Homosexuality in animals
Animal sexual behavior takes many different forms; even within the same species, researchers have drawn parallels between this and homosexuality, bisexuality, intersexuality and transgender behavior in humans. The presence of same-sex sexual behavior was not 'officially' observed on a large scale until recent times, possibly due to observational bias caused by social attitudes to same-sex sexual behavior. It appears to be widespread amongst birds, mammals and the apes. Some researchers believe it to have its origin in male social organization and social dominance, similar to the dominance traits shown in prison sexuality.
Bonobo
The bonobo, which has a matriarchal society (unusual amongst apes), is a fully bisexual species -- both males and females engage in heterosexual and homosexual behavior, being noted for lesbianism in particular.
In early February 2004 the New York Times reported a male pair of chinstrap penguins in the Central Park Zoo in New York City were partnered and even successfully hatched a female chick from an egg.[1] Other gay penguins in New York have also been reported to be pairing off.[1]
In October 2003 a study [1] was released, stating, that homosexual behavior in sheep is related to a region in their brain (called "ovine sexually dimorphic nucleus" or oSDN). The scientists found: "The oSDN in rams that preferred females was significantly larger and contained more neurons than in male-oriented rams and ewes. In addition, the oSDN of the female-oriented rams expressed higher levels of aromatase, a substance that converts testosterone to estradiol so that the androgen hormone can facilitate typical male sexual behaviors. Aromatase expression was no different between male-oriented rams and ewes."
Birds
Homosexual black swans of Australia will form sexually active male-male mated pairs and steal nests or form temporary threesomes with females to obtain eggs (the female is driven away after she lays the eggs), more of their cygnets survive to adulthood than those of heterosexual pairs possibly due to their superior ability to defend large portions of land.Lizards
Whip-tailed lizard females have the ability to reproduce through parthenogenesis and as such males are rare and generally disdained (from a Darwinian standpoint the females are passing their full genetic code to all of their offspring and do not want it compromised by sexual reproduction), the females engage in sexual behavior to stimulate ovulation.Sheep
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