in almost every animal species there have been observations of homosexuality. IN FACT there are entire SPECIES that are ENTIRELY female (meaning they're all lesbians.... ummmm.... lesbians... niiiiiiice). only people who are willfully ignorant can still say homosexuality is "unnatural." it so obviously isn't as it happens naturally everywhere with a pretty steady 10% chance of happening.
i think so far only insect's haven't had any observations of homosexuality.
http://www.sciencemag.org/c gi/content/abstract/135/349 9/212
apparently there are 6 species of lizard in that genus that are entirely female.
oh and i made a mistake earlier i didn't mean nearly ALL animals, i meant nearly all mammalian animals. so far homosexuality has been observed less frequently in fish, and lizards, though they still occur. aquatic mammals too have also been observed to have some who are born homosexual.
http://en.wikipedia.org/wik i/Homosexuality_in_animals
ranges from like 8% in rams to as high as 19% in some mallards.
http://en.wikipedia.org/wik i/Homosexuality
this one's for human homosexuality.