The serotine bat (Eptesicus serotine), a mammal that has been observed to engage in non-penetrative sexual behavior, is the first time that such behavior has been documented in a mammal. The penises of bats are about seven times longer than their partners’ vaginas, and the head of the penis is seven times wider than the vaginal opening. Both the size and shape of the genitalia make penetration impossible, and it was discovered that instead of functioning as a penetration organ, they are used as an extra arm to move the female’s tail sheath away and maintain contact during mating.
This research was conducted by a team of scientists from various institutions, including the University of Lausanne in Switzerland and a bat rehabilitation center in Ukraine. They observed genitalia during copulation using images from cameras placed behind a grate that could be climbed onto, collaborating with researchers who had filmed pairs at a bat enthusiast’s home in the Netherlands and at a rehabilitation center in Ukraine.
The study revealed that these bats do not practice penetrative sex. Instead, they engage in cloacal kissing-like behavior during which males grasp their mates by the nape of their necks and tentatively move their pelvis until they come into contact with the female’s vulva before staying still and hugging them. On average, these interactions lasted less than 53 minutes but some lasted up to 12 hours.
The researchers also analyzed measurements taken from live specimens captured as part of other studies (serotines and vespers are conveniently known for having erections under anesthesia) and performed necropsies on those that died in rehabilitation centers to characterize morphology of genitalia.
This study is significant because it provides new insights into how bats mate, which has previously been unknown. It also raises questions about how this type of behavior might be adaptive for these animals. Further research will be needed to understand more about this unique form of sexual behavior among mammals.