Short Wave - The genetic secret helping bats survive a deadly epidemic

Episode Date: October 5, 2026

We’re easing you into Halloween season with an episode about bats. There’s a silent serial killer decimating little brown bats as they hibernate. White nose syndrome has driven populations across the U.S. to almost the brink of extinction over the last decade. But recently, conservation biologist Giorgia Auteri and her team noticed several genetic mutations in the survivors. These mutations could explain how natural selection has shifted the existing population – and inform conservation efforts in the future.Interested in more animal science? Email us your question at [e-mail] public media with NPR+ and enjoy perks for over 25 podcasts like this one. This show’s perks include sponsor-free listening. Learn more at plus.npr.org. See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Hey, shortwavers. Okay, let's talk about bats. Part of me thinks they're cute. I mean, I love Batman. And part of me thinks they're scary. So at baseline, I'm conflicted about how to feel about them. That's how I entered a conversation with shortwave producer Hannah Chin, not long ago,

when they told me bats in the U.S. are in danger. And of course, when I learned that, that, I immediately thought WWBD, like, what would Batman do? What would Batman do? I think that he'd investigate. Yeah, I mean, he's the world's greatest detective. That's what he's known for. Well, today, Gina, you and I are the bat detectives.

Okay. And I'm going to start our detective journey by telling you about the bat walk I went on here in New York City. It started like pretty much any other nature walk. We all convened in the parking lot. Everyone seemed really excited. I met quite a few people there. Parker, Julie, Bella, Andy. I'm wearing this shirt that my best friend got me

with all these different kinds of bats on it. It says Little Brown Bats with a drawing of a cute little bat. It was bats galore. I noticed that you have a bat tattoo. I do. I just got it. It's a little stick and poke. Everyone was so thrilled about even the possibility of seeing a bat.

I do like bats. I've never done a walk like this. We were like, are we going to be the only ones here? And then everyone showed up. There's a lot of people. It seems really popular. And honestly, like, I don't think I've seen a bat that up close. I've seen them in the sky pretty far away and knowing it's a bat.

Yeah, there were maybe 20 of us wandering around the Ridgewood Reservoir. And our guide, Nick Comparato, gave us a little bit of bat background. So here in New York City, the most common bat I see. And the most common bat I get in my research is the eastern red bat. Big brown bat I also see quite a bit. Horry bat I get sometimes. not as much as I'd like to. Nick's a bat biologist and a PhD student at Rutgers University,

and they lead these summer bat walks. But, Gina, this is where the detective part comes in. Right, right, because along the way of making this episode, we learned one of the main things endangering bats around the country right now is a deadly illness called White Nose Syndrome. White Nose Syndrome is a disease affecting bats. It's caused by an introduced fungal pathogen that probably was human transported from Eurasia. This is Georgia Oterrey.

She's a conservation wildlife biologist, and she works for bat conservation international. She told us that the type of fungus that causes the disease really thrives in cool, humid environments. Like the bat cave, or I'm guessing real-life caves as well. Exactly, which a lot of bats hibernate in. And this fungus, it can grow on the cave walls or the ground, even on the bats themselves. Because when they're hibernating, their body becomes cool enough that the fungus can grow on them. and the fungus actually starts secreting things that break down their tissue of their body and starts kind of eating them alive while they're trying to conserve energy and hibernate.

It's just really brutal. Nick told me for a while, every time they've gone to a bat conference, there were scientists in tears just mourning the loss of all of these bats to this unstoppable virus. But Georgia and her colleagues realized that some bats are surviving. So we're talking to her for this episode. Today on the show, the deadly fungus that's decimating bat populations in the U.S. and how some bats are able to survive it. You're listening to Shortwave, the science podcast from NPR.

Okay, Georgia, so even though we might not see them, bats are everywhere, you know, in the U.S., they're in caves, they're in trees, you know, like inside the hollows. And they kind of span the whole country, but they're actually fewer and fewer bats out there because of this white-nose syndrome, right? Yeah, absolutely, especially out in the east and Midwest. So do researchers know how it got there? We don't really know for sure, but probably like someone was just in a cave or something over there, and then they came over and spores got into, you know, suitable habitat here, which was in underground caves and mines. And then this fungus started proliferating.

Right. So like it grows on the bats. It infects them during hibernation while they're sleep. right? Yeah, while they're trying to sleep, they basically end up waking up from hibernation when they should be sleeping and conserving energy. That's how this fungus ends up killing them. What exactly do bats die of when they're infected with white-node syndrome? Like, is it starvation, or is it because they're waking up more often, or is it just more complex than that? Yeah, I usually say that they're dying of secondary physiological complications associated with

waking up too much from hibernation, because it's a little bit of like, sometimes that could lead to death from starvation, sometimes it might lead to death from dehydration, just like waking up. But usually it seems to be mostly like a starvation thing. It can also kind of be like an autoimmune response. Like sometimes their immune system goes too crazy. Because they're trying to fight off this mold.

Yeah. And it's kind of like a syndrome that was observed in people with like fighting off HIV and AIDS where they have kind of a same thing. They have an autoimmune like a really, harmful autoimmune flare-up response. So there's evidence that some of them are experiencing that as well. That's terrifying. And so like which species of bat are these affecting the most?

