Study reveals first known mammal to reproduce without penetration

Bats can be considered the strangest mammals. They are the only creatures among mammals capable of active flight, and researchers say they have discovered another unique feature.

A video reveals that the dusky peppermint bat may be the first known mammal to mate without penetration.

Also known by the scientific name Eptesicus serotinusdark peppermint bats mate by touching their genitals.

The male bat uses his penis like an arm to push away a protective membrane from the female’s vulva, according to a study published Monday in the journal Current Biology.

Bats have an “incredible” reproductive biology that has been difficult to study given the nocturnal and secretive nature of many species, said study co-author Nicolas Façal, a bat expert at the University of Lausanne in Switzerland.

“Most of the time you’ll see their back against the wall and you won’t see what’s really going on in front,” he said.

However, thanks to the efforts of a Dutch bat enthusiast who installed 18 video cameras in a church in the Netherlands that was home to a colony of dusky peppermint bats, Fasel and his colleagues were able to analyze 93 mating events in detail.

Video of four more mating events involving the same species came from collaborators at a bat rescue and rehabilitation center in Ukraine.

“You can actually see the copulation and see that the penis is not going in,” said Casol.

The images showed that half of the recorded mating episodes lasted less than 53 minutes, while on one occasion a pair of bats remained together in a copulative embrace for more than 12 hours.

The behavior is similar to “cloacal kissing”, a form of mating used by many birds.

WhatFasel and his colleagues observed in the videos could solve a long-standing puzzle about the reproductive biology of this bat species and others in the same family.

Incompatible genitalia

The male bat’s penis is about seven times longer than the female’s vagina and has a heart-shaped head that is seven times wider than the vaginal opening.

These are characteristics that seem to make penetrative sex difficult, if not impossible, Fazel noted.

Teri Orr, an assistant professor and expert on bat reproductive systems at New Mexico State University, said she was initially “surprised” to see that males may be using their genitalia as a “copulatory arm” and “perhaps transferring sperm in the same way.” what birds do.” ”

Orr is not involved in the study.

“Bats use their uropatagia (tail membranes) in many unique ways, like fishing nets, to capture young during birth and so on. So they are helpful in many ways, but perhaps a hindrance during mating,” Orr said.

“I agree that the male of this species can use his genitalia to navigate the female’s tail, but there are some important things to work out,” she added in an email. “On the one hand, how exactly is the sperm transferred, and on the other, what is the female doing in this pair?”

The dark peppermint bat’s behavior reported in the paper is “bizarre and unique,” ​​if true, said Alan Dixson, a biology professor at Victoria University of Wellington in New Zealand and author of the 2021 book “Mammal Sexuality: The act of mating and the evolution of reproduction”.

However, in his opinion, the researchers did not provide enough evidence to support their unusual claim, added Dixson, who was also not part of the study.

“Open question”

Study co-author Susanne Holtze, a senior scientist at the Leibniz Institute for Zoo and Wildlife Research in Berlin, acknowledged that they were not able to definitively prove the transfer of sperm from male to female bats and said this will be the focus of future research. .

“It is an open question how semen actually reaches the female reproductive tract. There may be some type of suction involved. We cannot fully answer this mechanism,” she said.

Holtze, an expert in assisted reproduction in animals, said the information discovered during the study would help in his work to find a way to artificially inseminate bats.

“There are more than 1,000 species of bats and many of them are also threatened with extinction,” she said. “Until now, no sufficient strategy for assisted reproduction has been established.”

Orr, a bat expert at New Mexico State University, said the study would inform his lab’s work on bat reproduction and whether unusual reproductive behavior has any implications for understanding human infertility.

“Bats do a lot of extreme things during reproduction, from storing sperm to prolonging the length of pregnancy,” she explained.

There are few bat biologists, and most tend to focus on the more obvious but still fascinating aspects of bat biology, such as flight and echolocation, “rather than what bats are doing ‘behind closed doors.’” , Orr said.