 |pages=137–195 |doi=10.1163/157075607780377965 |access-date=2018-11-18|title=Effects of mating, breeding system and parasites on reproduction in hermaphrodites: Pulmonate gastropods (Mollusca)}}</ref> In the [[Limax maximus|grey slug]], the sharing of cost leads to a spectacular display, where the mates suspend themselves high above the ground from a slime thread, ensuring none of them can refrain from taking on the cost of egg-bearer.<ref>{{cite journal|last1=Leonard|first1=J. L.|title=Sexual selection: lessons from hermaphrodite mating systems|journal=Integrative and Comparative Biology|date=5 May 2006|volume=46|issue=4|pages=349–367|doi=10.1093/icb/icj041|pmid=21672747|doi-access=free}}</ref>

==Seasonality==
{{Main|Seasonal breeder}}
[[File:Brain coral spawning.jpg|thumb|right|[[Brain coral]]s typically [[Spawn (biology)|spawning]] in connection with the full moon every August]]

Many animal species have specific mating (or breeding) periods e.g. ([[Seasonal breeder|seasonal breeding]]) so that offspring are born or hatch at an optimal time. In marine species with limited mobility and [[external fertilization|external fertilisation]] like [[coral]]s, [[sea urchin]]s and [[clam]]s, the timing of the common spawning is the only externally visible form of sexual behaviour. In areas with continuously high [[primary production]], some species have a series of breeding seasons throughout the year. This is the case with most primates (who are primarily tropical and subtropical animals). Some animals ([[opportunistic breeders]]) breed dependent upon other conditions in their environment aside from time of year.

===Mammals===
Mating seasons are often associated with changes to herd or group structure, and behavioural changes, including territorialism amongst individuals. These may be annual (e.g. [[Wolves#Reproduction|wolves]]), biannual (e.g. [[canine reproduction|dogs]]) or more frequently (e.g. horses). During these periods, females of most mammalian species are more mentally and physically receptive to sexual advances, a period scientifically described as [[estrous|oestrus]] but commonly described as being "in season" or "in heat". Sexual behaviour may occur outside oestrus,<ref>For example, masturbation, trial mounting, and other behaviours are regularly seen in male animals out of season</ref> and such acts as do occur are not necessarily harmful.<ref name="danish">Denmark, Det Dyreetiske Råd, [https://www.justitsministeriet.dk/sites/default/files/media/Pressemeddelelser/pdf/2006/Udtalelse.pdf Udtalelse om menneskers seksuelle omgang med dyr] {{Webarchive|url=https://web.archive.org/web/20211004053028/https://www.justitsministeriet.dk/sites/default/files/media/Pressemeddelelser/pdf/2006/Udtalelse.pdf |date=4 October 2021 }} (Copenhagen: Justitsministeriet, November 2006), p. 24. "Slimhinden i hundyrets vagina og dyrets adfærd er under indflydelse af dets brunstcyklus. Det betyder, at dyret er fysisk og mentalt mere parat til seksuelle aktiviteter på nogle tidspunkter end på andre. Men dette er ikke ensbetydende med, at den seksuelle aktivitet vil være forbundet med skader, angst og lidelse, hvis den foregår udenfor brunstperioden." (Translation: "The mucous membrane in the female animal's vagina and the animal's behaviour is under influence of its rut cycle. That means that the animal is physically and mentally more ready for sexual activities at some times than at others. But this does not mean that sexual activity will lead to injuries, fear or suffering, if it happens outside the rut period.")</ref>

Some mammals (e.g. domestic cats, rabbits and camelids) are termed [[Induced ovulation (animals)|"induced ovulators"]]. For these species, the female ovulates due to an external stimulus during, or just prior to, mating, rather than ovulating cyclically or spontaneously. Stimuli causing induced ovulation include the sexual behaviour of coitus, sperm and pheromones. Domestic cats have [[penile spines]]. Upon withdrawal of a [[cat's penis]], the spines rake the walls of the female's [[vagina]], which may cause ovulation.<ref name="HayssenTienhoven1993">{{cite book |author1 = Virginia Douglass Hayssen |author2 = Ari Van Tienhoven |title = Asdell's Patterns of Mammalian Reproduction: A Compendium of Species-specific Data |url = https://books.google.com/books?id=yQzSe71g2AcC&q=spines |access-date = 27 September 2013 |year = 1993 |publisher = Cornell University Press |isbn = 978-0-8014-1753-5 }}</ref><ref name="Aronson 1967">{{Cite journal|title=Penile spines of the domestic cat: their endocrine-behavior relations.|last1=Aronson|first1=L. R.|last2=Cooper|first2=M. L.|journal=Anatomical Record|year=1967|volume=157|issue=1|pages=71–78|pmid=6030760|doi=10.1002/ar.1091570111|s2cid=13070242|url=http://www.catcollection.org/files/PenileSpines.pdf|url-status=dead|archive-url=https://web.archive.org/web/20150319031546/http://www.catcollection.org/files/PenileSpines.pdf|archive-date=19 March 2015}}</ref>

===Amphibians===
For many amphibians, an annual breeding cycle applies, typically regulated by ambient temperature, precipitation, availability of surface water and food supply. This breeding season is accentuated in temperate regions, in boreal climate the breeding season is typically concentrated to a few short days in the spring. Some species, such as the ''Rana clamitans'' (green frog), spend from June to August defending their territory. In order to protect these territories, they use five vocalizations.<ref>{{cite journal|last1=Wells|first1=Kentwood D|title=Territoriality in the green frog (Rana clamitans): Vocalizations and agonistic behaviour|journal=Animal Behaviour|date=November 1978|volume=26|issue=4|pages=1051–1054|doi=10.1016/0003-3472(78)90094-5|s2cid=54344542}}</ref>

===Fish===
Like many [[coral reef]] dwellers, the [[clownfish]] spawn around the time of the full moon in the wild. In a group of clownfish, there is a strict dominance hierarchy. The largest and most aggressive female is found at the top. Only two clownfish, a male and a female, in a group reproduce through external fertilisation. Clownfish are sequential hermaphrodites, meaning that they develop into males first, and when they mature, they become females. If the female clownfish is removed from the group, such as by death, one of the largest and most dominant males will become a female. The remaining males will move up a rank in the hierarchy.

==Motivation==
Various [[neurohormone]]s stimulate sexual wanting in animals. In general, studies have suggested that [[dopamine]] is involved in sexual incentive motivation, [[oxytocin]] and [[melanocortin]]s in sexual attraction, and [[noradrenaline]] in sexual arousal.<ref name="georgiadis">{{cite journal | author = Georgiadis, J. R. |author2=Kringelbach, M. L. |author3=Pfaus, J. G. |name-list-style=amp | year = 2012 | title = Sex for fun: a synthesis of human and animal neurobiology | journal = Nature Reviews Urology | volume = 9 | issue = 9 | pages = 486–498 | doi=10.1038/nrurol.2012.151|pmid=22926422 |s2cid=13813765| doi-access = free }}</ref> [[Vasopressin]] is also involved in the sexual behaviour of some animals.<ref name=bear>{{cite book |last=Bear |first= Mark F. |title= Neuroscience, exploring the brain |url= https://archive.org/details/neuroscienceexpl00mark |url-access= registration |year= 2007 |publisher= Lippincott Williams and Wilkins |location= Baltimore, MD |pages= [https://archive.org/details/neuroscienceexpl00mark/page/544 544–545] |isbn= 978-0781760034}}</ref>

===Neurohormones in the mating systems of voles===
The mating system of [[prairie vole]]s is [[Monogamy in animals|monogamous]]; after mating, they form a lifelong bond. In contrast, [[montane vole]]s have a [[Animal sexual behavior#Polygamy|polygamous]] mating system. When montane voles mate, they form no strong attachments, and separate after copulation. Studies<ref>{{cite journal |title=Neuroanatomical distribution of μ-opioid receptor mRNA and binding in monogamous prairie voles (Microtus ochrogaster) and non-monogamous meadow voles (Microtus pennsylvanicus) |journal=Neuroscience |year=2013 |last1=Inoue |first1=K. |last2=Burkett |first2=J. P. |last3=Young |first3=L. J. |volume=244 |pages=122–133 |doi=10.1016/j.neuroscience.2013.03.035 |pmid=23537838 |pmc=4327842 }}</ref> on the brains of these two species have found that it is two neurohormones and their respective receptors that are responsible for these differences in mating strategies. Male prairie voles release vasopressin after copulation with a partner, and an attachment to their partner then develops. Female prairie voles release oxytocin after copulation with a partner, and similarly develop an attachment to their partner.

Neither male nor female montane voles release high quantities of oxytocin or vasopressin when they mate. Even when injected with these neurohormones, their mating system does not change. In contrast, if prairie voles are injected with the neurohormones, they may form a lifelong attachment, even if they have not mated. The differing response to the neurohormones between the two species is due to a difference in the number of oxytocin and vasopressin receptors. Prairie voles have a greater number of oxytocin and vasopressin receptors compared to montane voles, and are therefore more sensitive to those two neurohormones. It's believed that it's the quantity of receptors, rather than the quantity of the hormones, that determines the mating system and bond-formation of either species.{{citation needed|reason=Couldn't it be the other way round?|date=July 2021}}

===Oxytocin and rat sexual behaviour===
Mother rats experience a [[Estrous cycle|postpartum estrus]] which makes them highly motivated to mate. However, they also have a strong motivation to protect their newly born pups. As a consequence, the mother rat solicits males to the nest but simultaneously becomes aggressive towards them to protect her young. If the mother rat is given injections of an oxytocin [[receptor antagonist]], they no longer experience these maternal motivations.<ref name="Kennet">{{cite journal|author1=Kennett, J.E. |author2=McKee, D.T.|year=2012|title=Oxytocin: An emerging regulator of prolactin secretion in the female rat|journal=Journal of Neuroendocrinology|volume=24|issue=3|pages=403–412|doi=10.1111/j.1365-2826.2011.02263.x|pmc=3288386| pmid= 22129099}}</ref>

Prolactin influences social bonding in rats.<ref name="Kennet" />

===Oxytocin and primate sexual behaviour===
Oxytocin plays a similar role in non-human primates as it does in humans.

Grooming, sex, and cuddling frequencies correlate positively with levels of oxytocin. As the level of oxytocin increases so does sexual motivation. While oxytocin plays a major role in parent child relationships, it is also found to play a role in adult sexual relationships. Its secretion affects the nature of the relationship or if there will even be a relationship at all.{{citation needed|date=February 2015}}<ref>{{Cite journal|last1=Snowdon|first1=Charles T.|last2=Pieper|first2=Bridget A.|last3=Boe|first3=Carla Y.|last4=Cronin|first4=Katherine A.|last5=Kurian|first5=Aimee V.|last6=Ziegler|first6=Toni E.|title=Variation in oxytocin is related to variation in affiliative behavior in monogamous, pairbonded tamarins|journal=Hormones and Behavior|volume=58|issue=4|pages=614–618|doi=10.1016/j.yhbeh.2010.06.014|pmid=20600045|pmc=2933949|year=2010|hdl=11858/00-001M-0000-0012-2863-F}}</ref>

Studies have shown that oxytocin is higher in monkeys in lifelong monogamous relationships compared to monkeys which are single. Furthermore, the oxytocin levels of the couples correlate positively; when the oxytocin secretion of one increases, the other one also increases. Higher levels of oxytocin are related to monkeys expressing more behaviours such as cuddling, grooming and sex, while lower levels of oxytocin reduce motivation for these activities.{{citation needed|date=February 2015}}

