オーラルセックス
Oral sex has been observed in the animal kingdom among many species. It has been suggested that there is an evolutionary advantage due to the tendency of primates, non-primates and humans to have oral sex. Fellatio occurs with the fruit bat ("Cynopterus sphinx"); it has been observed when the bats are mating. These bat pairs spend more time copulating if the female licks the male than if she does not.