Bat Love
Because this is a family publication, we'll let the authors of "Fellatio by Fruit Bats Prolongs Copulation Time," a study published in 2009 in Public Library of Science One, explain their findings in scientific terms:
The short-nosed fruit bat Cynopterus sphinx exhibits resource defence polygyny and one sexually active male often roosts with groups of females in tents made from leaves. Female bats often lick their mate’s penis during dorsoventral copulation. The female lowers her head to lick the shaft or the base of the male’s penis but does not lick the glans penis which has already penetrated the vagina. Males never withdrew their penis when it was licked by the mating partner. A positive relationship exists between the length of time that the female licked the male’s penis during copulation and the duration of copulation. Furthermore, mating pairs spent significantly more time in copulation if the female licked her mate’s penis than if fellatio was absent. Males also show postcopulatory genital grooming after intromission.
As scientists are not supposed to leap to conclusions, the researchers wrote that "at present, we do not know why genital licking occurs.”
Images: 1) Fruit bats. (Rob/Flickr 2) Graph depicting the relationship between the duration of fellatio and copulation and fruit bats. (Tan et al./PLoS One)