Research on oxytocin's role in the animal brain suggests that it plays less of a role in behaviours of love and affection than previously believed. "When oxytocin was first discovered in 1909, it was thought mostly to influence a mother's labour contractions and milk let-down. Then, in the 1990s, research with prairie voles found that giving them a dose of oxytocin resulted in the formation of a bond with their future mate (Azar, 40)." Oxytocin has since been treated by the media as the sole player in the "love and mating game" in mammals. This view, however, is proving to be false as, "most hormones don't influence behaviour directly. Rather, they affect thinking and emotions in variable ways (Azar, 40)." There is much more involved in sexual behaviour in the mammalian animal than oxytocin and vasopressin can explain.<ref>{{cite book |last= Lambert |first= K. |title= The Lab Rat Chronicles |year= 2011 |publisher= penguin group |location= New York |pages= 151–172}}</ref><ref>{{cite journal |last= Azar |first= B. |title= Oxytocin's other side |url= http://www.apa.org/monitor/2011/03/oxytocin.aspx |date= March 2011 |volume= 42 |issue= 3 |page= 40 |journal= Science Watch |access-date= 4 November 2012 |archive-date= 14 November 2012 |archive-url= https://web.archive.org/web/20121114151544/http://www.apa.org/monitor/2011/03/oxytocin.aspx |url-status= live }}</ref><ref>{{Cite journal | last1 = Aubert | first1 = Y. | last2 = Gustison | first2 = M. L. | last3 = Gardner | first3 = L. A. | last4 = Bohl | first4 = M. A. | last5 = Lange | first5 = J. R. | last6 = Allers | first6 = K. A. | last7 = Sommer | first7 = B. | last8 = Datson | first8 = N. A. | last9 = Abbott | first9 = D. H. | doi = 10.1111/j.1743-6109.2011.02616.x | title = Flibanserin and 8-OH-DPAT Implicate Serotonin in Association between Female Marmoset Monkey Sexual Behavior and Changes in Pair-Bond Quality | journal = The Journal of Sexual Medicine | volume = 9 | issue = 3 | pages = 694–707 | year = 2012 | pmid = 22304661| pmc = 5898967}}</ref><ref>{{Cite journal
| last1 = Gil | first1 = M. 
| last2 = Bhatt | first2 = R. 
| last3 = Picotte | first3 = K. B. 
| last4 = Hull | first4 = E. M. 
| title = Oxytocin in the medial preoptic area facilitates male sexual behavior in the rat 
| doi = 10.1016/j.yhbeh.2010.12.012 
| journal = Hormones and Behavior 
| volume = 59 
| issue = 4 
| pages = 435–443 
| year = 2011 
| pmid = 21195714 
| pmc =3081415 
}}</ref><ref>{{cite book |last= Scott |first= Graham |title= Essential Animal Behavior |year= 2004 |publisher= Wiley-Blackwell |isbn= 978-0632057993 |pages= 166–197}}</ref><ref>{{Cite journal 
| last1 = Agrati | first1 = D. 
| last2 = Fernández-Guasti | first2 = A. 
| last3 = Ferreño | first3 = M. 
| last4 = Ferreira | first4 = A. 
| title = Coexpression of sexual behavior and maternal aggression: The ambivalence of sexually active mother rats toward male intruders 
| doi = 10.1037/a0023085 
| journal = Behavioral Neuroscience 
| volume = 125 
| issue = 3 
| pages = 446–451 
| year = 2011 
| pmid = 21517149 
}}</ref><ref>{{Cite journal 
| last1 = McHenry | first1 = J. A. 
| last2 = Bell | first2 = G. A. 
| last3 = Parrish | first3 = B. P. 
| last4 = Hull | first4 = E. M. 
| title = Dopamine D1 receptors and phosphorylation of dopamine- and cyclic AMP-regulated phosphoprotein-32 in the medial preoptic area are involved in experience-induced enhancement of male sexual behavior in rats 
| doi = 10.1037/a0028707 
| journal = Behavioral Neuroscience 
| volume = 126 
| issue = 4 
| pages = 523–529 
| year = 2012 
| pmid = 22708956 
| pmc =3409344 
}}</ref><ref>{{Cite journal |last1=Matsushita |first1=Hiroaki |last2=Tomizawa |first2=Kazuhito |last3=Okimoto |first3=Naoki |last4=Nishiki |first4=Tei-ichi |last5=Ohmori |first5=Iori |last6=Matsui |first6=Hideki |date=2010-10-01 |title=Oxytocin mediates the antidepressant effects of mating behavior in male mice |url=https://www.sciencedirect.com/science/article/pii/S0168010210001641 |journal=Neuroscience Research |language=en |volume=68 |issue=2 |pages=151–153 |doi=10.1016/j.neures.2010.06.007 |pmid=20600375 |s2cid=207152048 |issn=0168-0102|url-access=subscription }}</ref><ref>{{Cite journal |last1=Phan |first1=Joseph |last2=Alhassen |first2=Lamees |last3=Argelagos |first3=Allan |last4=Alhassen |first4=Wedad |last5=Vachirakorntong |first5=Benjamin |last6=Lin |first6=Zitong |last7=Sanathara |first7=Nayna |last8=Alachkar |first8=Amal |date=2020-08-12 |title=Mating and parenting experiences sculpture mood-modulating effects of oxytocin-MCH signaling |journal=Scientific Reports |language=en |volume=10 |issue=1 |pages=13611 |doi=10.1038/s41598-020-70667-x |pmid=32788646 |pmc=7423941 |bibcode=2020NatSR..1013611P |issn=2045-2322}}</ref><ref>{{Cite journal |last1=Matsushita |first1=Hiroaki |last2=Sasaki |first2=Yuya |last3=Yunoki |first3=Aya |last4=Matsuji |first4=Ayuka |last5=Latt |first5=Hein Min |last6=Onishi |first6=Kazunari |last7=Tomizawa |first7=Kazuhito |last8=Matsui |first8=Hideki |date=2022-08-01 |title=Antidepressant-like effect of male mating behavior through oxytocin-induced CREB signaling |url=https://www.sciencedirect.com/science/article/pii/S0168010222001092 |journal=Neuroscience Research |language=en |volume=181 |pages=74–78 |doi=10.1016/j.neures.2022.04.002 |pmid=35421523 |s2cid=248089550 |issn=0168-0102|url-access=subscription }}</ref>

===Pleasure{{anchor|Sex for pleasure}}===
It is often assumed that animals do not have sex for pleasure, or alternatively that [[human]]s, [[pig]]s, [[bonobo]]s (and perhaps [[dolphin]]s and one or two more species of primates) are the only species that do. This is sometimes stated as "animals mate only for reproduction". This view is considered a misconception by some scholars.<ref>{{cite journal | last1 = Hull | first1 = Elaine M. | last2 = Meisel | first2 = R. L. | last3 = Sachs | first3 = B. D. | year = 2002 | title = Male sexual behavior | url = http://www.elaine-m-hull.com/publications/male_sex_beh_chap.pdf | journal = Hormones, Brain and Behavior | volume = 1 | pages = 3–137 | doi = 10.1016/B978-012532104-4/50003-2 | isbn = 9780125321044 | access-date = 13 August 2016 | archive-date = 1 August 2016 | archive-url = https://web.archive.org/web/20160801181028/http://www.elaine-m-hull.com/publications/male_sex_beh_chap.pdf | url-status = live }}</ref><ref name="Masson2009">{{cite book |author= Jeffrey Moussaieff Masson |title= When Elephants Weep: The Emotional Lives of Animals |url= https://books.google.com/books?id=TqxjMVBNEAsC&q=hyena%20ejaculated |access-date= 28 May 2013 |date= 21 October 2009 |publisher= Random House Publishing Group |isbn= 978-0-307-57420-6}}</ref> [[Jonathan Balcombe]] argues that the prevalence of non-reproductive sexual behaviour in certain species suggests that sexual stimulation is pleasurable. He also points to the presence of the [[clitoris]] in some female mammals, and evidence for female orgasm in primates.<ref>{{cite journal | author = Balcombe, J. | year = 2009 | title = Animal pleasure and its moral significance | journal = Applied Animal Behaviour Science | volume = 118 | issue = 3 | page = 212 | doi = 10.1016/j.applanim.2009.02.012 | s2cid = 16847348 | url = https://animalstudiesrepository.org/acwp_asie/5 | access-date = 6 July 2019 | archive-date = 2 May 2020 | archive-url = https://web.archive.org/web/20200502213716/https://animalstudiesrepository.org/acwp_asie/5/ | url-status = live | url-access = subscription }}</ref> On the other hand, it is impossible to know the subjective feelings of animals,<ref name="georgiadis" /> and the notion that [[emotion in non-human animals|non-human animals experience emotions]] similar to humans is a contentious subject.<ref name="Dawkins2000">{{cite journal|last=Dawkins|first=M.|year=2000|title=Animal minds and animal emotions|journal=American Zoologist|volume=40|issue=6|pages=883–888|doi=10.1668/0003-1569(2000)040[0883:amaae]2.0.co;2|s2cid=86157681 |url=https://animalstudiesrepository.org/cgi/viewcontent.cgi?article=1004&context=emotio |archive-url=https://web.archive.org/web/20200320083928/https://animalstudiesrepository.org/cgi/viewcontent.cgi?article=1004&context=emotio |url-status=dead |archive-date=20 March 2020 |url-access=subscription}}</ref><ref>{{cite journal|first=J.|last=Panksepp|title=Toward a general psychobiological theory of emotions|journal=Behavioral and Brain Sciences|volume=5|issue=3|year=1982|pages=407–422|doi=10.1017/S0140525X00012759|s2cid=145746882}}</ref><ref>{{cite web|url=http://www.bristol.ac.uk/news/2010/7165.html|title=Emotions help animals to make choices (press release)|year=2010|publisher=University of Bristol|access-date=26 October 2013|archive-date=4 October 2021|archive-url=https://web.archive.org/web/20211004071007/http://www.bristol.ac.uk/news/2010/7165.html|url-status=live}}</ref><ref>{{cite book|title=Animals, Ethics and Trade: The Challenge of Animal Sentience|editor1=Jacky Turner |editor2=Joyce D'Silva |year=2006|publisher=Earthscan|url=https://books.google.com/books?id=Jl6cejHNQQUC&q=animal%20emotions&pg=PA28|access-date=26 October 2013|isbn=9781844072545}}</ref>

A 2006 [[Denmark|Danish]] Animal Ethics Council report,<ref>Denmark, Det Dyreetiske Råd, ''[https://www.justitsministeriet.dk/sites/default/files/media/Pressemeddelelser/pdf/2006/Udtalelse.pdf Udtalelse om menneskers seksuelle omgang med dyr] {{Webarchive|url=https://web.archive.org/web/20211004053028/https://www.justitsministeriet.dk/sites/default/files/media/Pressemeddelelser/pdf/2006/Udtalelse.pdf |date=4 October 2021 }}'' (Copenhagen: Justitsministeriet, November 2006), p. 23–24. "Selv om det evolutionsmæssige formål med at parre sig kan siges at være reproduktion, er det ikke selve det, at dyrene får afkom, der i første omgang får dem til at parre sig. Det er til gengæld sandsynligt, at de parrer sig, fordi de er motiverede for selve parringsakten, og at denne er forbundet med en positiv oplevelse. Det er derfor rimeligt at antage, at der er en eller anden form for behag eller tilfredsstillelse forbundet med akten. Denne antagelse bekræftes af adfærden hos handyr, der for mange arters vedkommende er parate til at arbejde for at få adgang til hundyr, især hvis hundyret er i brunst, og handyr der i avlsøjemed er vant til at få tappet sæd – de viser stor ivrighed, når det udstyr, de forbinder med sædopsamlingen, tages frem. . . . Der er intet ved hunpattedyrenes anatomi eller fysiologi, der modsiger, at stimulation af kønsorganerne og parring skulle kunne være en positiv oplevelse – fx fungerer klitoris på samme måde som hos kvinder. Videnskabelige undersøgelser har vist, at reproduktionssuccesen forbedres ved stimulation af klitoris på bl.a. køer og hopper i forbindelse med insemination, fordi det forbedrer sædtransporten pga. sammentrækninger af de indre kønsdele. Dette gælder sandsynligvis også hundyr af andre dyrearter, og sammentrækninger i de indre kønsdele ses fx også under orgasme hos kvinder. Det er derfor rimeligt at antage, at det seksuelle samvær kan være forbundet med en positiv oplevelse for hundyrene."</ref> which examined current knowledge of animal sexuality in the context of legal queries concerning sexual acts by humans, has the following comments, primarily related to domestically common animals:

{{blockquote|Even though the evolution-related purpose of mating can be said to be reproduction, it is not actually the creating of offspring which originally causes them to mate. It is probable that they mate because they are motivated for the actual copulation, and because this is connected with a positive experience. It is therefore reasonable to assume that there is some form of pleasure or satisfaction connected with the act. This assumption is confirmed by the behaviour of males, who in the case of many species are prepared to work to get access to female animals, especially if the female animal is in oestrus, and males who for breeding purposes are used to [[semen collection|having sperm collected]] become very eager, when the equipment they associate with the collection is taken out. . . . There is nothing in [[female mammals]]' anatomy or physiology that contradicts that [[sexual stimulation|stimulation of the sexual organs]] and mating is able to be a positive experience. For instance, the clitoris acts in the same way as with women, and scientific studies have shown that the success of reproduction is improved by stimulation of clitoris on (among other species) cows and mares in connection with insemination, because it improves the transportation of the sperm due to contractions of the inner genitalia. This probably also applies to female animals of other animal species, and contractions in the inner genitals are seen e.g. also during orgasm for women. It is therefore reasonable to assume that sexual intercourse may be linked with a positive experience for female animals.}}

==Koinophilia==
{{Main|Koinophilia}}

Koinophilia is the love of the "normal" or phenotypically common (from the Greek {{Lang|grc|κοινός|size=90%}}, {{Lang|grc-Latn|koinós}}, meaning "usual" or "common").<ref name=Koeslag1990>{{cite journal | last1 = Koeslag | first1 = J.H. | year = 1990 | title = Koinophilia groups sexual creatures into species, promotes stasis, and stabilizes social behaviour | journal =Journal of Theoretical Biology | volume = 144 | issue = 1| pages = 15–35 | doi = 10.1016/S0022-5193(05)80297-8 | pmid=2200930| bibcode = 1990JThBi.144...15K }}</ref> The term was introduced to scientific literature in 1990, and refers to the tendency of animals seeking a mate to prefer that mate not to have any unusual, peculiar or deviant features.<ref name=Koeslag1990 /> Similarly, animals preferentially choose mates with low [[fluctuating asymmetry]].<ref name="Moller">{{cite journal|author1=Moller, A.P.  |author2=Pomiankowski, A |title=Fluctuating asymmetry and sexual selection|journal=Genetica|volume=89|issue=1–3 |pages=267–279|year=1993|doi=10.1007/bf02424520|s2cid=40071460 }}</ref> However, animal sexual ornaments can evolve through runaway selection, which is driven by (usually female) selection for non-standard traits.<ref name=Blind>Dawkins, Richard (1986). The Blind Watchmaker. Longman, London. Published in Penguin Books 1988, 1991, and 2006. Chapter 8, Explosions and Spirals.</ref>

==Interpretation bias==
The field of study of sexuality in non-human species was a long-standing [[taboo]].<ref name="news-medical">{{cite web |url= http://www.news-medical.net/news/2006/10/23/1500-animal-species-practice-homosexuality.aspx |title= 1,500 animal species practice homosexuality |date= 23 October 2006 |publisher= News-medical.net |access-date= 19 February 2007 |archive-date= 8 August 2014 |archive-url= https://web.archive.org/web/20140808051024/http://www.news-medical.net/news/2006/10/23/1500-animal-species-practice-homosexuality.aspx |url-status= live }}</ref>{{Unreliable source?|date=June 2010}} In the past, researchers sometimes failed to observe, miscategorised or misdescribed sexual behaviour which [[Observer bias|did not meet their preconceptions]]—their bias tended to support what would now be described as conservative sexual mores. An example of overlooking behaviour relates to descriptions of [[giraffe]] mating:

