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A face mask can provoke the sexual appeal of a wrinkled-faced bat

For tips on flirting using a mask, take notes from nature experts: male bats with wrinkled faces. The first video of a wrinkled-faced sexual encounter shows a male covering his face with a mask flap while cutting and then, at a strategic moment, dropping the mask.

Even the basics of how bats mate (whether a male shares territory and advertises or females only buy from a multitude of shows) remain a mystery in more than 90 percent of the world's 1,400 species of bats, says the mammologist Bernal Rodríguez-Herrera of the University of Costa Rica in San José. It was a stroke of luck when a tip from nature guides in 2018 led him to the first scientific observations on courtship in one of the most elusive bats in the tropics of the Western Hemisphere, the wrinkled-faced bat, Centurio senex.

Males, but not females, grow loose loose with mostly white skin below the chin that look like a leggings pulled around the neck. A male can use skinny thumbs to pull the skin flap over his chin and mouth.

For the first time, investigators made a video about the mysterious masking of a masked young man from a wrinkled-faced bat (Centurio senex). With his natural white skin mask in the cover-up position, a male hangs in a Costa Rican jungle, ultrasonically drawing female attention. When a female rushes in, she drops the mask before they mate and then uses her thumbs to pull the skin flap over her chin and mouth once the female has advanced. It’s still a puzzle: what about the mask that helps cut a male?

It doesn’t seem likely that only males need cold chin covers. Unique sex excesses often serve to show off, like peacock feathers shot down in competition for female favor (SN: 16/06/15). Now, a lucky first look at the wrinkled-faced courtship suggests that the masks somehow play into a cutting competition, Rodriguez-Herrera and colleagues denounce on Nov. 11 in PLOS ONE.

For weeks, investigators watched as the bats gathered in the woods from six in the afternoon. until midnight, hung upside down at specific points with the masks on. Other bats occasionally beat briefly, but investigators did not know why.

It turned out that the hanging males were singing. Human hearing captures many nocturnal tropical sounds, such as the calls of frogs and owls, but not bats. However, bat recording instruments revealed a great song of ultrasonic bats. Sounds plunged into the range of human hearing only when an overflighted visitor made a rapid intrusion. Males also “move the tips of their wings constantly,” he says. He may not know if the screaming sound makes any sound, but "we think it's part of the courtship display."

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Watching males gather in a specific place to sing suggests to Rodríguez-Herrera that the wrinkled nose species adopts a mating bar approach, hitherto rarely reported among bats. Better known scientifically as lekking, males are grouped and displayed while females look for a gene contributor for the next generation. No help is offered to raise the resulting offspring.

For weeks, these male bats in Costa Rica spent the night rubbing their wings and singing backwards. The pale mask may function as a visual lure in low light or may play a role in the floating aromas, a romantic feature in some courtships of other bats. Or maybe the flap “helps sound the resonance,” Rodriguez-Herrera reflects. "We don't know."

What the researchers finally saw was a wrinkled nose pairing. A female landed on the perch of a male. The two clashed briefly. And as he repositioned himself for intimate contact, the mask fell off.

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