These cave bats, I'm guessing. It mostly affects cave bats. And some of these cave hibernating bats, it doesn't affect as strongly. Like maybe because they're a little bit bigger or they just have a different hibernation pattern. But right now, there's 12 species that are affected. this disease, 12 species of bats. One of them, the little brown bat, was previously the most abundant species of bat in the eastern U.S., and so its numbers have just tanked. It's had over 90%

declines, often over 95% declines depending on the area. Yeah. But I'm glad you brought that up because I want to focus specifically on the little brown bat for the rest of this episode. And there's good news, right? Because some little brown bats survived. Why do we think that is? Like, can you tell me a little bit more about how that happened? Yeah, totally. So when white nose syndrome swept through, it killed most of the little brown bats, but a subset of them survived. And those survivors, it seems like, oftentimes were genetically better disposed to survive, like frequent waking up from hibernation because of the fungus. So maybe they had things like they were genetically predisposed to have higher fat reserves going into hibernation, or maybe they were genetically predisposed to wake up less

frequently. We're still fully understanding how that happened, but basically we had a big population with lots of genetic diversity. We killed off a bunch of them selectively. And now the remaining bats tend to have different versions of some genes compared to the ones that died. Right. So we have this genetic variation in this very diverse population of little brown bats. why are scientists interested in studying these surviving bats and their genes? Yeah, I mean, I think there's two reasons scientists are interested in studying these survivors. One is that from a theoretical standpoint, it's really cool to see evolution in action. It helps inform our basic understanding of science.

And it's like, oh, things actually get pretty complicated and tangled pretty quickly. And then the second reason, though, is that it's really helpful for informing conservation efforts. it's sort of helping us tailor the nature of our conservation to the ways in which the species themselves are adapting to white nose syndrome. And this is something you're researching, right? So, like, what is your research found with these bat survivors? Yeah, so the work that I'm working on now gone in a couple different directions. So one was to try to look at the physical characteristics of the survivors and look at how

those vary. And one of the things we did find is that, like, bats when they're getting ready to go into hibernation, if they have a certain adaptive gene, they tend to have a higher body mass index. This, of course, makes a lot of sense, right? Yeah, they have more reserves before they go to sleep. Yes, exactly. Okay. And so when you're hibernating, you're saving energy.

And every time you wake up from hibernation, it's extremely energetically costly. That's really only meant to wake up a few times during the winter in order to have enough fat to make it through. So it could be that waking up less often, like just staying asleep, and letting the fungus eat away at you is actually a better way to get through the winter than waking up. It could also be that maybe some bats are like good at waking up but falling asleep really quickly again. That way each time they wake up, it's less energetically costly. It makes me think of like the aughts and like, you know, turning on and off your computer took up so much energy that you like keep it on, you know? So it's like the waking up and falling asleep takes so much.

energy. I should say this is getting to kind of like another point, which is that, unfortunately, it's not like a one-to-one relationship with genes and their functions. Like, oftentimes we don't really know. Right. And also, even more critically, a lot of times one gene actually affects multiple different traits of a species. And so it makes it really tricky. Like, if you're a bat, you can't just optimize yourself for white nose syndrome without changing something else. A lot of times there's tradeoffs. I guess like the second prong right now of my current research is looking at whether bats are evolving to white nose syndrome in part via reproductive tradeoffs, tradeoffs in reproduction. Oh, okay. Interesting. So what do you mean by tradeoffs of reproduction?

I would think about it like this. Like let's say you are a female little brown bat. Little brown bats actually are pregnant. They become pregnant in spring. And then they migrate out of their caves while pregnant to their summer tree or wherever that they're going to have their beach house. Yeah, to their beach house. Let's say then that something goes wrong with the pregnancy or maybe, oh, just kidding, I'm not actually pregnant. Guess what? Instead of spending the spring and summer raising a baby and nursing that baby and taking care of it, she potentially has a lot more energy to spend just on herself and maybe recovering from white nose syndrome. She's having me time. Yeah, fall comes.

And she's much healthier possibly compared to the females. She has higher BMI, higher fat reserves. She's ready for hibernation. She's potentially much more likely to survive compared to those other female little brown bats. These bats have a really slow life history. So that means that they live a long time and they don't produce babies very often. But yeah, little brown bats, they typically just have one pup a year. and they'll live for up to 34 years in the wild as the record right now.

And like for context, like white nose syndrome was discovered in 2006. So like at ground zero where it was discovered, it won't be until like 2040 that the last little brown bat would hypothetically die that was born before white nose syndrome. So we potentially have a lot of well adapted adults flying around that aren't necessarily reproducing young at the rate we would like because it takes a lot of energy to survive the disease and it takes a lot of energy to raise a baby. Yeah, there's a tradeoff, right? You have survival at the cost of potentially not reproducing. Yeah, exactly. To kind of draw it full circle, like the gene that I found that is most associated with higher BMI, higher pre-hybernation

BMI in bats with white nose syndrome. That same gene in humans is associated with earlier onset of menopause and pregnancy disorders. Could we see this continuing decline or even a faster decline of the little brown bat population if the survivors are having babies at a slower rate? Yeah, I think we could see a continued decline just at a slower rate. We could see, you know, stabilization just at these newer, lower levels, or we could see increasing populations depending on, you know, what genes are under selection in that population. And indeed, we actually see all three of those things, depending on where we look in the U.S. So I think looking at the genetics really helps us understand what's going on in the broader picture.

Georgia, thank you so much for coming today and talking to us about bats. Yes, definitely. Thank you so much for having me. If you like this episode, share it with a friend. Maybe a friend that goes to cons and takes pictures with Batman. I did that. Or a friend that loves all those critters that some people find really scary. This episode was produced by Hannah Chin. It was edited by a showrunner Rebecca Ramirez and fact-checked by Tyler Jones.

The audio engineer was Anli Huang. I'm Regina Barber. Thank you for listening to Shortwave from NPR. See you next time.