{{blockquote|When nine out of ten pairings occur between males, "[e]very male that sniffed a female was reported as sex, while [[anal sex|anal intercourse]] with [[orgasm]] between males was only [categorized as] 'revolving around' [[dominance (ethology)|dominance]], competition or greetings."<ref name="news-medical" />}}

In the 21st century, liberal social or sexual views are often projected upon animal subjects of research. Popular discussions of bonobos are a frequently cited example. Current research frequently expresses views such as that of the [[Natural History Museum at the University of Oslo]], which in 2006 held an exhibition on animal sexuality:

{{blockquote|Many researchers have described homosexuality as something altogether different from sex. They must realise that animals can have sex with who they will, when they will and without consideration to a researcher's ethical principles.<ref name="news-medical" />}}

Other animal activities may be misinterpreted due to the frequency and context in which animals perform the behaviour. For example, domestic ruminants display behaviours such as mounting and head-butting. This often occurs when the animals are establishing dominance relationships and are not necessarily sexually motivated. Careful analysis must be made to interpret what animal motivations are being expressed by those behaviours.<ref>{{Cite journal 
| doi = 10.1016/0093-691X(92)90233-H 
| last1 = Katz | first1 = L. S. 
| last2 = McDonald | first2 = T. J. 
| title = Sexual behavior of farm animals 
| journal = Theriogenology 
| volume = 38 
| issue = 2 
| pages = 239–253 
| year = 1992 
| pmid = 16727133
}}</ref>

==Types of sexual behaviour==

===Reproductive sexual behaviour===
====Copulation====
{{Main|Copulation (zoology)}}
Copulation is the union of the male and female [[sex organs]], the sexual activity specifically organized to transmit male sperm into the body of the female.<ref name="Knobil">Knobil E., Neill J.D. (Eds). [https://books.google.com/books?id=1_1cDe92k_YC The physiology of reproduction]. Academic Press, 3nd edition, 2005</ref>

====Cuckoldry====
[[File:BlueGill 002.jpg|thumb|right|Small male [[bluegill]] sunfishes [[cuckold]] large males by adopting ''sneaker'' strategies.]]
{{See also|Cuckoldry in fish}}

[[Alternative mating strategy|Alternative male strategies]] which allow small males to engage in [[cuckoldry]] can develop in species such as fish where [[spawning]] is dominated by large and aggressive males. Cuckoldry is a variant of [[Polyandry in nature|polyandry]], and can occur with ''sneak spawners''. A sneak spawner is a male that rushes in to join the spawning rush of a spawning pair.<ref>[http://www.fishbase.org/Glossary/Glossary.php?q=streak+spawning&language=english&sc=is Streak spawning] {{Webarchive|url=https://web.archive.org/web/20150210190505/http://www.fishbase.org/Glossary/Glossary.php?q=streak+spawning&language=english&sc=is |date=10 February 2015 }} Fishbase Glossary. Retrieved 11 February 2011.</ref> A spawning rush occurs when a fish makes a burst of speed, usually on a near vertical incline, releasing [[gamete]]s at the apex, followed by a rapid return to the lake or sea floor or fish aggregation.<ref>[http://www.fishbase.org/Glossary/Glossary.php?q=spawning+rush&language=english&sc=is Spawning rush] {{Webarchive|url=https://web.archive.org/web/20150210190502/http://www.fishbase.org/Glossary/Glossary.php?q=spawning+rush&language=english&sc=is |date=10 February 2015 }} Fishbase Glossary. Retrieved 11 February 2011.</ref> Sneaking males do not take part in courtship. In salmon and trout, for example, ''jack males'' are common. These are small silvery males that migrate upstream along with the standard, large, hook-nosed males and that spawn by sneaking into [[Spawn (biology)|redds]] to release sperm simultaneously with a mated pair. This behaviour is an [[evolutionarily stable strategy]] for reproduction, because it is favoured by natural selection just like the "standard" strategy of large males.<ref>Gross MR (1984) "Sunfish, salmon, and the evolution of alternative reproductive strategies and tactics in fishes". Pages 55–75 in GW Potts and RJ Wottoon, eds. ''Fish reproduction: Strategies and tactics''. Academic Press.</ref>

====Hermaphroditism====
[[File:Georgia Aquarium - Giant Grouper.jpg|thumb|right|Female [[grouper]]s change their sex to male if no male is available.]]
{{See also|Sequential hermaphroditism}}

[[Hermaphroditism]] occurs when a given individual in a species possesses both male and female reproductive organs, or can alternate between possessing first one, and then the other. Hermaphroditism is common in invertebrates but rare in vertebrates. It can be contrasted with [[gonochorism]], where each individual in a species is either male or female, and remains that way throughout their lives. Most fish are gonochorists, but hermaphroditism is known to occur in 14 families of [[teleost]] fishes.<ref name="Shapiro1984">Shapiro DY (1984) "Sex reversal and sociodemographics processes in coral reef fishes" Pages 103–116 in GW Potts and RK Wootoon, eds., ''Fish reproduction: Strategies and tactics'', Academic Press.</ref>

Usually hermaphrodites are ''[[Sequential hermaphroditism|sequential]]'', meaning they can [[Sequential hermaphroditism|switch sex]], usually from female to male ([[protogyny]]). This can happen if a dominant male is removed from a group of females. The largest female in the harem can switch sex over a few days and replace the dominant male.<ref name="Shapiro1984" /> This is found amongst [[coral reef fish]]es such as [[grouper]]s, [[parrotfish]]es and [[wrasse]]s. As an example, most [[wrasse]]s are [[protogynous]] hermaphrodites within a haremic mating system.<ref name="Robertson1978">{{Cite journal|last=Robertson|first=D.R.|author2=R.R. Warner|year=1978|title=Sexual patterns in the labroid fishes of the Western Caribbean II: the parrotfishes (Scaridae)|journal=Smithsonian Contributions to Zoology|volume=255|issue=255|pages=1–26|doi=10.5479/si.00810282.255}}</ref><ref name="Kazancioglu2010">{{Cite journal|last=Kazancioglu|first=E.|author2=S.H. Alonzo|date=August 2010|title=A comparative analysis of sex change in Labridae supports the size advantage hypothesis|journal=Evolution|volume=64|issue=8|pages=2254–2264|doi=10.1111/j.1558-5646.2010.01016.x|pmid=20394662|s2cid=8184412|doi-access=free}}</ref> It is less common for a male to switch to a female ([[protandry]]).<ref name="Moyle&Cech" />{{Rp|162}} A common example of a protandrous species are [[Amphiprioninae|clownfish]]—if the larger, dominant female dies, in many cases, the reproductive male gains weight and becomes the female.<ref>{{cite journal | last1 = Buston | first1 = Peter M. | title = Territory Inheritance in Clownfish | journal = Proceedings of the Royal Society B | volume = 271 | pages = S252–S254 | doi = 10.1098/rsbl.2003.0156 | pmid = 15252999 | pmc = 1810038 | date = May 2004 | issue = Suppl 4 }}</ref><ref>{{cite journal | last1 = Buston | first1 = P. | year = 2004| title = Does the Presence of Non-Breeders Enhance the Fitness of Breeders? An Experimental Analysis in the Clown Anemonefish ''Amphiprion percula'' | journal = Behavioral Ecology and Sociobiology | volume = 57 | issue = 1| pages = 23–31 | doi = 10.1007/s00265-004-0833-2 | bibcode = 2004BEcoS..57...23B | s2cid = 24516887 }}</ref> Hermaphroditism allows for complex mating systems. Wrasses exhibit three different mating systems: polygynous, [[Lek (biology)|lek-like]], and promiscuous mating systems.<ref name="Colin1992">{{Cite journal
  | last = Colin
  | first = P.L.
  |author2=L. J. Bell
   | title = Aspects of the spawning of labrid and scarid fishes (Pisces, Labroidei) at Enewetak Atoll, Marshall Islands with notes on other families (corrected reprint.)
  | journal = Environmental Biology of Fishes
  | volume = 33
  | issue = 3
  | pages = 330–345
  | doi = 10.1007/BF00005881
  | year = 1992
  | doi-access = free
  }}</ref>

====Sexual cannibalism====
{{Main|Sexual cannibalism}}
[[File:Araneus diadematus - mating behaviour - short.ogv|thumb|right|220px|Araneus diadematus – cannibalistic mating behaviour]]

Sexual cannibalism is a behaviour in which a female animal kills and consumes the male before, during, or after copulation. Sexual cannibalism confers fitness advantages to both the male and female.<ref>{{cite journal |last1=Zuk |first1=Marlene |title=Mates with Benefits: When and How Sexual Cannibalism Is Adaptive |journal=Current Biology |date=December 2016 |volume=26 |issue=23 |pages=R1230–R1232 |doi=10.1016/j.cub.2016.10.017 |pmid=27923131 |doi-access=free |bibcode=2016CBio...26R1230Z }}</ref> Sexual cannibalism is common among insects, arachnids<ref name="No7">{{cite journal | last1 = Polis | first1 = G.A. | year = 1981 | title = The evolution and dynamics of intraspecific +4193 predation | journal = Annual Review of Ecology and Systematics | volume = 51 | pages = 225–251 |doi=10.1146/annurev.es.12.110181.001301 | bibcode = 1981AnRES..12..225P | s2cid = 86286304 }}</ref> and [[Amphipoda|amphipods]].<ref name="No7" /> There is also evidence of sexual cannibalism in [[Gastropoda|gastropods]] and [[copepod]]s.<ref name="No8">{{cite journal | last1 = Bilde | first1 = T. | last2 = Tuni | first2 = C. | last3 = Elsayed | first3 = R. | last4 = Pekár | first4 = S. | last5 = Toft | first5 = S. | year = 2006 | title = Death feigning in the face of sexual cannibalism | journal = Biology Letters | volume = 2 | issue = 1| pages = 23–5 | doi=10.1098/rsbl.2005.0392 | pmid=17148316 | pmc=1617195}}</ref>

====Sexual coercion====
{{Main|Sexual coercion among animals}}
[[File: Safari Live Videos-Leopard Stories- Part 3 of 3- Tingana Mating.webm|thumb|right|220px|During mating, the male [[Leopard]] typically immobilizes the female]]

Sexual coercion behaviour during mating has been documented in a variety of species. In some [[herbivore|herbivorous]] herd species, or species where males and females are very different in size, the male [[dominance (ethology)|dominates]] sexually by force and size.{{Citation needed|date=November 2007}}

Some species of birds have been observed combining sexual intercourse with violence; these include [[duck]]s,<ref>{{cite journal |author1= Bailey, R.O. |author2= Seymour, N. R. |author3= Stewart, G.R. |title= Rape behaviour in blue-winged teal |journal= Auk |volume= 95 |issue= 1 |year= 1978 |pages= 188–90 |url= http://sora.unm.edu/sites/default/files/journals/auk/v095n01/p0188-p0190.pdf |doi= 10.2307/4085514 |jstor= 4085514 |access-date= 5 March 2013 |archive-date= 29 November 2014 |archive-url= https://web.archive.org/web/20141129150225/http://sora.unm.edu/sites/default/files/journals/auk/v095n01/p0188-p0190.pdf |url-status= live }}</ref><ref>{{Cite journal 
| last1 = Barash | first1 = D. P. 
| title = Sociobiology of Rape in Mallards (''Anas platyrhynchos''): Responses of the Mated Male 
| doi = 10.1126/science.197.4305.788 
| journal = Science 
| volume = 197 
| issue = 4305 
| pages = 788–789 
| year = 1977 
| pmid = 17790773 
|bibcode = 1977Sci...197..788B | s2cid = 34257131 
}}</ref> and [[geese]].<ref>{{Cite journal|last1=Mineau|first1=Pierre|last2=Cooke|first2=Fred|date=1979|title=Rape in the Lesser Snow Goose|journal=Behaviour|volume=70|issue=3|pages=280–291|doi=10.1163/156853979x00098|issn=0005-7959}}</ref> Female [[white-fronted bee-eater]]s are subjected to copulation. When females emerge from their nest burrows, males sometimes force them to the ground and mate with them. Such sexual coercion are made preferentially on females who are laying and who may therefore lay eggs fertilized by the male.<ref>{{Cite journal | last1 = Emlen | first1 = S. T. | last2 = Wrege | first2 = P. H. | doi = 10.1111/j.1439-0310.1986.tb00566.x | title = Forced Copulations and Intra-specific Parasitism: Two Costs of Social Living in the White-fronted Bee-eater | journal = Ethology | volume = 71 | pages = 2–29 | year = 2010 }}</ref>

It has been reported that young male elephants in South Africa sexually coerced and killed rhinoceroses.<ref>Siebert, Charles. (8 October 2006) [https://www.nytimes.com/2006/10/08/magazine/08elephant.html ''An Elephant Crackup?'', Charles Siebert, New York Times Magazine, 8 October 2006] {{Webarchive|url=https://web.archive.org/web/20121114151839/http://www.nytimes.com/2006/10/08/magazine/08elephant.html |date=14 November 2012 }}. Nytimes.com. Retrieved on 2011-12-22.</ref> This interpretation of the elephants' behaviour was disputed by one of the original study's authors, who said there was "nothing sexual about these attacks".<ref>{{cite web |url= http://www.straightdope.com/columns/read/2775/are-elephants-in-the-wild-showing-newly-aggressive-behavior-including-rape |title= Have elephants begun raping rhinos in the wild? |website= The Straight Dope |date= 25 July 2008 |access-date= 5 March 2013 |archive-date= 27 December 2012 |archive-url= https://web.archive.org/web/20121227090334/http://www.straightdope.com/columns/read/2775/are-elephants-in-the-wild-showing-newly-aggressive-behavior-including-rape |url-status= live }}</ref>

In elephant seals' sexual intercourse, male elephant seals have been known to have relations with penguins, attempting to copulate with them "several times with periods of rest in between". The birds remained pinned down for the duration. For female elephant seals, physical injury happens very often. Mating leads to 1 in every 1,000 female elephant seals getting killed.<ref name="nineteen" /> 

====Parthenogenesis====
[[Parthenogenesis]] is a form of asexual reproduction in which growth and development of embryos occur without fertilisation.<ref>{{Citation|last=Wininger|first=J. David|date=2004|pages=635–637|publisher=Elsevier|doi=10.1016/b978-012436643-5/50072-9|isbn=9780124366435|title=Handbook of Stem Cells|chapter=Parthenogenetic Stem Cells}}</ref> Technically, parthenogenesis is not a behaviour, however, sexual behaviours may be involved.

