A few years ago, Nicolas Fasel, a biologist at the University of Lausanne in Switzerland, and his colleagues developed a fascination with the penises of serotine bats, a species found in forests and the attics of old buildings throughout Europe and Asia.
Serotine bats sport abnormally long penises with broad, heart-shaped heads. When erect, the members are approximately seven times longer than a woman’s vagina and their bulbous heads are seven times wider than a woman’s vaginal opening.
“We asked ourselves: How does that work? How can they use that to copulate? Dr. Fasel recalled.
What they discovered has overturned an assumption about mammalian reproduction, namely that procreation must always involve penetration.
in a studyIn a paper published Monday in the journal Current Biology, Dr. Fassel and his colleagues presented evidence that serotine bats mate without penetration, making them the first mammals known to do so. Scientists discovered that instead of using their penises to penetrate their mates, male bats use them to push their partner’s tail membrane out of the way so they can line up their openings and engage in contact mating, a similar behavior. the one found in birds and known as the “cloacal kiss.”
To learn how these bats overcome their significant difference in genital size, Dr. Fasel and his colleagues analyzed nearly 100 mating videos of serotine bats. The videos were provided by a bat rehabilitation center in Ukraine and a citizen scientist who filmed bats in the attic of a church in the Netherlands. The images revealed a mating strategy unlike any other used by mammals.
While the two bats hang upside down, the male climbs onto the female’s back and grabs her by the back of the neck. Once he has a firm grip, the male will use his erect penis to push the membrane of the female’s tail to the side and probe between her legs until he locates her vulva. The male then presses the heart-shaped head of his penis against the female’s vulva and holds it there until the act is over. While this process took less than an hour for most of the couples the researchers observed, one couple did it for nearly 13 hours.
“It’s a really strange reproductive strategy, but bats are strange and have a lot of strange reproductive strategies,” said Patty Brennan, a biologist at Mount Holyoke College in Massachusetts who studies the evolution of genital morphology but was not involved in the study. She points out that bats have evolved penises equipped with everything from hair to spines, so she wasn’t surprised that one species ended up with a penis too big to penetrate its mate.
While the serotine bat’s paddle-shaped penis may not be well suited for penetrative sex, its size and shape make it the perfect tool for moving the tail membrane of females. This flap of skin, which connects the bat’s tail to its legs, not only aids in flight but also offers females a means of covering their vulva, making it difficult for potential mates to gain access.
Dr. Fasel and his colleagues suspect that male serotine bats evolved their disproportionately large penises to avoid the female’s tail membrane as part of “a really interesting evolutionary arms race based on sociosexual conflict,” Dr. Fasel said. .
Like males of their species, female serotine bats also have unique genitalia. Their cervixes are unusually long, which probably helps them select and store sperm.
Dr. Fasel and his colleagues plan to study the mating habits of serotine bats, as well as those of other bat species, in more detail. He wouldn’t be surprised, he said, to find contact mating in other species of bats, or even in other mammals. “There are some doubts, but let’s keep an open mind,” he said.
Dr Brennan said: “I think there are probably a lot of strange morphologies and behaviors that we just don’t know anything about.” For too long, he said, this type of research “has not been considered a serious academic activity.” The findings of this article, he maintains, are proof that even the most scandalous fields of science are worthwhile.