A study published in Current Biology has documented the first time that sex without penetration has been observed in a mammal, specifically in the serotine bat. The penises of bats are about seven times longer than the vaginas of their partners and have a head-heart shaped 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, from the University of Lausanne, Switzerland, and lead author of the study stated, “We think that perhaps it is like in the dog, in which 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 genitals during copulation using images from cameras placed behind a grate that they could climb onto. They analyzed a total of 97 pairings from the Dutch church and the Ukrainian center. They also observed that the female’s abdomen appeared moist after copulation, suggesting the presence of semen, but more studies are needed to confirm that sperm was transferred.
The researchers characterized the morphology of the genitalia of serotine bats by measuring the erect penises of live specimens and performing necropsies on those that died. When erect,
