It's not actually common in the animal kingdom. It happens between animals, but it's not common. They don't have homophobia or gay pride parades either. Also this sums up the whole issue; most people think getting -blam!-ed in their butt isn't fun, so gays make attractive straight people uncomfortable because they think a gay being attracted to them means someone wants to pound their anus. Gays are people who are willing to put up with the pain of a butt -blam!- to be with someone they think is aesthetically pleasing. This is sad because beauty don't last. Finally there always have been, are, and can be genuine romantic friendships between guys; with and without sexuality.