1. Giraffes Scientists say that homosexual activity among giraffes is, in many cases, more common than heterosexual activity. Source.

2. Bulls & Rams Farmers often come across bulls and rams that simply refuse to mate with females. Source.

3. Mallards Mallards have rates of male-male sexual activity that are unusually high for birds, in some cases, as high as 19% of all pairs in a population. Source.

4. Pigeons Both male and female pigeons sometimes exhibit homosexual behavior. As well as sexual behavior same-sex pigeon pairs will build nests, and hens will lay (infertile) eggs and attempt to incubate them. Source.

5. African Lion Male lions pair-bond for a number of days and initiate homosexual activity with affectionate nuzzling and caressing, leading to mounting and thrusting. About 8% of mountings have been observed to occur with other males. Pairings between females are held to be fairly common in captivity but have not been observed in the wild. Source.

6. Albatross Albatrosses can live until they are 70 years old and it's said they make a lifelong commitment to one bird. They incubate their egg together for 65 days, taking turns to find food. According to biologist Lindsay Young, who used DNA analysis to genetically test the birds' gender, some of the female pairs have been together for up to 19 years. Source.

7. Bed Bugs Male bed bugs are sexually attracted to any newly fed individual and this results in homosexual mounting. Source.

8. King Penguins Research shows around a fifth of all king penguin couples kept in captivity are gay. Source.

9. Black Swans Almost a quarter of black swan families are parented by homosexual couples. Male couples sometimes mate with a female just to have a baby. Once she lays the egg, they chase her away, hatch the egg, and raise a family on their own. Source.

10. Chinstrap Penguins Roy and Silo, two male chinstrap penguins at New York's Central Park Zoo have been inseparable for six years now. They display classic pair-bonding behaviorentwining of necks, mutual preening, flipper flapping, and the rest. They also have sex, while ignoring potential female mates. Source.

11. Bonobo Studies suggest 75 percent of bonobo sex is nonreproductive and that nearly all bonobos are bisexual. Source.

12. Bottlenose Dolphins Male dolphin calves often form temporary sexual partnerships, which scientists believe help to establish lifelong bonds. Such sexual behavior has been documented only relatively recently. Source.

13. Western Gulls Studies have shown that 10 to 15 percent of female western gulls in some populations in the wild exhibit homosexual behavior. Source.

14. Grouphorn Sheep Groups of male bighorn sheep engage in genital licking and anal intercourse to the point of ejaculation. Source.

15. Elephants African and Asian males will engage in same-sex bonding and mounting. Such encounters are often associated with affectionate interactions, such as kissing, trunk intertwining, and placing trunks in each other's mouths. Source.

16. American Bison Courtship, mounting, and full anal penetration between bulls has been noted to occur among American Bison. Source.

17. Dragonflies Male homosexuality has been inferred in several species of dragonflies. Source.

18. Uganda Kob Female kob perform oral sex on each other and even stroke each other's vulvas with their forelegs. Source.

19. Grey Whales In "slip-and-slide" orgies, groups of male grey whales, one of the oldest species of mammals, roll in the ocean rubbing their bellies against each other so that their genitals are touching. Source.

20. Guianan-Cock-of-the-Rock 40% of male Guianan-Cock-of-the-Rocks engage in some form of homosexuality sexual activity.

21. Japanese Macaque Same-sex relations are frequent. Females will form "consortships" characterized by affectionate social and sexual activities. In some troops up to one quarter of the females form such bonds, which vary in duration from a few days to a few weeks. Often, strong and lasting friendships result from such pairings. Males also have same-sex relations, typically with multiple partners of the same age.

22. Walrus Until Male walruses reach sexual maturity at age four, they are most likely exclusively involved in same sex relationships. Source.

23. European Polecats European polecats were found to engage homosexually with non-sibling animals. Exclusive homosexuality with mounting and anal penetration in this solitary species serves no apparent adaptive function.

24. Vultures 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. The keepers provided the couple with an artificial egg, which the two parents took turns incubating; and 45 days later, the zoo replaced the egg with a baby vulture. The two male vultures raised the chick together. Source.