The orchard bat (Eptesicus serotine) is a mammal that has earned the nickname of “Nacho Vidal” for its disproportionately large penis. Despite being seven times longer and wider than the female vagina, this species that inhabits most of Europe and the Iberian Peninsula has no choice but to mate in a non-penetrative way.
An international team of researchers has discovered that bats use their large penis as an extra arm to push against the female’s tail membrane during mating. This behavior, which resembles the “cloacal kiss” of birds, is the first documented case of non-penetrative sex in a mammal.
The researchers, led by Nicolas Fasel from the University of Lausanne, made this discovery after observing bats with disproportionately long penises and wondering how they managed to copulate. They analyzed 97 mating acts from both Dutch church attics and Ukrainian rehabilitation centers and found that bats do not practice penetrative sex. Instead, they grasp their mates by the neck and move their pelvises in a probing fashion until they make contact with the female’s vulva. Then they stay still in a long embrace.
Female bats also have unusually long cervixes, which could help them select and store sperm. The team speculates that bats may have evolved their oversized penises to push away female tail webbing, which they can use to avoid sexual intercourse.
The researchers now plan to study bat mating behavior in more natural contexts and are also investigating penis morphology and mating behavior in other bat species. They are even working on developing a “bat porn box,” which will be an aquarium with cameras everywhere to observe bat mating behavior up close.