[[Cnemidophorus|Whip-tailed lizard]] females have the ability to reproduce through parthenogenesis and as such males are rare and sexual breeding non-standard. Females engage in "pseudocopulation"<ref name="Whiptail">{{cite web|url=http://www.todayifoundout.com/index.php/2011/05/the-new-mexico-whiptail-lizard-is-made-up-entirely-of-females/|title=New Mexico whiptail lizards are all females|author=Hiskey, D.|access-date=13 February 2015|date=2011-05-31|archive-date=13 February 2015|archive-url=https://web.archive.org/web/20150213144723/http://www.todayifoundout.com/index.php/2011/05/the-new-mexico-whiptail-lizard-is-made-up-entirely-of-females/|url-status=live}}</ref> to stimulate [[ovulation]], with their behaviour following their hormonal cycles; during low levels of oestrogen, these (female) lizards engage in "masculine" sexual roles. Those animals with currently high oestrogen levels assume "feminine" sexual roles. Lizards that perform the courtship ritual have greater fecundity than those kept in isolation due to an increase in hormones triggered by the sexual behaviours. So, even though 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.{{citation needed|date=February 2015}}

It is rare to find true parthenogenesis in fishes, where females produce female offspring with no input from males. All-female species include the Texas [[silverside (fish)|silverside]], ''Menidia clarkhubbsi''<ref>{{cite journal |vauthors=Echelle AA, Echelle AF, Crozier CD | year = 1983 | title = Evolution of an all-female fish, ''Menidia clarkhubbsi'' (Atherinidae) | journal = Evolution | volume = 37 | issue = 4| pages = 772–784 | doi = 10.2307/2407918 | pmid = 28568119 | jstor = 2407918}}</ref> and a complex of Mexican [[Poecilia|mollies]].<ref name="Moyle&Cech" />{{Rp|162}}

Parthenogenesis has been recorded in 70 vertebrate species<ref name="ScientificAmerican">{{cite magazine|author=Harmon, K.|title=No sex needed: All-female lizard species cross their chromosomes to make babies.|url=http://www.scientificamerican.com/article/asexual-lizards/|magazine=Scientific American|year=2010|access-date=13 February 2015}}</ref> including [[hammerhead shark]]s,<ref>{{Cite news|url=http://news.bbc.co.uk/2/hi/science/nature/6681793.stm|title=Captive shark had 'virgin birth'|access-date=23 December 2008|work=BBC News|date=2007-05-23|archive-date=17 December 2008|archive-url=https://web.archive.org/web/20081217051435/http://news.bbc.co.uk/2/hi/science/nature/6681793.stm|url-status=live}}</ref> [[blacktip shark]]s,<ref name="metro">{{Cite news| title='Virgin birth' for aquarium shark| url=http://www.metro.co.uk/weird/article.html?Virgin_birth_for_aquarium_shark&in_article_id=351241&in_page_id=2| publisher=[[Metro.co.uk]]| date=2008-10-10| access-date=2008-10-10| archive-date=11 October 2008| archive-url=https://web.archive.org/web/20081011190939/http://www.metro.co.uk/weird/article.html?Virgin_birth_for_aquarium_shark&in_article_id=351241&in_page_id=2| url-status=live}}</ref> amphibians<ref>{{Cite book
| editor-last = Halliday
| editor-first = Tim R.
| editor2-first = Kraig |editor2-last=Adler
| title = Reptiles & Amphibians
| publisher = Torstar Books
| year= 1986
| page = 101
| isbn = 978-0-920269-81-7}}</ref>
and lizards.<ref>{{cite news
| title = Scientists discover unknown lizard species at lunch buffet
| first = Brian
| last = Walker
| url = http://www.cnn.com/2010/LIVING/11/10/lizard.lunch.discovery/
| newspaper = CNN
| access-date = 2010-11-11
| date = 2010-11-11
| archive-date = 13 September 2018
| archive-url = https://web.archive.org/web/20180913002452/http://www.cnn.com/2010/LIVING/11/10/lizard.lunch.discovery/
| url-status = live
}}</ref>

====Unisexuality====
[[Unisexuality]] occurs when a species is all-male or all-female. Unisexuality occurs in some fish species and can take complex forms. ''[[Squalius alburnoides]]'', a minnow found in several river basins in Portugal and Spain, appears to be an all-male species. The existence of this species illustrates the potential complexity of mating systems in fish. The species originated as a hybrid between two species and is [[diploid]] but not hermaphroditic. It can have [[triploid]] and [[tetraploid]] forms, including all-female forms that reproduce mainly through [[hybridogenesis]].<ref>{{cite journal |vauthors=Alves MJ, Collarea-Pereira MJ, Dowling TE, Coelho MM | year = 2002 | title = The genetics of maintenance of an all-male lineage in the ''Squalius alburnoides'' complex | journal =Journal of Fish Biology | volume = 60 | issue = 3| pages = 649–662 | doi=10.1111/j.1095-8649.2002.tb01691.x| bibcode = 2002JFBio..60..649A }}</ref>

====Others====
[[File:The Clever Coyote (1951) Coyote dog mating.jpg|thumb|right|A dog mates with a coyote to produce a [[dog-coyote hybrid]].]]

* '''Interbreeding''': [[Hybrid (biology)|Hybrid]] offspring can result from the mating of two organisms of distinct but closely related parent species, although the resulting offspring is not always [[fertility|fertile]]. According to [[Alfred Kinsey]], genetic studies on wild animal populations have shown a "large number" of inter-species hybrids.<ref>{{cite book | author = Kinsey, Alfred | year = 1953 | title = Sexual Behavior in the Human Female | url = https://archive.org/details/sexualbehaviorin00inst | url-access = registration | page = [https://archive.org/details/sexualbehaviorin00inst/page/504 504] | publisher = W.B. Saunders Company}}</ref>
* '''Prostitution:''' There are reports that animals occasionally engage in [[Prostitution among animals|prostitution]]. A small number of pair-bonded females within a group of penguins took nesting material (stones) after copulating with a non-partner male. The researcher stated "I was watching opportunistically, so I can't give an exact figure of how common it really is."<ref>{{cite news |title= Penguins are turning to prostitution |publisher= BBC |date= 26 February 1998 |url= http://news.bbc.co.uk/2/hi/asia-pacific/60302.stm |access-date= 12 June 2008 |archive-date= 6 August 2017 |archive-url= https://web.archive.org/web/20170806115308/http://news.bbc.co.uk/2/hi/asia-pacific/60302.stm |url-status= live }}</ref> It has been reported that "bartering of meat for sex ... forms part of the social fabric of a troop of wild chimps living in the Tai National Park in the Côte d'Ivoire."<ref>{{cite news |url= https://www.independent.co.uk/news/science/sex-for-meat-ndash-how-chimps-seduce-their-mates-1665356.html |archive-url=https://ghostarchive.org/archive/20220507/https://www.independent.co.uk/news/science/sex-for-meat-ndash-how-chimps-seduce-their-mates-1665356.html |archive-date=7 May 2022 |url-access=subscription |url-status=live |location= London |work= The Independent |first= Steve |last= Connor |title= Sex for meat – how chimps seduce their mates |date= 8 April 2009}}{{cbignore}}</ref>
* '''Pavlovian conditioning:''' The sexualisation of objects or locations is recognised in the animal breeding world. For example, male animals may become [[sexual arousal|sexually aroused]] upon visiting a location where they have been allowed to have sex before, or upon seeing a stimulus previously associated with sexual activity such as an [[artificial vagina]].<ref name="animal ethics council">{{cite journal |author=Det Dyreetiske Råd |year=2006 |title=Udtalelse om menneskers seksuelle omgang med dyr |url=http://www.justitsministeriet.dk/fileadmin/downloads/Pressemeddelelser2006/d.pdf |url-status=dead |journal= |publisher=Justitsministeriet |archive-url=https://web.archive.org/web/20120227144357/http://www.justitsministeriet.dk/fileadmin/downloads/Pressemeddelelser2006/d.pdf |archive-date=27 February 2012 |quote='Selv om det evolutionsmæssige formål med at parre sig kan siges at være reproduktion, er det ikke selve det, at dyrene får afkom, der i første omgang får dem til at parre sig. Det er til gengæld sandsynligt, at de parrer sig, fordi de er motiverede for selve parringsakten, og at denne er forbundet med en positiv oplevelse. Det er derfor rimeligt at antage, at der er en eller anden form for behag eller tilfredsstillelse forbundet med akten. Denne antagelse bekræftes af adfærden hos handyr, der for mange arters vedkommende er parate til at arbejde for at få adgang til hundyr, især hvis hundyret er i brunst, og handyr der i avlsøjemed er vant til at få tappet sæd – de viser stor ivrighed, når det udstyr, de forbinder med sædopsamlingen, tages frem.' [Translation to English] 'Although the evolutionary purpose of mating can be said to be reproduction, it is not the very fact that animals have offspring that causes them to mate in the first place. Rather, it is likely that they mate because they are motivated by the act of mating itself and that this is associated with a positive experience. It is therefore reasonable to assume that there is some form of pleasure or satisfaction associated with the act. This assumption is confirmed by the behaviour of male animals, which for many species are prepared to work to gain access to females, especially if the female is in heat, and male animals which for breeding purposes are used to having their semen collected - they show great eagerness when the equipment they associate with semen collection is taken out.'}}</ref> Sexual preferences for certain cues can be artificially induced in rats by pairing scents or objects with their early sexual experiences.<ref name="pfaus">{{cite journal | author1 = Pfaus, J. G.|author2= Kippin, T. E.|author3= Coria-Avila, G. A.|author4= Gelez, H.|author5= Afonso, V. M.|author6= Ismail, N.|author7= Parada, M. | year = 2012 | title = Who, what, where, when (and maybe even why)? How the experience of sexual reward connects sexual desire, preference, and performance | journal = Archives of Sexual Behavior | volume = 41 | issue = 1 | pages = 31–62 | doi=10.1007/s10508-012-9935-5 | pmid=22402996|s2cid= 12421026}}</ref> The primary motivation of this behaviour is [[Pavlovian conditioning]], and the association is due to a conditioned response (or association) formed with a distinctive "reward".<ref name="pfaus" />
* '''Viewing images:''' A study using four adult male rhesus macaques (''Macaca mulatta'') showed that male [[rhesus macaque]]s will give up a highly valued item, juice, to see images of the faces or [[perineum]] of high-status females.<ref name="Deaner, Khera, Platt, 2005">{{cite journal|journal=Current Biology |author1=Deaner M. O. |author2=Khera A. V. |author3=Platt M. L. |year=2005 |title=Monkeys pay per view: adaptive valuation of social images by rhesus macaques |volume=15 |pages=543–548 |pmid=15797023 |doi=10.1016/j.cub.2005.01.044 |issue=6 |s2cid=1746276 |doi-access=free |bibcode=2005CBio...15..543D }}</ref> Encouraging captive [[giant panda|pandas]] to mate is problematic. Showing young male pandas "[[panda pornography]]" is credited with a recent population boom among pandas in captivity in China. One researcher attributed the success to the sounds on the recordings.<ref>Gray, Denis D. (27 November 2006) [http://www.nbcnews.com/id/15852885 Porn sparks panda baby boom in China: Research — and blue movies — attributed to record-high birth rate in 2006] {{Webarchive|url=https://web.archive.org/web/20200504203352/http://www.nbcnews.com/id/15852885 |date=4 May 2020 }}. Associated Press (via NBC News). Retrieved on 22 December 2011.</ref>
* '''Copulatory wounding and [[traumatic insemination]]''': Injury to a partner's genital tract during mating occurs in at least 40 taxa, ranging from fruit flies to humans. However, it often goes unnoticed due to its cryptic nature and because of internal wounds not visible outside.<ref>Klaus Reinhardt, Nils Anthes, and Rolanda Lange (2015) [http://cshperspectives.cshlp.org/content/7/5/a017582.abstract?etoc "Copulatory Wounding and Traumatic Insemination"] {{Webarchive|url=https://web.archive.org/web/20160111021916/http://cshperspectives.cshlp.org/content/7/5/a017582.abstract?etoc |date=11 January 2016 }} ''Cold Spring Harb Perspect Biol'' 2015; 7: a017582</ref>

===Non-reproductive sexual behaviour===
{{Main|Non-reproductive sexual behaviour in animals}}

There is a range of behaviours that animals perform that appear to be sexually motivated but which can not result in reproduction. These include:

