By Lori Youmshajekian

Most mammals mate with penetrative intercourse, but a single peculiar bat species with an oversize, bulbous penis seems to sweep that assumption apart. New movie proof indicates that throughout copulation, the male serotine bat—Eptesicus serotinus—instead employs its penis like an arm to thrust absent the female’s tail membrane and presses the tip from the vulva, according to research posted in Existing Biology.

Although gathering sperm samples from bats numerous a long time back, University of Lausanne evolutionary biologist Nicolas Fasel observed dozens of bat erections and discovered that the species’ penis was “huge” and had an oddly shaped head. After erect, the male serotine bat’s penis is practically a quarter of the length of the animal’s full body—making it about seven moments lengthier and wider than the female’s vagina.

“The form is super odd the major of the penis is a little bit like this,” Fasel suggests, cupping his fingers together to show the significant, heart-shaped idea. He and his colleagues puzzled above how these types of a configuration would make penetration achievable.

Fasel could imagine of two probable explanations: either the penis enlargement occurs just after penetration, as it does in canine, or the bats engage in contact mating, akin to the so-called cloacal kiss in birds—an arrangement in which sperm transfers when the rear orifices, or cloacae, of male and woman birds arrive into speak to.

By probability, Jan Jeucken, an amateur bat fanatic and co-writer of the new paper, experienced been observing a team of serotine bats that gathered in the attic of a church in the Netherlands. He e-mailed Fasel some videos of the bats copulating following listening to about the researcher’s desire in bat reproduction. In the video clips, it was very clear there was no penetration.

Fasel and his colleagues noticed 93 instances of the bats copulating, typically in films shot by Jeucken. The footage displays males’ greedy women and then using their penis as a type of “copulatory arm” to sweep aside the females’ tail membrane, Fasel says. The scientists theorized that hairs on the idea of the penis aided to posture it in opposition to the vulva right before ejaculation. Fifty percent of the copulations finished in a lot less than an hour (despite the fact that a single lasted a lot more than 12 hrs). After copulation, the fur on the females’ stomach appeared moist, suggesting that semen was deposited.

Teri Orr, a physiological ecologist at New Mexico Condition College, who was not included in the review, claims she was pretty stunned when she to start with read the paper. “It was this sort of an abnormal variety of conduct that we really do not actually know takes place in mammals,” she states. The scientists experienced the benefit of studying a colony centered on the attic, permitting them “really select apart what’s going on with this species,” Orr says.

Bats this kind of as E. serotinus—which is typical throughout Europe and Asia—are presently recognized to have “unique and really peculiar” reproductive behaviors, compared with other mammals, Fasel suggests. Males and women of a lot of bat species can retail outlet sperm for months, and girls can hold off ovulation until finally right after they hibernate, in accordance to Orr.

The team did not swab the bats to affirm sperm transfer, but Fasel says he is assured that it occurred. “We could see that around the vulva, it was pretty moist,” he suggests. Orr suggests subsequent investigation need to pinpoint whether the sperm is staying deposited and notes that there could possibly also be the risk of delayed sperm implantation, in which a fertilized egg remains inactive in the uterus for a length of time prior to it implants in the uterine wall and begins to develop— a phenomenon observed in feminine roe deer.

Although the new acquiring comes from a smaller sample of 1 bat species, “I have no question that this is more prevalent,” Fasel states. The behavior most likely occurs among other bats whose women have a related tail membrane, Orr says. Further than the “gee-whiz” element, these findings expose essential gaps in researchers’ know-how about bat replica, she adds. “Bats are this kind of a badly understood group, and they are inclined to be vilified,” Orr suggests. “At the end of the day, if we don’t fully grasp their reproductive biology, we’re going to be definitely challenged when it arrives to conservation.”