Researchers have for the first time documented non-penetrative sex in a mammal, specifically in the serotine bat, according to a study published in Current Biology. The penises of bats are about seven times longer than their partner’s vaginas and have a head-shaped tip that is seven times wider than the vaginal opening, making penetration impossible. Instead of functioning as a penetration organ, male bats use their oversized penises to move the female’s tail sheath away and maintain contact mating.
Nicolas Fasel, lead author of the study from the University of Lausanne, Switzerland explained that “We think perhaps it is like in the dog, where the penis becomes engorged so that it becomes stuck or perhaps they simply could not insert it. But that type of copulation had not been described in mammals until now.”
The researchers observed genitalia during copulation using images from cameras placed behind a grate that they could climb onto. They analyzed 97 pairings from two different locations – Dutch church and Ukrainian center. Additionally, they studied female’s abdomen after copulation and found it to be moist suggesting semen transfer but further studies are required to confirm this.
The researchers also characterized the morphology of serotine bats’ genitalia by measuring erect penises of live specimens and performing necropsies on those that died. When erect, male serotine bats’ penises are about seven times longer and seven times wider than females’ vaginas of the same species. The researchers plan to conduct more research on mating behavior in other bat species and study penis morphology and bonding behavior in future studies.