* [[Masturbation in animals|Masturbation]]: Some species, both male and female, masturbate, both when partners are available and otherwise.<ref>{{Cite book |last=Würsig |first=Bernd |url=https://www.google.com/books/edition/Sex_in_Cetaceans/mfjYEAAAQBAJ?hl=en&gbpv=1&pg=PA164&printsec=frontcover |title=Sex in Cetaceans: Morphology, Behavior, and the Evolution of Sexual Strategies |last2=Orbach |first2=Dara N. |date=2023-09-25 |publisher=Springer Nature |isbn=978-3-031-35651-3 |language=en}}</ref><ref name="Watson1978">{{cite book |author= Watson, P. F. |title= Artificial breeding of non-domestic animals: (the proceedings of a symposium held at the Zoological Society of London on 7 and 8 September 1977) |url= https://books.google.com/books?id=kY8sZ7h4AEMC |access-date= 9 February 2013 |year= 1978 |publisher= Academic Press for the Zoological Society of London |isbn= 978-0-12-613343-1}}</ref><ref name="Balcombe2011">{{cite book |author= Balcombe, Jonathan P. |author-link=Jonathan Balcombe |title= The Exultant Ark: A Pictorial Tour of Animal Pleasure |url= https://books.google.com/books?id=tz9mSyTWh0oC&pg=PA89 |year= 2011 |publisher= University of California Press |isbn= 978-0-520-26024-5 |pages= 89–}}</ref>
* [[Oral sex in animals|Oral sex]]: Several species engage in both [[autofellatio]] and oral sex. This has been documented in [[brown bear]]s,<ref>[http://www.huffingtonpost.com/2014/06/17/brown-bear-oral-sex_n_5500255.html These Bears Are Having Lots Of Oral Sex, And Scientists Think They Know Why (The Huffington Post)] {{Webarchive|url=https://web.archive.org/web/20140714202344/http://www.huffingtonpost.com/2014/06/17/brown-bear-oral-sex_n_5500255.html |date=14 July 2014 }} By: Grenoble, Ryan.</ref> [[Tibetan macaques]],<ref name="Ogawa2006">{{cite book |author= Hideshi Ogawa |title= Wily Monkeys: Social Intelligence of Tibetan Macaques |url= https://books.google.com/books?id=EaKFLgm1TMUC&q=%22penis%22&pg=PA4 |year= 2006 |publisher= Kyoto University Press |isbn= 978-1-920901-97-4 |pages= 4–}}</ref> [[wolves]],<ref>{{cite journal |author= Fox, M. W. |jstor= 1379064 |title= The Social Significance of Genital Licking in the Wolf, ''Canis lupus'' |journal= Journal of Mammalogy |year= 1972 |pages= 637–640 |volume=53 |issue= 3 |doi=10.2307/1379064}}</ref> [[goat]]s, [[primate]]s, [[bat]]s,<ref>Sugita, Norimasa. [http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0166024 "Homosexual Fellatio: Erect Penis Licking between Male Bonin Flying Foxes Pteropus pselaphon."] {{Webarchive|url=https://web.archive.org/web/20171106062052/http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0166024 |date=6 November 2017 }} PLOS One 11.11 (2016): e0166024.</ref><ref>{{Cite journal 
| last1 = Tan | first1 = M. 
| last2 = Jones | first2 = G. 
| last3 = Zhu | first3 = G. 
| last4 = Ye | first4 = J. 
| last5 = Hong | first5 = T. 
| last6 = Zhou | first6 = S. 
| last7 = Zhang | first7 = S. 
| last8 = Zhang | first8 = L. 
| editor1-last = Hosken 
| editor1-first = David 
| doi = 10.1371/journal.pone.0007595 
| title = Fellatio by Fruit Bats Prolongs Copulation Time 
| journal = PLOS ONE 
| volume = 4 
| issue = 10 
| pages = e7595 
| year = 2009 
| pmid =  19862320
| pmc =2762080 
|bibcode = 2009PLoSO...4.7595T | doi-access = free 
}}</ref> [[cape ground squirrel]]s<ref>{{Cite journal | last1 = Waterman | first1 = J. M. | editor1-last = Briffa | editor1-first = Mark | title = The Adaptive Function of Masturbation in a Promiscuous African Ground Squirrel | doi = 10.1371/journal.pone.0013060 | journal = PLOS ONE | volume = 5 | issue = 9 | pages = e13060 | year = 2010 | pmid =  20927404| pmc =2946931 |bibcode = 2010PLoSO...513060W | doi-access = free }}</ref> and [[sheep]]. In the [[greater short-nosed fruit bat]], copulation by males is dorsoventral and the females lick the shaft or the base of the male's penis, but not the glans which has already penetrated the vagina. While the females do this, the penis is not withdrawn and research has shown a positive relationship between length of the time that the penis is licked and the duration of copulation. Post copulation genital grooming has also been observed.<ref name="plos">{{cite journal |doi=10.1371/journal.pone.0007595 |last= Tan |first= Min |author2= Gareth Jones |author3= Guangjian Zhu |author4= Jianping Ye |author5= Tiyu Hong |author6= Shanyi Zhou |author7= Shuyi Zhang |author8= Libiao Zhang |date= 28 October 2009 |title= Fellatio by Fruit Bats Prolongs Copulation Time |pages= e7595 |journal= PLOS ONE |volume= 4 |issue= 10 |pmid= 19862320 |pmc= 2762080 |bibcode= 2009PLoSO...4.7595T |editor1-last= Hosken |editor1-first= David|doi-access= free }}</ref>
* [[Homosexual behavior in animals|Homosexuality]]: Same-sex sexual behaviour occurs in a range of species, especially in social species, particularly in marine birds and mammals, monkeys, and the [[Hominidae|great apes]]. {{as of|1999}}, the scientific literature contained reports of homosexual behaviour in at least 471 wild species.<ref>{{cite book |ref= Bagemihl |author= Bagemihl, Bruce |year= 1999 |title= Biological Exuberance: Animal Homosexuality and Natural Diversity |url= https://archive.org/details/biologicalexuber00bage |url-access= registration |publisher= St. Martin's Press | page = [https://archive.org/details/biologicalexuber00bage/page/673 673]}}</ref> Organisers of the [[Against Nature?]] exhibit stated that "homosexuality has been observed among 1,500 species, and that in 500 of those it is well documented."<ref name="Oslo">{{cite news |url= http://news.bbc.co.uk/2/hi/europe/6066606.stm |title= Oslo gay animal show draws crowds |access-date= 19 October 2006 |date= 19 October 2006 |work= BBC News |archive-url= https://web.archive.org/web/20061029010417/http://news.bbc.co.uk/2/hi/europe/6066606.stm |archive-date= 29 October 2006 |url-status= live}}</ref> Besides humans, [[Homosexual behavior in sheep|sheep]] are the only known mammal to exhibit exclusive homosexual behavior.<ref name="Poiani2010">{{cite book| first1 = Aldo | last1 = Poiani | first2 = A. F. | last2 = Dixson |title=Animal Homosexuality: A Biosocial Perspective|url=https://books.google.com/books?id=EftT_1bsPOAC&pg=PA179|date=2010|publisher=[[Cambridge University Press]] |location=Cambridge, England |page=179|quote=This makes O. aries (ram) only the second mammal known, apart from humans, capable of displaying exclusive homosexuality.|isbn=9781139490382}}</ref>

[[File:Salvator merianae - necrophilia.jpg|thumb|A male [[Argentine black and white tegu|black and white tegu]] mounts a female that has been dead for two days and attempts to mate.<ref name="sazima">{{cite journal | author = Sazima, I. | year = 2015 | title = Corpse bride irresistible: a dead female tegu lizard (''Salvator merianae'') courted by males for two days at an urban park in South-eastern Brazil | journal = Herpetology Notes | volume = 8 | pages = 15–18 | url = http://www.biotaxa.org/hn/article/download/9131/11610 | access-date = 24 February 2015 | archive-date = 23 February 2015 | archive-url = https://web.archive.org/web/20150223235749/http://www.biotaxa.org/hn/article/download/9131/11610 | url-status = live }}</ref>]]
* [[Genital-genital rubbing]]: This is sexual activity in which one animal rubs his or her genitals against the genitals of another animal. This is stated to be the "bonobo's most typical sexual pattern, undocumented in any other primate".<ref name="songweaver">{{cite journal |author= de Waal FB |title= Bonobo sex and society |journal= [[Scientific American]] |volume= 272 |issue= 3 |pages= 82–8 |year= 1995 |pmid= 7871411 |quote= Perhaps the bonobo's most typical sexual pattern, undocumented in any other primate, is genito-genital rubbing (or GG rubbing) between adult females. One female facing another clings with arms and legs to a partner that, standing on both hands and feet, lifts her off the ground |doi= 10.1038/scientificamerican0395-82|bibcode= 1995SciAm.272c..82W }}</ref><ref>{{Cite journal 
| last1 = Paoli | first1 = T. 
| last2 = Palagi | first2 = E. 
| last3 = Tacconi | first3 = G. 
| last4 = Tarli | first4 = S. B. 
| title = Perineal swelling, intermenstrual cycle, and female sexual behavior in bonobos (''Pan paniscus'') 
| doi = 10.1002/ajp.20228 
| journal = American Journal of Primatology 
| volume = 68 
| issue = 4 
| pages = 333–347 
| year = 2006 
| pmid = 16534808 
| s2cid = 25823290 
}}</ref>
* [[Non-reproductive sexual behavior in animals#Cross-species sex|Inter-species mating]]: Some animals opportunistically mate with individuals of another species.<ref>Walker, Matt (2 May 2008) [http://news.bbc.co.uk/2/hi/science/nature/7379554.stm Science/Nature 'Sex pest' seal attacks penguin] {{Webarchive|url=https://web.archive.org/web/20080503124111/http://news.bbc.co.uk/2/hi/science/nature/7379554.stm |date=3 May 2008 }}. BBC News. Retrieved on 15 February 2011.</ref>
* [[Non-reproductive sexual behavior in animals#Sex involving juveniles|Sex involving juveniles]]: Male [[stoat]]s (''Mustela erminea'') will sometimes mate with infant females of their species.<ref>{{cite journal |author = Doncarlos, Michael W. |author2=Petersen, Jay S. |author3=Tilson, Ronald L. |title= Captive biology of an asocial mustelid; ''Mustela erminea'' |journal= Zoo Biology |volume= 5 |issue= 4 |pages= 363–370 |year= 1986 |doi= 10.1002/zoo.1430050407 }}</ref> This is a natural part of their reproductive biology—they have a [[delayed gestation]] period, so these females give birth the following year when they are fully grown. Juvenile male [[common chimpanzee]]s have been recorded mounting and copulating with immature chimps. Infants in [[bonobo]] societies are often involved in sexual behaviour.<ref name=ancestor>{{cite book |last= Dawkins |first= Richard |author-link= Richard Dawkins |title= The Ancestor's Tale |year= 2004 |publisher= Houghton Mifflin |chapter= Chimpanzees |isbn= 978-1-155-16265-2}}</ref>
* [[Necrophilia in animals|Necrophilia]]: This describes when an animal engages in a sexual act with a dead animal. It has been observed in mammals, birds, reptiles and frogs.<ref>{{cite journal | author1 = de Mattos Brito, L. B. | author2 = Joventino, I. R. | author3 = Ribeiro, S. C. | author4 = Cascon, P. | year = 2012 | title = Necrophiliac behavior in the "cururu" toad, ''Rhinella jimi'' Steuvax, 2002, (Anura, Bufonidae) from Northeastern Brazil | journal = North-Western Journal of Zoology | volume = 8 | issue = 2 | page = 365 | url = http://biozoojournals.ro/nwjz/content/v8n2/nwjz.121206.Brito.pdf | access-date = 5 February 2015 | archive-date = 5 February 2015 | archive-url = https://web.archive.org/web/20150205233901/http://biozoojournals.ro/nwjz/content/v8n2/nwjz.121206.Brito.pdf | url-status = live }}</ref>
* [[Bisexuality]]: This describes when an animal shows sexual behaviour towards both males and females.
* [[Extended female sexuality]]: This is when females mate with males outside of their conceptive period.<ref>{{cite book|last1=Thornhill|first1=R.|last2=Gangestad|first2=S. W.|title=The Evolutionary Biology of Human Female Sexuality|url=https://archive.org/details/evolutionarybiol00thor|url-access=limited|date=2008|publisher=Oxford University Press|location=USA|pages=[https://archive.org/details/evolutionarybiol00thor/page/n47 37]–55}}</ref><ref name="Fürtbauer-2011" />

====Seahorse====
[[Seahorse]]s, once considered to be monogamous species with pairs mating for life, were described in a 2007 study as "promiscuous, flighty, and more than a little bit gay".<ref name="seahorses">Simon De Bruxelles [https://www.thetimes.com/comment/register/article/promiscuous-and-bisexual-the-faithful-seahorse-has-a-secret-sex-life-f0bvwbzzlcz Promiscuous and bisexual — the 'faithful' seahorse has a secret sex life] . Timesonline.co.uk. 31 January 2007. Retrieved on 22 December 2011.</ref> Scientists at 15 [[aquarium|aquaria]] studied 90 seahorses of three species. Of 3,168 sexual encounters, 37% were same-sex acts. Flirting was common (up to 25 potential partners a day of both sexes); only one species (the British spiny seahorse) included faithful representatives, and for these 5 of 17 were faithful, 12 were not. Bisexual behaviour was widespread and considered "both a great surprise and a shock", with big-bellied seahorses of both sexes not showing partner preference. 1,986 contacts were male-female, 836 were female-female and 346 were male-male.<ref name="seahorses"/>

====Bonobo====
Among [[bonobo]]s, males and females [[sexual behavior of bonobos|engage in sexual behaviour]] with the same and the opposite sex, with females being particularly noted for engaging in sexual behaviour with each other and at up to 75% of sexual activity being non-reproductive, as being sexually active does not necessarily correlate with their ovulation cycles.<ref name="songweaver" /> Sexual activity occurs between almost all ages and sexes of bonobo societies.<ref>{{Cite journal 
| doi = 10.1159/000155465 
| last1 = Zihlman | first1 = A. L. 
| last2 = Hunter | first2 = W. S. 
| title = A biomechanical interpretation of the pelvis of Australopithecus 
| journal = Folia Primatologica 
| volume = 18 
| issue = 1 
| pages = 1–19 
| year = 1972 
| pmid = 4658666}}</ref><ref name="Hashimoto-1997">{{Cite journal|last=Hashimoto|first=Chie|date=1997|title=Context and Development of Sexual Behavior of Wild Bonobos (''Pan paniscus'') at Wamba, Zaire|journal=International Journal of Primatology|volume=18|issue=1|pages=1–21|doi=10.1023/a:1026384922066|s2cid=22744816|issn=0164-0291}}</ref> Primatologist Frans de Waal believes that bonobos use sexual activity to resolve conflict between individuals.<ref name=":2" /><ref>{{Cite journal|last1=Clay|first1=Zanna|last2=de Waal|first2=Frans B.M|date=2014|title=Sex and strife: post-conflict sexual contacts in bonobos|url=https://www.emory.edu/LIVING_LINKS/publications/articles/Clay_deWaal_2014.pdf|journal=Behaviour|volume=152|issue=3–4|pages=313–334|doi=10.1163/1568539X-00003155|access-date=18 November 2018|archive-date=5 February 2018|archive-url=https://web.archive.org/web/20180205143402/http://www.emory.edu/LIVING_LINKS/publications/articles/Clay_deWaal_2014.pdf|url-status=live}}</ref> Immature bonobos, contrariwise, perform genital contact when relaxed.<ref name="Hashimoto-1997" />

