A study published in Current Biology has shed light on a previously unknown mating behavior in mammals – specifically, the serotine bat. Researchers have found that due to the seven-fold difference in size between their penises and vaginas, penetration is impossible. Instead, male bats use their enlarged penises to move the female’s tail sheath away and maintain contact mating.
Nicolas Fasel from the University of Lausanne, Switzerland, who led the study, stated that “this 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 a total of 97 pairings from the Dutch church and Ukrainian center. They also observed that the female’s abdomen appeared moist after copulation, suggesting the presence of semen. However, more studies are needed to confirm that sperm was transferred.
The morphology of the genitalia of serotine bats was also characterized by measuring erect penises of live specimens and performing necropsies on those that died. When erect, their penises are about seven times longer and seven times wider than their vaginas. Further research is needed to deepen our understanding of this unique mating behavior in other bat species and natural contexts.