Masturbation
Not only humans masturbate, animals do too. The following animals have been seen masturbating: dogs, several kinds of monkeys and apes, cows, horses, whales, bats, and sheep. Even birds and reptiles masturbate (turtles, for example). In this case, this does not only affect animals that were domesticated, and live in captivity, but also includes wild animals, of both sexes.