Top 10

Homosexual activity between male bisons is more common than heterosexual copulation. That's because female bisons only mate with bulls about once a year. During mating season, males that get the urge engage in same-sex activities several times a day. And so, more than 50 percent of mounting in young bison males happens among the same gender.

Among giraffes, there's more same-sex than opposite-sex activity. In fact, studies say gay sex accounts for more than 90 percent of all observed sexual activity in giraffes. And they don't just get straight to business. Male giraffes know how to flirt, first necking with each other - that is, gently rubbing their necks along the other's body. This foreplay can last for up to an hour

Both female and male bottlenose dolphins display homosexual behavior, including oral action where one dolphin stimulates the other with its snout. In the bottlenose world, homosexual activity occurs with about the same frequency as heterosexual play. Male bottlenose dolphins are generally bisexual - but they do go through periods of being exclusively homosexual.

Homosexuality is common among lions as well. Two to four males often form what is known as a coalition, where they work together to court female lions. They depend on each other to fend off other coalitions. To ensure loyalty, male lions strengthen their bonds by having sex with each other. Many researchers refer to this behavior as your classical 'bromance' rather than homosexual pairing.

Same-sex pairing is not just normal in the animal kingdom - it's even common. Studies suggest that about 1,500 animal species are known to practice same-sex coupling - from insects, to fish, birds and mammals.

Both female and male macaques engage in same-sex activity. But while males usually only do so for a night, females form intense bonds with each other and are usually monogamous. In some macaque populations, homosexual behavior among females is not only common, but the norm. When not mating, these females stay close together to sleep and groom, and defend each other from outside enemies.

The Layson albatross, which nests in Hawaii, is known for its large number of homosexual partnerships. Around 30 percent of pairings on the island of Oahu are made up of two females. They are monogamous, and usually stay together for life - as it takes two parents to successfully rear a chick together. The chicks are often fathered by males that are already in another committed relationship.

Bonobos are considered the closest living relative to us humans, and are known for seeking sexual pleasure. They copulate frequently, including with the same sex. They do so for pleasure - but also to bond with each other, climb the social ladder and reduce tension. About two-thirds of homosexual activities happen among females, but also males enjoy a roll in the grass with each other.

Like many birds, swans are monogamous and stick with one partner for years. Many of them choose a same-sex partner. In fact, around 20 percent of swan couples are homosexuals - and they often start families together. Sometimes, one swan in a male couple will mate with a female, and then drive her away once she's laid a clutch of eggs. In other cases, they adopt abandoned eggs.

Male walruses only reach sexual maturity at the age of 4. Until then, they are almost exclusively gay. Once they've reached maturity, most males are bisexual and mate with females during breeding season - while having sex with other males the rest of the year. It's not just gay sex though - the males also embrace each other and sleep close to one another in water.

Studies suggest that up to 8 percent of males in flocks of sheep prefer other males, even when fertile females are around. However, this only occurs among domestic sheep. Studies have found that these homosexual sheep have a different brain structure than their heterosexual counterparts, and release less sex hormones.