I have to disagree with you a little there Stephanie.
There is a flock of penguins in a zoo (Belgium or Holland or someplace around there) where a number of the males have formed bonds that mimic the pairing bonds that a male and female penguin will make when choosing a reproductive mate. Even when separated and put with females, they show no interest in the females and then get back together with the same sex partner when reintroduced.
A study was done on sheep a number of years ago where a group of observers watched a flock of sheep and wrote down which animals mated with which animals and so on. When the brains of these sheep were dissected, there were physiological differences between the brains of the rams who mated with rams and the brains of the rams who mated with ewes.
Recently it has been found (read an article in a science journal on it) that in humans, homosexuality is likely to be caused to the fetus' exposure to certain hormones at specific times during gestation.
BACK TO THE TOPIC!
Male snakes will mate with other male snakes as a sign of dominance but obviously, female snakes have to hemipenes, so whilst they can physically dominate another snake by crawling all over them, they have nothing to insert!