In the world of animal reproduction, having a disproportionate penis is not always desirable. In fact, it can be quite the opposite for some species. The orchard bat (Eptesicus serotine), also known as the Nacho Vidal of the animal kingdom, has a truly unique reproductive system. His seven-times longer penis and heart-shaped head that is seven times wider than the vaginal opening make penetration after erection impossible.
But don’t worry, these bats have come up with an alternative way to mate: contact mating. That’s right, they use their large penises as an extra arm to push against the female’s tail membrane in a non-penetrative way, similar to birds’ cloacal kisses. This behavior has been observed for the first time in a mammal by an international team of researchers who analyzed 97 mating acts at a bat rehabilitation center in Ukraine and a church attic in the Netherlands.
The study was led by Nicolas Fasel from the University of Lausanne, Switzerland, and his team used cameras placed behind a grate that allowed them to observe every aspect of these mating acts. They found that bats do not practice penetrative sex, but instead use their enlarged penises to make contact with the female’s vulva during mating. On average, these interactions lasted less than 53 minutes, but one event lasted over 12 hours!
To better understand this strange behavior, the researchers also studied bat genitalia morphology by measuring erect penises and performing necropsies on specimens from various studies and rehabilitation centers. Their measurements showed that bats have penises that are about seven times longer and seven times wider than female vaginas when erect – which is quite large! The females also have unusually long cervixes that could help them select and store sperm during mating events.
The researchers now plan to investigate bat mating behavior further in natural contexts and study penis morphology and mating behavior in other bat species as well. They even plan on building “bat porn boxes” – aquariums with cameras everywhere – to observe their unique sexual practices more closely.