The penises of serotine bats are about seven times longer and seven times wider than the vaginas of females of the species
A team of researchers has discovered that a type of bat, the barn owl (Eptesicus serotinus), mates without penetration.
This is the first time sex without penetration has been documented in a mammal, they say in the study published in the journal Current Biology.
Bat penises are about seven times longer than female vaginas and have a "heart-shaped" head seven times wider than the vaginal opening.
Both the size and shape of the penises would make penetration impossible, and researchers have shown that rather than functioning as a penetration organ, bats use their oversized penises as an extra arm to pull the tail sheath away from the female and be able to maintain contact mating, a behavior that resembles the "cloacal kiss" of birds.
"By chance, we had noticed that these bats have disproportionately long penises, and we always wondered ' how does that work? '," explains Nicolas Fasel of the University of Lausanne in Switzerland:
"We thought that maybe it would be like in dogs, that the penis gets congested after penetration so they get stuck; or maybe they just couldn't get it in. But this type of copulation hadn't been described in mammals until now."
Cameras in a grid
Very little is known about how bats mate. For this research, Fasel has had the collaboration of a bat rehabilitation center in Ukraine , which filmed the genitals of mating couples thanks to cameras placed behind a grid to which animals could climb.
Also involved in the research was a bat enthusiast and amateur scientist, Jan Jeucker, who filmed hours and hours of footage of serotine bats in the attic of a church in the Netherlands .
In total, the team analyzed 97 pairings : 93 from the Dutch church and 4 from the Ukrainian bat rehabilitation center.
This is how they come into contact
In the recordings, the researchers did not observe penetration at any time and that the erectile tissues of the penis enlarged before coming into contact with the vulva .
During mating, male bats would grab their mates by the scruff of the neck and grope their pelvises until they made contact with the vulva, at which point they would stand still and embrace the females.
On average, these interactions lasted less than 53 minutes, but the longest lasted more than 12 hours .
After copulation, the researchers observed that the female bats' abdomens appeared moist , suggesting the presence of semen, but further research is needed to confirm that sperm was transferred during these alleged matings.
What are the genitals like?
The researchers also characterized the genital morphology of serotine bats by measuring both the erect penises of living bats and those of specimens that had died in bat rehabilitation centers.
Their measurements showed that, when erect, the penises of serotine bats are about seven times longer and seven times wider than female vaginas, and about one-fifth the length of bats.
Bats also have an unusually long cervix , which could help females select and store sperm.
Big penises to force females?
The researchers speculate that bats may have developed their large penises to separate the membranes from the females' tails , which they can use to avoid mating, Fasel explains:
"Bats use their tail membranes to fly and catch insects, and females also use them to cover their undersides and protect themselves from males, but the males can then use these large penises to get past the membrane the tail and reach the vulva."
The researchers now plan to study bat mating behavior in more natural contexts, and are also investigating penile morphology and mating behavior in other bat species .
"We're trying to develop a porn box for bats, which will be like a fish tank, with cameras everywhere," Fasel said.
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