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Squawk and Milou Male chinstrap
penguins, one of several homosexual
pairs at the Central Park Zoo.

Homosexual behavior in animals

Homosexual behaviour is common in the animal kingdom, especially in species closer to humans on the evolutionary scale, such as the great apes. Georgetown University professor Janet Mann has specifically theorised that homosexuality, at least in dolphins, is an evolutionary advantage that minimises intraspecies aggression, especially among males.

* Male penguin couples have been documented to mate for life, build nests together, and to use a stone as a surrogate egg in nesting and brooding. In 2004, the Central Park Zoo in the United States replaced one male couple's stone with a fertile egg, which the couple then raised as their own offspring.[10] German and Japanese zoos have also reported homosexuality among their penguins. This phenomenon has also been reported at Kelly Tarlton's Aquarium in Auckland, New Zealand.
* Courtship, mounting, and full anal penetration between bulls is common among American Bison. The Mandan nation Okipa festival concludes with a ceremonial enactment of this behaviour, to "ensure the return of the buffalo in the coming season." [citation needed] Also, mounting of one female by another is common among cattle. (See also, Freemartin. Freemartins occur because of clearly causal hormonal factors at work during gestation.)
* Homosexuality in male sheep (found in 6-10% of rams) is associated with variations in cerebral mass distribution and chemical activity. A study reported in Endocrinology concluded that biological and physiological factors are in effect.[11] These findings are similar to human findings studied by Simon LeVay.

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