Male penguin couples in zoos in the UK, US and Germany have successfully hatched and reared "adopted" eggs. However, they have not necessarily stayed together - with some of the males later mating with female penguins
Laysan albatrosses, on the other hand, have been known to be lifelong homosexuals. On a Hawaiian island, where they are native, 31% of pairings were made up of two unrelated females. And after having sneak matings with males, they are known to raise chicks together
But experts suggest that, despite lots of animals engaging in homosexual behaviour, it does not mean any of them are inherently homosexual. It is arguably more accurate to call these species bisexual
Only two species have been observed showing a same-sex preference for life - one is humans, and the other is domestic sheep
