The secret sex lives of bats: Study reveals how males have penises 7 times longer than their partners’ vaginas – and use them as an ‘arm’ during romps that can last up to 12 HOURS

In humans, the erect penis has only one function, but elsewhere in the animal kingdom it serves a highly innovative purpose.

The male serotinous bat uses its massive penis as an “extra arm” to move part of the female’s anatomy out of the way, scientists say.

This allows them to engage in mating up to 12.7 hours before the male climax.

A bat’s penis is about seven times longer than its partner’s vagina, and has a “heart-shaped” head seven times wider than the vaginal opening, so traditional penetrative sex can be harmful to the female.

Very little is known about how bats have sex, although previous research has shown that some bat species emit a strange “perfume” to find a mate.

The new study was conducted by experts in the Department of Ecology and Evolution at the University of Lausanne in Switzerland.

They claim that it describes the first known example of non-penetrative sex in mammals.

Professor Nicola Vassil, first author of the study, said: “By chance, we noticed that these bats had disproportionately long penises, and we always wondered, ‘How does that work?’”

“We thought maybe it’s like in a dog where the penis swells up after penetration so they’re locked together, or alternatively maybe they can’t put it inside, but this kind of intercourse has not been reported in mammals yet.”

The researchers speculate that bats may have evolved their massive penises in order to push aside female bats’ tail membranes, which females may use to avoid sex.

Professor Fassel said: “Bats use their tail membranes to fly and catch insects, and female bats also use them to cover their lower parts and protect themselves from males.”

“But the males can then use this large penis to overcome the tail membrane and reach the vulva.”

The serotinus bat (Eptesicus serotinus) is found throughout Asia and Europe, including the southern half of the United Kingdom, according to the Woodland Trust.

This species lives in open woodlands, hedgerows, gardens and pastures, but when it hibernates in the winter, it can be found taking refuge in old buildings, such as abandoned chimneys and interior walls.

To learn more about the species’ secret sex life, researchers installed cameras in two sites – a church attic in the Netherlands and a bat rehabilitation center in Ukraine.

Experts were able to take close-up pictures of the bats’ reproductive organs during sex by placing cameras behind a net that the bats could climb on.

In total, the team analyzed video footage of 97 mating events, all of which revealed that the small mammals do not engage in penetrative sex.

The researchers did not observe penetration at any time during the recorded mating events, although what they did observe was instructive.

During mating, the male bat grabs his mate by biting her neck and moving her pelvis (and fully erect penis) in a “probing” manner.

Once in contact with the female’s vulva, the male remains still and holds his mate in a long embrace.

On average, these interactions lasted less than 53 minutes, but the longest event lasted 12.7 hours.

“During this time we observed numerous social calls, probably emanating from the female,” the study authors say.

After copulation, the abdomens of female bats appeared wet, indicating the presence of semen, but more research is needed to confirm sperm transfer.

Female bats appear to use this strategy to choose the right mate to raise their offspring, even after the deed is already done.

“We still don’t know the mechanism behind this,” Fassel says. Therefore, this post-mating choice is called “hidden female choice.”

“In terms of evolution, this is also very interesting because sexual selection has driven the evolution of amazing traits,” Vasil says. “He’s really crazy.”

Females have an unusually long cervix, which may help them select and store sperm, but more research may be needed.

“This study reveals a new population pattern in mammals and presents an interesting research model,” the team concluded.

“Indeed, further research should focus on the role that female pre- and post-copulatory choice as well as competition between males play in the evolution of this prolonged and specific mating behavior.”

The paper was published in Current biology.