'''Macaque'''

Similar same-sex sexual behaviours occur in both male and female macaques.<ref name="Leca-2014">{{Cite journal|last1=Leca|first1=Jean-Baptiste|last2=Gunst|first2=Noëlle|last3=Vasey|first3=Paul L.|date=2014-05-28|title=Male Homosexual Behavior in a Free-Ranging All-Male Group of Japanese Macaques at Minoo, Japan|journal=Archives of Sexual Behavior|volume=43|issue=5|pages=853–861|doi=10.1007/s10508-014-0310-6|pmid=24867180|s2cid=30375191|issn=0004-0002}}</ref> It is thought to be done for pleasure as an erect male mounts and thrusts upon or into another male.<ref name="Leca-2014" /><ref name="Wallen-1997">{{Cite journal |url=https://www.researchgate.net/publication/13238242 |pmid=10051894 |access-date=2018-11-18|year=1997 |last1=Wallen |first1=K. |title=Sexual behavior in same-sexed nonhuman primates: Is it relevant to understanding human homosexuality? |journal=Annual Review of Sex Research |volume=8 |pages=195–223 |last2=Parsons |first2=W. A.|doi=10.1080/10532528.1997.10559922 }}</ref> Sexual receptivity can also be indicated by red faces and shrieking.<ref name="Leca-2014" /> Mutual ejaculation after a combination of anal intercourse and masturbation has also been witnessed, although it may be rare.<ref name="Wallen-1997" /> In comparison to socio-sexual behaviours such as dominance displays, homosexual mounts last longer, happen in series, and usually involve pelvic thrusting.<ref name="Leca-2014" />

Females are also thought to participate for pleasure as vulvar, perineal, and anal stimulation is part of these interactions. The stimulation can come from their own tails, mounting their partner, thrusting or a combination of these.<ref>{{Cite journal|url=https://www.researchgate.net/publication/6747847|title=Sexual Reward via Vulvar, Perineal, and Anal Stimulation: A Proximate Mechanism for Female Homosexual Mounting in Japanese Macaques {{!}} Request PDF|journal=Archives of Sexual Behavior|volume=35|issue=5|pages=523–532|language=en|access-date=2018-11-18|doi=10.1007/s10508-006-9111-x|pmid=17048107|year=2006|last1=Vasey|first1=Paul L.|last2=Duckworth|first2=Nadine|s2cid=24498074}}</ref>

====Dolphin{{anchor|Bottlenose dolphin|Bottlenose dolphins}}====
Male [[bottlenose dolphin]]s have been observed working in pairs to follow or restrict the movement of a female for weeks at a time, waiting for her to become sexually receptive. The same pairs have also been observed engaging in [[Reproductive organs of bottlenose dolphins|intense sexual play with each other]]. Janet Mann, a professor of biology and psychology at Georgetown University, argues<ref name="sfgate">
[http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2004/02/07/MNG3N4RAV41.DTL Central Park Zoo's gay penguins ignite debate] {{Webarchive|url=https://web.archive.org/web/20120612012603/http://www.sfgate.com/cgi-bin/article.cgi?f=%2Fc%2Fa%2F2004%2F02%2F07%2FMNG3N4RAV41.DTL |date=12 June 2012 }}. Sfgate.com (7 February 2004). Retrieved on 22 December 2011.</ref> that the common same-sex behaviour among male [[dolphin]] calves is about bond formation and benefits the species evolutionarily. Studies have shown the dolphins later in life are bisexual and the male bonds forged from homosexuality work for protection as well as locating females with which to reproduce.<ref name="sfgate"/>

In 1991, an English man was prosecuted for allegedly having sexual contact with a dolphin.<ref name="freddy">{{cite news |title= 'Tougher laws' to protect friendly dolphins |url= https://www.telegraph.co.uk/earth/earthnews/3322580/Tougher-laws-to-protect-friendly-dolphins.html |author= Unwin, Brian |date= 22 January 2008 |newspaper= [[The Daily Telegraph|The Telegraph]] |location= London |access-date= 4 April 2018 |archive-url= https://web.archive.org/web/20121227064311/http://www.telegraph.co.uk/earth/earthnews/3322580/Tougher-laws-to-protect-friendly-dolphins.html |archive-date= 27 December 2012 |url-status= dead}}</ref> The man was found not guilty after it was revealed at trial that the dolphin was known to tow bathers through the water by hooking his penis around them.<ref name="freddy"/>

====Hyena====
The female [[spotted hyena]] has [[Female genitalia of the spotted hyena|a unique urinary-genital system]], closely resembling the penis of the male, called a [[pseudo-penis]]. Dominance relationships with strong sexual elements are routinely observed between related females. They are notable for using visible sexual arousal as a sign of submission but not dominance in males as well as females (females have a sizeable erectile [[clitoris]]).<ref>{{cite journal |author1=East, Marion L. |author2=Hofer, Heribert |author3=Wickler, Wolfgang |journal= Behavioral Ecology and Sociobiology |year= 1993 |volume= 33 |issue= 6 |pages= 355–370 |title= The erect 'penis' is a flag of submission in a female-dominated society: greetings in Serengeti spotted hyenas |doi= 10.1007/BF00170251|bibcode=1993BEcoS..33..355E |s2cid=23727803 }}</ref> It is speculated that to facilitate this, their [[sympathetic nervous system|sympathetic]] and [[parasympathetic]] nervous systems may be partially reversed in respect to their reproductive organs.<ref>Sapolsky (1998), Why Zebras Don't Get Ulcers, W.H. Freeman and Co., {{ISBN|0-7167-3210-6}}, pp. 127–129.</ref>

==Mating behaviour==
{{See also|Mating call}}

===Vertebrates===

====Mammals====
{{Further|Mammalian reproduction|Social monogamy in mammalian species}}

Mammals mate by vaginal copulation. To achieve this, the male usually mounts the female from behind.<ref>Dewsbury, Donald A. "Patterns of copulatory behavior in male mammals." Quarterly Review of Biology (1972): 1-33.</ref> The female may exhibit [[lordosis behavior|lordosis]] in which she arches her back ventrally to facilitate entry of the penis, which is particularly present in elephants, [[felids]], and rodents. Amongst the land mammals, other than humans, only bonobos mate in a face-to-face position,<ref>{{cite web|url=http://www.cracked.com/article_15926_the-15-most-bizarre-animal-mating-rituals.html|title=The 15 most bizarre animal mating rituals|year=2008|author=Fortey, I.|access-date=18 February 2015|archive-date=18 February 2015|archive-url=https://web.archive.org/web/20150218180907/http://www.cracked.com/article_15926_the-15-most-bizarre-animal-mating-rituals.html|url-status=live}}</ref>{{better source needed|date=February 2015}} as the females' anatomy seems to reflect,<ref name="songweaver" /> although ventro-ventral copulation has also been observed in ''[[Rhabdomys]].''<ref>{{cite journal|title=Ventro–ventral copulation in a rodent: a female initiative? {{pipe}} Journal of Mammalogy {{pipe}} Oxford Academic |journal=Journal of Mammalogy |volume=96 |issue=5 |pages=1017–1023 |doi=10.1093/jmammal/gyv106 |year=2015 |last1=Dufour |first1=Claire M.-S. |last2=Pillay |first2=Neville |last3=Ganem |first3=Guila |doi-access=free }}</ref> Some sea mammals copulate in a belly-to-belly position.<ref name="ADW">{{cite web|title=''Tursiops aduncus'' Indo-Pacific bottlenose dolphin|url=http://animaldiversity.org/site/accounts/information/Tursiops%20aduncus.html|author=Diaz, K.|publisher=Animal Diversity Web|access-date=19 October 2016|archive-date=20 October 2016|archive-url=https://web.archive.org/web/20161020042349/http://animaldiversity.org/site/accounts/information/Tursiops%20aduncus.html|url-status=live}}</ref><ref name="Adul">{{cite journal|author1=Adulyanukosol, K.|author2= Thongsukdee, S.|author3= Hara, T.|author4= Arai, N.|author5=Tsuchiya, M.|year=2007|title=Observations of dugong reproductive behavior in Trang Province, Thailand: further evidence of intraspecific variation in dugong behavior|journal=Marine Biology|volume=151|issue=5|pages=1887–1891|doi=10.1007/s00227-007-0619-y|bibcode= 2007MarBi.151.1887A|s2cid= 86253387}}</ref> Some [[camelid]]s mate in a lying-down position.<ref name=sandiegozoo>{{cite web | publisher = San Diego Zoo Global Library | title = Bactrian & Dromedary Camels | work = Factsheets | access-date = 4 December 2012 | date = March 2009 | url = http://library.sandiegozoo.org/factsheets/camel/camel.htm | archive-url = https://web.archive.org/web/20120922092103/http://library.sandiegozoo.org/factsheets/camel/camel.htm | archive-date = 22 September 2012 | url-status = dead}}</ref> In most mammals ejaculation occurs after multiple intromissions,<ref>{{cite book|title=Encyclopedia of Behavioral Neuroscience|url=https://books.google.com/books?id=DfV-BwAAQBAJ&q=multiple%20intromission|date=16 April 2010|publisher=Elsevier Science|isbn=978-0-08-091455-8}}</ref> but in most primates, copulation consists of one brief intromission.<ref name="AltermanDoyle2013">{{cite book|author1=L. Alterman|author2=Gerald A. Doyle|author3=M.K. Izard|title=Creatures of the Dark|url=https://books.google.com/books?id=0U_uBwAAQBAJ&q=copulation%20OR%20intromission%20OR%20thrusting|date=9 March 2013|publisher=Springer Science & Business Media|isbn=978-1-4757-2405-9}}</ref> In most ruminant species, a single [[pelvic thrust]] occurs during copulation.<ref name="Noakes2009">{{cite book|author=David E. Noakes|title=Arthur's Veterinary Reproduction and Obstetrics|url=https://books.google.com/books?id=W5TdAwAAQBAJ&q=%22ejaculatory%20thrust%22|date=23 April 2009|publisher=Elsevier Health Sciences UK|isbn=978-0-7020-3990-4|pages=714–}}</ref><ref name="BroomFraser2007">{{cite book|author1=Donald M. Broom|author2=Andrew Ferguson Fraser|title=Domestic Animal Behaviour and Welfare|url=https://books.google.com/books?id=2XcMielOfHAC&q=mating%20mounting%20thrusting&pg=PA156|date=1 January 2007|publisher=CABI|isbn=978-1-84593-287-9|pages=156–}}</ref> In most deer species, a copulatory jump also occurs.<ref name="Geist1998">{{cite book|author=Valerius Geist|title=Deer of the World: Their Evolution, Behaviour, and Ecology|url=https://books.google.com/books?id=bcWZX-IMEVkC&q=(copulation%20OR%20coital%20OR%20intromission%20OR%20copulatory%20OR%20precopulatory%20OR%20postcopulatory%20OR%20mounting%20OR%20ejaculation)&pg=PA26|date=January 1998|publisher=Stackpole Books|isbn=978-0-8117-0496-0|pages=72–}}</ref><ref name="ShackletonMuseum1999">{{cite book|author1=David M. Shackleton|author2=Royal British Columbia Museum|title=Hoofed Mammals of British Columbia|url=https://books.google.com/books?id=iQq2iFktrwoC&q=(copulation%20OR%20coital%20OR%20intromission%20OR%20courtship%20OR%20copulatory%20OR%20precopulatory%20OR%20postcopulatory%20OR%20sexual%20OR%20mounting%20OR%20penis%20OR%20genitalia%20OR%20ejaculation)|year=1999|publisher=UBC Press|isbn=978-0-7748-0728-9}}</ref>

During mating, a "copulatory tie" occurs in mammals such as [[fossa (animal)|fossa]]s,<ref>{{Cite journal | doi=10.1007/s00265-014-1701-3|title = Polyandrous mating in treetops: How male competition and female choice interact to determine an unusual carnivore mating system| journal=Behavioral Ecology and Sociobiology| volume=68| issue=6| pages=879–889|year = 2014|last1 = Lührs|first1 = Mia-Lana| last2=Kappeler| first2=Peter M.| bibcode=2014BEcoS..68..879L |s2cid = 7995708}}</ref> [[canid]]s with the exception of [[African wild dogs]],<ref>{{cite journal | last1 = Dixson | first1 = A. F. | year = 1995 | title = Baculum length and copulatory behaviour in carnivores and pinnipeds (Grand Order Ferae) | url = https://www.researchgate.net/publication/229990265 | journal = Journal of Zoology | volume = 235 | issue = 1 | pages = 67–76 | doi = 10.1111/j.1469-7998.1995.tb05128.x | access-date = 27 August 2020 | archive-date = 3 June 2016 | archive-url = https://web.archive.org/web/20160603121320/https://www.researchgate.net/profile/Alan_Dixson/publication/229990265_Baculum_length_and_copulatory-behavior_in_carnivores_and_pinnipeds_(Grand_Order_Ferae)/links/5565173508ae94e957205686.pdf | url-status = live }}</ref> and [[Japanese marten]]s.<ref>{{cite journal | last1 = Tatara | first1 = Masaya | year = 1994 | title = Notes on the breeding ecology and behavior of Japanese martens on Tsushima Islands, Japan | url = https://scholar.google.com/scholar?start=10&q=%22copulatory+(tie%7Clock)%22 | journal = Journal of the Mammalogical Society of Japan | volume = 19 | issue = 1 | pages = 67–74 | access-date = 27 June 2017 | archive-date = 8 May 2022 | archive-url = https://web.archive.org/web/20220508210752/https://scholar.google.com/scholar?start=10&q=%22copulatory+(tie%7Clock)%22 | url-status = live }}</ref> A "copulatory lock" also occurs in some primate species, such as ''[[Galago senegalensis]].''<ref>{{cite journal | last1 = Dixson | first1 = Alan F | year = 1987 | title = Baculum length and copulatory behavior in primates | url = https://www.researchgate.net/publication/247964388| journal = American Journal of Primatology | volume = 13 | issue = 1| pages = 51–60 | doi = 10.1002/ajp.1350130107 | pmid = 31973483 | s2cid = 84028737 }}</ref>

The copulatory behaviour of many mammalian species is affected by [[sperm competition]].<ref>{{cite journal | last1 = Møller | first1 = A. P. | last2 = Birkhead | first2 = T. R. | year = 1989 | title = Copulation behaviour in mammals: evidence that sperm competition is widespread | url = https://academic.oup.com/biolinnean/article-pdf/38/2/119/14071594/j.1095-8312.1989.tb01569.x.pdf | journal = Biological Journal of the Linnean Society | volume = 38 | issue = 2| pages = 119–131 | doi = 10.1111/j.1095-8312.1989.tb01569.x}}</ref>

Some females have concealed fertility, making it difficult for males to evaluate if a female is fertile - humans are amongst these species. This is costly as ejaculation expends much energy.<ref name="Fürtbauer-2011" />

===Invertebrates===
{{See also|Mating of gastropods}}
[[File:Garden snails and love dart.jpg|thumb|Courting [[garden snail]]s. The one on the left has fired a [[love dart]] into the one on the right.]]
[[File:Stony coral spawning 2.jpg|thumb|right|A male [[Great star coral|star coral]] releases sperm into the water.]]

