A study published in Current Biology has brought to light a unique mating behavior in mammals, specifically observed in the serotine bat. Unlike other mammals, penetration is impossible due to the seven-times longer and wider male penises compared to female vaginas. Instead of using their genitals for penetration, male bats use their oversized penises to maintain contact with females during copulation.
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, where the penis becomes engorged so that it becomes stuck or perhaps they simply could not insert it. However, this type of copulation had not been described in mammals until now.”
Researchers observed 97 pairings between males and females at two different locations and analyzed images captured using cameras placed behind a grate that they could climb onto. They also noted that the female’s abdomen appeared moist after copulation, suggesting semen transfer. However, further studies are needed to confirm sperm transfer.
The study also characterized the morphology of serotine bat genitalia by measuring erect penises and performing necropsies on deceased specimens. The findings reveal that when erect, male serotine bats’ penises are about seven times longer and seven times wider than female vaginas of the same species. This research opens up new avenues for studying mating behavior and genitalia morphology in other bat species.