Homosexual behavior in animals
[6][7][8] The motivations for and implications of these behaviors are often lensed through anthropocentric thinking; Bruce Bagemihl states that any hypothesis is "necessarily an account of human interpretations of these phenomena".
In humans, the term is used to describe individual sexual behaviors as well as long-term relationships, but in some usages connotes a gay or lesbian social identity.
Such behavior is often elicited and exaggerated by the researcher during experimentation through the destruction of a portion of brain tissue, or by exposing the animal to high levels of steroid hormones prenatally.
The earliest written mention of animal homosexuality appears to date back to 2,300 years ago, when Aristotle (384–322 BC) described copulation between pigeons, partridges and quails of the same sex.
[21][23] Academic research into the ubiquity of same-sex sexual behavior was not carried out on a large scale, possibly due to observer bias caused by social attitudes to same-sex sexual behavior,[13] innocent confusion, lack of interest, distaste, scientists fearing loss of their grants or even from a fear of "being ridiculed by their colleagues".
However, the benefit from performing homosexual behaviors (which cannot result in the production of offspring) is less obvious, and some scientists have called it a "Darwinian paradox" because it is non-reproductive.
Others firmly argue no evidence to support these claims exists when comparing animals of a specific species exhibiting homosexual behavior exclusively and those that do not.
Additionally, boosting the levels of sex hormones during an animal's pregnancy appears to increase the likelihood of it birthing a homosexual offspring.
The males spent time in each other's society, guarded the common territory, performed greeting ceremonies before each other, and (in the reproductive period) pre-marital rituals, and if one of the birds tried to sit on the other, an intense fight began.
[1][44] More of their cygnets survive to adulthood than those of different-sex pairs, possibly due to their superior ability to defend large portions of land.
The only copies that were made available privately to researchers had the English text partly written in Greek letters, to prevent this knowledge becoming more widely known.
[55][56] In Odense Zoo in Denmark, a pair of male king penguins adopted an egg that had been abandoned by a female, proceeding to incubate it and raise the chick.
The Bremerhaven Zoo in Germany attempted to encourage reproduction of endangered Humboldt penguins by importing females from Sweden and separating three male pairs, but this was unsuccessful.
[69] Sphen and Magic, two male gentoo penguins in Sea Life Sydney Aquarium, paired in 2018 and went on to raise two chicks, Lara (formerly Sphengic) and Clancy.
[73] Marama and Rocky, two female gentoo penguins at Sea Life London Aquarium, had an "incredibly strong bond" for five years prior to adopting a chick who was born in June 2019.
[76] In 1998, two male griffon vultures named Dashik and Yehuda, at the Jerusalem Biblical Zoo, engaged in "open and energetic sex" and built a nest.
Dashik became depressed, and was eventually moved to the zoological research garden at Tel Aviv University where he too set up a nest with a female vulture.
In addition to sexual behavior, same-sex pigeon pairs will build nests, and hens will lay (infertile) eggs and attempt to incubate them.
[9]: 339–348 In captivity, they have been observed to sometimes perform homosexual and heterosexual penetration of the blowhole, a hole homologous with the nostril of other mammals, making this the only known example of nasal sex in the animal kingdom.
The Mandan nation Okipa festival concludes with a ceremonial enactment of this behavior, to "ensure the return of the buffalo in the coming season".
[88] Janet Mann, Georgetown University professor of biology and psychology, argues that the strong personal behavior among male dolphin calves is about bond formation and benefits the species in an evolutionary context.
The encounters are analogous to heterosexual bouts, one male often extending his trunk along the other's back and pushing forward with his tusks to signify his intention to mount.
[98] Male lions pair-bond for a number of days and initiate homosexual activity with affectionate nuzzling and caressing, leading to mounting and thrusting.
In contrast to bonobos, same-sex sexual behaviors are less common in Kibale chimpanzees (Pan troglodytes schweinfurthii) and primarily occur between adult males.
Oral contact with genitals and behavior similar to male-female forced copulation between sexually mature sub-adult males were observed.
Among monkeys[clarification needed], Lionel Tiger and Robin Fox conducted a study on how Depo-Provera contraceptives lead to decreased male attraction to females.
[126] The family structure of the spotted hyena is matriarchal, and dominance relationships with strong sexual elements are routinely observed between related females.
[128][failed verification] Early writings such as Ovid's Metamorphoses and the Physiologus suggested that the hyena continually changed its sex and nature from male to female and back again.
Some parthenogenetic lizards that perform the courtship ritual have greater fertility than those kept in isolation due to an increase in hormones triggered by the sexual behaviors.
[137] Scharf et al. says: "Males are more frequently involved in same-sex sexual (SSS) behavior in the laboratory than in the field, and isolation, high density, and exposure to female pheromones increase its prevalence.