Invertebrates are often [[hermaphrodite]]s. Some hermaphroditic [[land snail]]s begin mating with an elaborate tactile courting ritual. The two snails circle around each other for up to six hours, touching with their tentacles, and biting lips and the area of the genital pore, which shows some preliminary signs of the eversion of the penis. As the snails approach mating, hydraulic pressure builds up in the blood sinus surrounding an organ housing a sharpened dart. The dart is made of [[calcium carbonate]] or [[chitin]], and is called a [[love dart]]. Each snail manoeuvres to get its genital pore in the best position, close to the other snail's body. Then, when the body of one snail touches the other snail's genital pore, it triggers the firing of the love dart.<ref>{{cite journal |doi=10.1007/s002650100345 |title=Dart receipt promotes sperm storage in the garden snail Helix aspersa |year=2001 |last1=Rogers |first1=David |last2=Chase |first2=Ronald |journal=Behavioral Ecology and Sociobiology |volume=50 |issue=2 |pages=122–7|bibcode=2001BEcoS..50..122R |s2cid=813656 }}</ref> After the snails have fired their darts, they copulate and exchange sperm as a separate part of the mating progression. The love darts are covered with a mucus that contains a [[hormone]]-like substance that facilitates the survival of the sperm.<ref>{{cite journal |author=Chase, R.| year=2007 |title=The function of dart shooting in helicid snails |journal=American Malacological Bulletin |volume=23 |pages=183–189 |doi=10.4003/0740-2783-23.1.183| s2cid=7562144 }}</ref><ref name="mcgill.ca">{{cite journal |author1=Chase, R. |author2=Blanchard, K. C. |year=2006 |url=https://www.mcgill.ca/newsroom/news/item/?item_id=19226 |title=The snail's love-dart delivers mucus to increase paternity |journal=Proceedings of the Royal Society of London B: Biological Sciences |volume=273 |number=1593 |pages=1471–1475 |doi=10.1098/rspb.2006.3474 |pmid=16777740 |pmc=1560308 |access-date=24 August 2017 |archive-date=18 November 2010 |archive-url=https://web.archive.org/web/20101118063022/http://www.mcgill.ca/newsroom/news/item/?item_id=19226 |url-status=live }}</ref>

[[Penis fencing]] is a mating behaviour engaged in by certain species of [[flatworm]], such as ''[[Pseudobiceros bedfordi]]''. Species which engage in the practice are hermaphroditic, possessing both eggs and sperm-producing testes.<ref>{{cite web |url= https://www.pbs.org/kcet/shapeoflife/episodes/hunt_explo2.html |title= Fighting to mate: flatworm penis fencing |author= Newman, Leslie |publisher= [[Public Broadcasting Service|PBS]] |access-date= 24 August 2017 |archive-date= 14 November 2013 |archive-url= https://web.archive.org/web/20131114002014/http://www.pbs.org/kcet/shapeoflife/episodes/hunt_explo2.html |url-status= dead }}</ref> The species "fence" using two-headed dagger-like penises which are pointed, and white in colour. One organism inseminates the other. The sperm is absorbed through pores in the skin, causing fertilisation.

[[Coral]]s can be both [[Gonochorism|gonochoristic]] (unisexual) and [[Hermaphroditism|hermaphroditic]], each of which can reproduce sexually and asexually. Reproduction also allows corals to settle new areas. Corals predominantly reproduce [[sexual reproduction|sexually]]. 25% of [[hermatypic coral]]s (stony corals) form single sex ([[gonochoristic]]) colonies, while the rest are [[hermaphroditic]].<ref name="Veron">{{cite book
 | author = Veron, J.E.N.
 | year = 2000
 | title = Corals of the World. Vol 3
 | edition = 3rd
 | publisher = Australian Institute of Marine Sciences and CRR Qld Pty Ltd.
 | location = Australia
 | isbn =  978-0-642-32236-4
}}</ref> About 75% of all hermatypic corals "broadcast spawn" by releasing [[gamete]]s{{snd}} [[egg (biology)|eggs]] and [[sperm]]{{snd}} into the water to spread offspring. The gametes fuse during fertilisation to form a microscopic [[larva]] called a [[planula]], typically pink and elliptical in shape.<ref name=Barnes99>
{{cite book
 | last1= Barnes |first1=R. and |first2=R. |last2=Hughes
 | year = 1999
 | title = An Introduction to Marine Ecology
 | edition = 3rd
 | pages = 117–141
 | publisher = Blackwell Science, Inc.
 | location = Malden, MA
 | isbn = 978-0-86542-834-8
}}</ref> [[Reproductive synchrony|Synchronous spawning]] is very typical on the coral reef and often, even when multiple [[species]] are present, all corals spawn on the same night. This synchrony is essential so that male and female gametes can meet. Corals must rely on environmental cues, varying from species to species, to determine the proper time to release gametes into the water. The cues involve lunar changes, sunset time, and possibly chemical signalling.<ref name="Veron" /> Synchronous spawning may form hybrids and is perhaps involved in coral [[speciation]].<ref name=Hatta>
{{cite journal
 | author1 = Hatta, M.
 | author2 = Fukami, H.
 | author3 =  Wang, W.
 | author4 =  Omori, M.
 | author5 = Shimoike, K.
 | author6 =  Hayashibara, T.
 | author7 = Ina, Y.
 | author8 =  Sugiyama, T.
 | title=Reproductive and genetic evidence for a reticulate evolutionary theory of mass spawning corals
 | journal=Molecular Biology and Evolution
 | year=1999
 | pages=1607–1613
 | volume=16
 | issue=11
 | pmid=10555292
 | doi=10.1093/oxfordjournals.molbev.a026073
| doi-access=free
 }}</ref>

Butterflies spend much time searching for mates. When the male spots a mate, he will fly closer and release [[pheromone]]s. He then performs a special [[courtship dance]] to attract the female. If the female appreciates the dancing she may join him. Then they join their bodies together end to end at their [[abdomen]]s. Here, the male passes the sperm to the female's egg-laying tube, which will soon be fertilised by the sperm.<ref>{{cite web |url= http://scienceray.com/biology/zoology/13-strangest-and-most-unusual-sexual-behavior-among-the-animals/2/ |title= Chan Lee Peng, August 2008 |publisher= Scienceray.com |access-date= 5 March 2013 |archive-date= 1 February 2013 |archive-url= https://web.archive.org/web/20130201145720/http://scienceray.com/biology/zoology/13-strangest-and-most-unusual-sexual-behavior-among-the-animals/2/ |url-status= live }}</ref>

Many animals make [[copulatory plug|plugs of mucus]] to seal the female's [[Body orifice|orifice]] after mating. Normally such plugs are secreted by the male, to block subsequent partners. In spiders the female can assist the process.<ref name=Economist>{{Cite news |title= Sexual Appetite and Animal behaviour – Sex and the single spider |newspaper= The Economist |url= http://www.economist.com/node/18956086 |date= 14 July 2011 |volume= 400 |issue= 8742 |access-date= 3 May 2013 |archive-date= 4 June 2013 |archive-url= https://web.archive.org/web/20130604062257/http://www.economist.com/node/18956086 |url-status= live }}</ref> Spider sex is unusual in that males transfer their sperm to the female on small limbs called pedipalps. They use these to pick their sperm up from their genitals and insert it into the female's sexual orifice, rather than copulating directly.<ref name=Economist/> On the 14 occasions a sexual plug was made, the female produced it without assistance from the male. On ten of these occasions the male's pedipalps then seemed to get stuck while he was transferring the sperm (which is rarely the case in other species of spider), and he had great difficulty freeing himself. In two of those ten instances, he was eaten as a result.<ref name=Economist/>

In the orb-weaving spider species ''[[Zygiella x-notata]]'', individuals engage in a variety of sexual behaviors including male choosiness, mate guarding, and vibrational signaling in courtship.<ref>{{Cite journal|last1=Bel-Venner|first1=M.c|last2=Dray|first2=S|last3=Allainé|first3=D|last4=Menu|first4=F|last5=Venner|first5=S|date=2008-01-07|title=Unexpected male choosiness for mates in a spider|url= |journal=Proceedings of the Royal Society B: Biological Sciences|volume=275|issue=1630|pages=77–82|doi=10.1098/rspb.2007.1278|pmc=2562406|pmid=17956845}}</ref><ref>{{Cite journal|last1=Bel-Venner|first1=M. C.|last2=Venner|first2=S.|date=2006-06-01|title=Mate-guarding strategies and male competitive ability in an orb-weaving spider: results from a field study|url=http://www.sciencedirect.com/science/article/pii/S0003347206000972|journal=Animal Behaviour|language=en|volume=71|issue=6|pages=1315–1322|doi=10.1016/j.anbehav.2005.08.010|s2cid=53195526|issn=0003-3472|url-access=subscription}}</ref>

==Genetic evidence of interspecies sexual activity in humans==
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THIS SECTION IS SEPARATED FROM THE MAIN "INTERSPECIES SEXUAL ACTIVITY" SECTION, IN ORDER TO AVOID CONFUSING TWO ISSUES: ANIMAL SEXUALITY (WHICH IS NOT SO CONTROVERSIAL) AND HUMAN EVOLUTION/HUMAN/CHIMP SEX (WHICH TO SOME PEOPLE IS).
SEE TALK PAGE.
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{{Main|Humanzee}}
Research into [[human evolution]] confirms that, in some cases, interspecies sexual activity may have been responsible for the evolution of new species ([[speciation]]). Analysis of animal [[gene]]s found evidence that, after [[human]]s had diverged from other [[ape]]s, interspecies mating nonetheless occurred regularly enough to change certain genes in the new [[gene pool]].<ref name="Patterson2006">{{cite journal |last= Patterson |first= Nick |author2= Daniel J. Richter |author3= Sante Gnerre |author4= Eric S. Lander |author5= David Reich |date= 29 June 2006 |title= Genetic evidence for complex speciation of humans and chimpanzees |journal= Nature |volume= 441 |issue= 7097 |pages= 1103–1108 |issn= 0028-0836 |doi= 10.1038/nature04789 |pmid= 16710306 |bibcode= 2006Natur.441.1103P |s2cid= 2325560 }}</ref> Researchers found that the [[X chromosome]]s of humans and chimps may have [[genetic divergence|diverged]] around 1.2 million years after the other chromosomes. One possible explanation is that modern humans emerged from a hybrid of human and chimp populations.<ref name=NYTWade2006>Wade, Nicholas (18 May 2006) [https://www.nytimes.com/2006/05/18/science/18evolve.html Two Splits Between Human and Chimp Lines Suggested] {{Webarchive|url=https://web.archive.org/web/20220518095858/https://www.nytimes.com/2006/05/18/science/18evolve.html |date=18 May 2022 }}, ''New York Times''.</ref> A 2012 study questioned this explanation, concluding that "there is no strong reason to involve complicated factors in explaining the autosomal data".<ref name="Yamamichi2012">{{cite journal |last= Yamamichi |first= M |author2= Gojobori J |author3= Innan H. |date= Jan 2012 |title= An autosomal analysis gives no genetic evidence for complex speciation of humans and chimpanzees |journal= Mol Biol Evol |volume= 29 |issue= 1 |pages= 145–56 |doi= 10.1093/molbev/msr172 |pmid= 21903679 |pmc=3299331}}</ref>{{Dubious |1=Genetic evidence of interspecies sexual activity in humans: autosomes do not include the X|date=August 2019}}

==Inbreeding avoidance==
{{Main|Inbreeding avoidance}}

When close relatives mate, progeny may exhibit the detrimental effects of [[inbreeding depression]]. Inbreeding depression is predominantly caused by the [[homozygous]] expression of recessive deleterious alleles.<ref name="pmid19834483">{{cite journal |vauthors=Charlesworth D, Willis JH |title=The genetics of inbreeding depression |journal=Nature Reviews Genetics |volume=10 |issue=11 |pages=783–96 |year=2009 |pmid=19834483 |doi=10.1038/nrg2664 |s2cid=771357 }}</ref> Over time, inbreeding depression may lead to the evolution of [[inbreeding avoidance]] behaviour. Several examples of animal behaviour that reduce mating of close relatives and inbreeding depression are described next.

