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As we approach the end of the year, the days are getting shorter and the nights longer.The team at Boise State Public Radio is leaning into the darkness to share stories that take place at nighttime and bring you to spaces that are bustling – or undisturbed – after the sun sets.Find the stories in our series “After Dark” below, or hear them on Morning Edition.

The important work of bats we don't see, and how researchers are working to understand how they communicate

Some of the most important pest control, pollination and seed dispersion work in the natural world happens at dusk and after dark - done by bats. Researchers are working to better understand and protect bats, including at Idaho’s Craters of the Moon National Monument and Preserve.

It starts by trying to understand what bats are ‘saying’ in frequency ranges beyond what human ears can hear.

“About 20 to 50 kilohertz is about the range that bats are operating in,” explained Mauro Hernandez, a bat researcher with Oregon State University working at Craters of the Moon.

Using special microphones, researchers can record bats' sonar emissions - the sounds used to navigate and ‘see’ what’s around them in near or total darkness.

“I use a special software, and it actually allows me to see the calls and the waveforms of these bat calls as they echolocate. So I'm able to see what they're seeing,” he said.

Echolocation pulses can change depending on how fast a bat is flying or what they’re looking for. ‘Feeding buzz,’ when a bat might be closing in on an insect for dinner, is a burst of rapid pulses also used when they are flying closer to an object like a cave with a tight entrance.

The sounds can be converted into the human hearing range, too. Some zoos and bat exhibits can monitor bats' echolocation calls in real time, Hernandez said.

“As the sun starts to set, you'll start hearing these sounds across the night,” he said. “We also use red lights. You can kind of see the bats swinging in and out of view. But it's really quite astounding, you know, since we don't really think about bats when we're out at night and then you put out these detectors and suddenly you get a picture of how busy the night air actually is.”

Around 14 different bat species call Idaho home and places like Boise were likely once prime roosts.

“Along the river that runs through the middle of the city was undoubtedly amazing bat habitat before people settled here,” Boise State University Professor of Biology Jesse Barber said. “Now, it's quite rare to see bats even along what appears to be a natural stream in the middle of a major city.”

Water, trees and vegetation supporting robust insect populations would have supported bats, too.

Hernandez says what we don’t know about bats greatly outweighs what we do, for example, how many hundreds of thousands of bats even live in the state. His work includes using infrared cameras to try to observe and count bats, and special nets when capturing a bat for study is necessary. But he tries to keep his distance.

“Stress is a big thing with bats,” he said. “So that's one part of the job that we do at night.”

And bats do give clues if they know folks are nearby, too.

“They start getting a little more animated and start making noise during the daytime,” Hernandez explains. “So they do make noises that we can hear; that's not echolocation, that's just vocalizing.”

And those vocalizations are a helpful indicator that you should back off, he said.

Hernandez says another reason to keep his distance is to limit the potential spread of a dangerous fungus discovered in 2006 which leads to what’s called white-nose syndrome. It dissolves bats' skin and wing membranes and thrives in cold temperatures.

“It disturbs bats when they're hibernating, causes them to wake at odd hours during hibernation using up their fat reserves, using up their water sources.

The fungus has been found in Minnetonka Cave in southeast Idaho, but white-nose syndrome isn’t widespread among bats in Idaho ... yet.

Wind energy is another threat; air pressure generated by spinning turbines can cause internal hemorrhaging. Cats contribute to bat depredation, too.

Bats dying off may not seem concerning, as they’re often blamed for spreading disease. Hernandez says their potential role in the COVID-19 pandemic has made bats even more hated.

“I try to remove that anger towards bats. Because it's very easy to sort of point the blame and then, you know, not care about them and not feel like we need to help conserve and protect them.”

Without bats, we humans would probably have lots more mosquito bites. And because bats are a main pollinator for the agave plant, tequila and mezcal would probably be more scarce. But most of that work happens after dark, and we don’t see it.

Hernandez, studying bats since his early college years, says we should be paying more attention.

“In the state of Idaho, our little brown bat is likely going to be listed federally as an endangered species. And now it looks like we have to step in, in a way to try and conserve and protect the species,” he said.

The U.S. Fish and Wildlife Service is evaluating potential endangered species protections for the little brown bat.

Troy Oppie is a reporter and local host of 'All Things Considered' for Boise State Public Radio News.

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