Homosexuality in animals

Homosexual behavior in animals refers to the documented evidence of homosexual, bisexual and transgender behavior in animals. Such behaviors include sex, courtship, affection, pair bonding, and parenting. A 1999 review by researcher Bruce Bagemihl shows that homosexual behavior has been observed in close to 1500 species, ranging from primates to gut worms, and is well documented for 500 of them. Animal sexual behavior takes many different forms, even within the same species. The motivations for and implications of these behaviors have yet to be fully understood, since most species have yet to be fully studied. According to Bagemihl, "the animal kingdom [does] it with much greater sexual diversity — including homosexual, bisexual and nonreproductive sex — than the scientific community and society at large have previously been willing to accept." Current research indicates that various forms of same-sex sexual behavior are found throughout the animal kingdom. A new review made in 2009 of existing research showed that same-sex behavior is a nearly universal phenomenon in the animal kingdom, common across species. Homosexuality is best known from social species.

The frequent observation of homosexual behavior in animals has been seen as an argument for the acceptance of homosexuality in humans as natural, however, this conclusion is controversial due to opposition to the LGBT social movements  and many experts in the field are reluctant to extrapolate from animals to humans. Some consider it also counters the 'peccatum contra naturam' ('sin against nature') — after Thomas Aquinas — established since the Medieval Christianities. Whether this has logical or ethical implications is also a source of debate, with some arguing that it is illogical to use animal behavior to justify what is or is not moral (see appeal to nature).

Applying the term "homosexual" to animals
The term homosexual was coined by Karl-Maria Kertbeny in 1868 to describe same-sex sexual attraction and sexual behavior in humans. Its use in animal studies has been controversial for two main reasons: animal sexuality and motivating factors have been and remain poorly understood, and the term has strong cultural implications in western society that are irrelevant for species other than humans. Thus homosexual behavior has been given a number of terms over the years. When describing animals, the term "homosexual" is preferred over "gay", "lesbian" and other terms currently in use, as these are seen as even more bound to the human condition.

Animal preference and motivation is always inferred from behavior. In wild animals, researchers will as a rule not be able to map the entire life of an individual, and must infer from frequency of single observations of behavior. The correct usage of the term homosexual is that an animal exhibits homosexual behavior or even same-sex sexual behaviour; however, this article conforms to the usage by modern research applying the term homosexuality to all sexual behavior (copulation, genital stimulation, mating games and sexual display behavior) between animals of the same sex. In most instances, it is presumed that the homosexual behavior is but part of the animal's overall sexual behavioral repertoire, making the animal "bisexual" rather than "homosexual" as the terms are commonly understood in humans, but cases of clear homosexual preference and exclusive homosexual pairs are known (see examples for details).

Research on homosexual behavior in animals
The presence of same-sex sexual behavior was not 'officially' observed on a large scale until recent times, possibly due to observer bias caused by social attitudes to same-sex sexual behavior, innocent confusion, or even from a fear of "being ridiculed by their colleagues." Georgetown University biologist Janet Mann states "Scientists who study the topic are often accused of trying to forward an agenda, and their work can come under greater scrutiny than that of their colleagues who study other topics." They also noted "Not every sexual act has a reproductive function ... that's true of humans and non-humans." It appears to be widespread amongst social birds and mammals, particularly the sea mammals and the primates, as well as bugs such as Adam Friedland. The true extent of homosexuality in animals is not known. While studies have demonstrated homosexual behavior in a number of species, Petter Bøckman, the scientific advisor of the exhibition Against Nature? in 2007, speculated that the true extent of the phenomenon may be much larger than then recognized:

No species has been found in which homosexual behaviour has not been shown to exist, with the exception of species that never have sex at all, such as sea urchins and aphis. Moreover, a part of the animal kingdom is hermaphroditic, truly bisexual. For them, homosexuality is not an issue.

An example of overlooking homosexual behavior is noted by Bruce Bagemihl describing mating giraffes where nine out of ten pairings occur between males.

"Every male that sniffed a female was reported as sex, while anal intercourse with orgasm between males was only 'revolving around' dominance, competition or greetings." Some researchers believe this behavior to have its origin in male social organization and social dominance, similar to the dominance traits shown in prison sexuality. Others, particularly Joan Roughgarden, Bruce Bagemihl, Thierry Lodé and Paul Vasey suggest the social function of sex (both homosexual and heterosexual) is not necessarily connected to dominance, but serves to strengthen alliances and social ties within a flock. Others have argued that social organization theory is inadequate because it cannot account for some homosexual behaviors, for example, penguin species where same-sex individuals mate for life and refuse to pair with females when given the chance. While reports on many such mating scenarios are still only anecdotal, a growing body of scientific work confirms that permanent homosexuality occurs not only in species with permanent pair bonds, but also in non-monogamous species like sheep.

One report on sheep cited below states:

Approximately 8% of rams exhibit sexual preferences [that is, even when given a choice] for male partners (male-oriented rams) in contrast to most rams, which prefer female partners (female-oriented rams). We identified a cell group within the medial preoptic area/anterior hypothalamus of age-matched adult sheep that was significantly larger in adult rams than in ewes...

In fact, apparent homosexual individuals are known from all of the traditional domestic species, from sheep, cattle and horses to cats, dogs and budgerigars.