Reproductively active female [[naked mole-rat]]s tend to associate with unfamiliar males (usually non-kin), whereas reproductively inactive females do not discriminate.<ref name="pmid10584337">{{cite journal |vauthors=Clarke FM, Faulkes CG |title=Kin discrimination and female mate choice in the naked mole-rat Heterocephalus glaber |journal=Proc. Biol. Sci. |volume=266 |issue=1432 |pages=1995–2002 |year=1999 |pmid=10584337 |pmc=1690316 |doi=10.1098/rspb.1999.0877}}</ref> The preference of reproductively active females for unfamiliar males is interpreted as an adaptation for avoiding inbreeding.

When mice inbreed with close relatives in their natural habitat, there is a significant detrimental effect on progeny survival.<ref name="pmid7939661">{{cite journal|author-link2=Kimberly Hughes |vauthors=Jiménez JA, Hughes KA, Alaks G, Graham L, Lacy RC |title=An experimental study of inbreeding depression in a natural habitat |journal=Science |volume=266 |issue=5183 |pages=271–3 |year=1994 |pmid=7939661 |doi= 10.1126/science.7939661|bibcode=1994Sci...266..271J}}</ref> In the house mouse, the [[Major urinary proteins|major urinary protein]] (MUP) gene cluster provides a highly polymorphic scent signal of genetic identity that appears to underlie [[kin recognition]] and [[inbreeding avoidance]]. Thus there are fewer matings between mice sharing MUP [[haplotype]]s than would be expected if there were random mating.<ref name="pmid17997307">{{cite journal |vauthors=Sherborne AL, Thom MD, Paterson S, Jury F, Ollier WE, Stockley P, Beynon RJ, Hurst JL |title=The genetic basis of inbreeding avoidance in house mice |journal=Curr. Biol. |volume=17 |issue=23 |pages=2061–6 |year=2007 |pmid=17997307 |pmc=2148465 |doi=10.1016/j.cub.2007.10.041|bibcode=2007CBio...17.2061S }}</ref>

[[Meerkat]] females appear to be able to discriminate the odour of their kin from the odour of their non-kin.<ref name="pmid23234867">{{cite journal |vauthors=Leclaire S, Nielsen JF, Thavarajah NK, Manser M, Clutton-Brock TH |title=Odour-based kin discrimination in the cooperatively breeding meerkat |journal=Biology Letters |volume=9 |issue=1 |page=20121054 |year=2013 |pmid=23234867 |pmc=3565530 |doi=10.1098/rsbl.2012.1054 }}</ref> Kin recognition is a useful ability that facilitates both cooperation among relatives and the avoidance of inbreeding. When mating does occur between meerkat relatives, it often results in [[inbreeding depression]]. Inbreeding depression was evident for a variety of traits: pup mass at emergence from the natal burrow, hind-foot length, growth until independence and juvenile survival.<ref name="pmid22497583">{{cite journal |vauthors=Nielsen JF, English S, Goodall-Copestake WP, Wang J, Walling CA, Bateman AW, Flower TP, Sutcliffe RL, Samson J, Thavarajah NK, Kruuk LE, Clutton-Brock TH, Pemberton JM |title=Inbreeding and inbreeding depression of early life traits in a cooperative mammal |journal=Mol. Ecol. |volume=21 |issue=11 |pages=2788–804 |year=2012 |pmid=22497583 |doi=10.1111/j.1365-294X.2012.05565.x |bibcode=2012MolEc..21.2788N |hdl=2263/19269 |s2cid=36059683 |hdl-access=free }}</ref>

The [[Grey red-backed vole|grey-sided vole]] (''Myodes rufocanus'') exhibits male-biased dispersal as a means of avoiding incestuous matings.<ref name="pmid19140979">{{cite journal |vauthors=Ishibashi Y, Saitoh T |title=Role of male-biased dispersal in inbreeding avoidance in the grey-sided vole (Myodes rufocanus) |journal=Mol. Ecol. |volume=17 |issue=22 |pages=4887–96 |year=2008 |pmid=19140979 |doi=10.1111/j.1365-294X.2008.03969.x |bibcode=2008MolEc..17.4887I |s2cid=44992920 }}</ref> Among those matings that do involve inbreeding the number of weaned juveniles in litters is significantly smaller than that from non-inbred litters indicating inbreeding depression.

In natural populations of the bird ''[[Parus major]]'' (great tit), inbreeding is likely avoided by dispersal of individuals from their birthplace, which reduces the chance of mating with a close relative.<ref name="pmid18211876">{{cite journal |vauthors=Szulkin M, Sheldon BC |title=Dispersal as a means of inbreeding avoidance in a wild bird population |journal=Proc. Biol. Sci. |volume=275 |issue=1635 |pages=703–11 |year=2008 |pmid=18211876 |pmc=2596843 |doi=10.1098/rspb.2007.0989}}</ref> Dispersing to avoid inbreeding is a common behavior amongst animals, such as [[Felidae|felids]] and [[Canidae|canids]], although inbreeding can still occur, albeit rarely.

[[Toad]]s display [[Philopatry#Breeding-site philopatry|breeding site fidelity]], as do many [[amphibian]]s. Individuals that return to natal ponds to breed will likely encounter [[sibling]]s as potential mates. Although [[incest]] is possible, ''Bufo americanus'' siblings rarely mate. These toads likely recognise and actively avoid close kins as mates. Advertisement vocalisations by males appear to serve as cues by which females recognise their kin.<ref>{{cite journal | last1 = Waldman | first1 = B | last2 = Rice | first2 = JE | last3 = Honeycutt | first3 = RL | year = 1992 | title = Kin recognition and incest avoidance in toads | journal = Am. Zool. | volume = 32 | pages = 18–30 | doi=10.1093/icb/32.1.18| doi-access = free }}</ref>

==See also==
{{Portal|Animals}}
* [[Reproductive isolation#Pre-copulatory mechanisms in animals|Pre-copulatory isolation mechanisms in animals]]
* [[Biology and sexual orientation]]
* ''[[Green Porno]]'', a series of short films about animal mating, enacted by humans, airing on the [[Sundance Channel (United States)|Sundance Channel]]
* [[List of animals displaying homosexual behaviour]]
* [[r/K selection theory]]
* {{section link|House mouse|Social behavior}} includes polygamy
* [[Sexual behavior of dogs]]
* [[Sexual behavior of horses]]
* [[Non-reproductive sexual behavior in animals]]
* {{annotated link|Sequential hermaphroditism}}

==References==
{{Reflist}}

==Bibliography==
* {{cite book |ref= Bagemihl |author= Bagemihl, Bruce |year= 1999 |url= https://books.google.com/books?id=tmFJ1LhbVWcC |title= Biological Exuberance: Animal Homosexuality and Natural Diversity |publisher= St. Martin's Press |isbn= 978-0-312-19239-6 }}
* {{cite book |ref= Schaller |author= Schaller, G.B. |title= The Serengeti Lion |publisher= University of Chicago Press |year= 1972 |isbn= 978-0226736600}}

==Further reading==
*{{cite book|author=R. F. Ewer|title=Ethology of Mammals|url=https://books.google.com/books?id=0LTzBwAAQBAJ&q=mating%20OR%20intromission%20OR%20copulation%20OR%20coitus%20OR%20%22sexual%20behavior%22|date=11 December 2013|publisher=Springer|isbn=978-1-4899-4656-0}}
* {{cite book |first1=Ronald D. |last1=Nadler |year=1980 |chapter-url=https://pubmed.ncbi.nlm.nih.gov/6934312/ |chapter=Reproductive physiology and behaviour of gorillas |editor-first1=R. V. |editor-last1=Short |editor-first2=Barbara J. |editor-last2=Weir |title=The Great Apes of Africa |journal=Journal of Reproduction and Fertility. Supplement |volume=Suppl 28 |pages=59–70 |location=Cambridge |publisher=Journals of Reproduction and Fertility Ltd. |pmid=6934312 |isbn=978-0906545041}}
* {{cite book |author= Richard Estes |title= The Behavior Guide to African Mammals: Including Hoofed Mammals, Carnivores, Primates |url= https://books.google.com/books?id=g977LsZHpcsC&q=intromission%20OR%20copulation%20OR%20coitus%20OR%20ejaculation%20OR%20%22sexual%20behavior%22 |year= 1991 |publisher= University of California Press |isbn= 978-0-520-08085-0}}
* {{cite book|author1=William F. Perrin|author2=Bernd Wursig|author3=J.G.M. 'Hans' [[Hans Thewissen|Thewissen]]|title=Encyclopedia of Marine Mammals|url=https://books.google.com/books?id=2rkHQpToi9sC&q=mating%20OR%20intromission%20OR%20copulation%20OR%20coitus%20OR%20%22sexual%20behavior%22|date=26 February 2009|publisher=Academic Press|isbn=978-0-08-091993-5}}
* {{cite book |title=Evolution's Rainbow: Diversity, Gender, and Sexuality in Nature and People |year=2013 |first=Joan |last=Roughgarden |publisher=University of California Press |isbn=978-0520280458}}
* {{cite book |author= John Vandenbergh |title= Pheromones and Reproduction in Mammals |url= https://books.google.com/books?id=PUpYID8Rc3UC |date= 28 August 1983 |publisher= Elsevier |isbn= 978-0-323-15651-6}}
* {{cite book|author1=Temple Grandin|author2=Mark J. Deesing|title=Genetics and the Behavior of Domestic Animals|url=https://books.google.com/books?id=4L3dMJ8-aWgC&q=ejaculation%20OR%20mating%20OR%20copulation%20OR%20intromission%20OR%20%22sexual%20behavior%22%20OR%20coitus|date=22 April 2013|publisher=Academic Press|isbn=978-0-12-405508-7}}
* {{cite book|author1=Menna Jones|author2=Chris R. Dickman|author3=Michael Archer|title=Predators with Pouches: The Biology of Carnivorous Marsupials|url=https://books.google.com/books?id=3YQSDiWHfD0C&q=mating%20OR%20intromission%20OR%20copulation%20OR%20coitus%20OR%20ejaculation%20OR%20%22sexual%20behavior%22%20OR%20estrus|year=2003|publisher=Csiro Publishing|isbn=978-0-643-06634-2}}
*{{cite book|author=Ernst Knobil|title=Knobil and Neill's Physiology of Reproduction|url=https://books.google.com/books?id=11f2zMjqqVkC&q=(copulation%20OR%20coital%20OR%20intromission%20OR%20courtship%20OR%20copulatory%20OR%20precopulatory%20OR%20postcopulatory%20OR%20%22sexual%20behavior%22%20OR%20%22reproductive%20behavior%22%20OR%20mounting)|year=2006|publisher=Gulf Professional Publishing|isbn=978-0-12-515402-4}}
; Sexual behavior of horses
* {{cite book|author=Morel, M.C.G.D.|title=Equine Reproductive Physiology, Breeding and Stud Management|url=https://books.google.com/books?id=iz1C6pSwq40C&q=(copulation%20OR%20coital%20OR%20intromission%20OR%20courtship%20OR%20copulatory%20OR%20precopulatory%20OR%20postcopulatory%20OR%20sexual%20OR%20mounting%20OR%20ejaculation)|year=2008|publisher=CABI|isbn=978-1-78064-073-0}}
* {{cite book|author1=D. S. Mills|author2=S. M. McDonnell|title=The Domestic Horse: The Origins, Development and Management of Its Behaviour|url=https://books.google.com/books?id=GHKuEeqC4U0C&q=(copulation%20OR%20coital%20OR%20intromission%20OR%20courtship%20OR%20copulatory%20OR%20precopulatory%20OR%20postcopulatory%20OR%20sexual%20OR%20mounting%20OR%20penis%20OR%20genitalia%20OR%20ejaculation)&pg=PA110|date=10 March 2005|publisher=Cambridge University Press|isbn=978-0-521-89113-4|pages=110–}}
*{{cite book|author1=Jonathan Pycock|author2=Juan C. Samper|author3=Angus O. McKinnon|title=Current Therapy in Equine Reproduction E-Book|url=https://books.google.com/books?id=d2ac2NPLxsQC&q=(copulation%20OR%20coital%20OR%20intromission%20OR%20courtship%20OR%20copulatory%20OR%20precopulatory%20OR%20postcopulatory%20OR%20sexual%20OR%20%22reproductive%20behavior%22%20OR%20mounting)|date=23 November 2006|publisher=Elsevier Health Sciences|isbn=978-1-4377-1300-8}}

==External links==
* {{Commons category-inline|Interspecies sex}}
* {{Commons category-inline|Mammal sex}}
* [https://web.archive.org/web/20040726025454/http://news.nationalgeographic.com/news/2004/07/0722_040722_gayanimal.html National Geographic]
* San Francisco Zoo has run [http://www.sfgate.com/bayarea/article/SAN-FRANCISCO-Not-your-mama-s-birds-and-bees-2522984.php a "sex tour" covering animal sexuality], on Valentine's Day
* [http://www.world-science.net/othernews/061024_gay-animals.htm A wild, and gay, kingdom] World Science
* [https://web.archive.org/web/20070927024509/http://www.gayprocon.org/bin/procon/procon.cgi?database=5-A-Subs-4.db&command=viewone&op=t&id=3&rnd=452.5414171644969 Is it relevant to look at the animal kingdom to determine if human same-sex behaviour is "natural"?]

{{Animal sexual behavior}}
{{Sex (biology)}}
{{Ethology}}
{{Zoophilia}}
{{Authority control}}

{{DEFAULTSORT:Animal Sexual Behaviour}}
[[Category:Animal sexuality| ]]
[[Category:Ethology]]
[[Category:Reproduction in animals]]
[[Category:Mating]]
[[Category:Articles containing video clips]]