When Eavesdropping Pays Off
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Grasslands are the most threatened ecosystem on the planet, which is a problem because they store a lot of carbon. One third of all carbon on land is found in grasslands. And Andy Boyce has spent a lot of time standing in them. Sometimes the grass is knee high. Sometimes it's only stubble level. The prairie looks a little bit different wherever you go, and it changes hugely season to season. Go to Montana in early June, and the prairie is loud and teeming with life.

There are several species of shorebirds flying around, singing, defending their territories. There are innumerable small, hidden species of songbirds. Andy studies birds, in particular, the long-billed curlew.

A curlew is a shorebird about the size of a chicken with a mottled brown coat and a long, thin beak that curves. And curlews build nests in the prairie. Now, Andy is an ecologist with the Great Plains Program at the Smithsonian's National Zoo and Conservation Biology Institute. And in 2020, he and then-intern Andrew Drelin were tasked with catching one of these birds. But...

We were really having this problem with this one individual curlew where we would get within 5, 10, 20 feet of her and, you know, she would flush off the nest before we had a chance to capture her.

Prairies are also home to prairie dogs. These burrowing ground squirrels that live in networks of burrows known as towns, which can stretch hundreds to thousands of acres. And when Andy and Andrew got close, the prairie dogs started calling. And I think I said, well, like, you know, guys, I kind of think these prairie dogs are giving us away.

And Andrew, who later became a grad student in the lab, wanted to find out. So Andy planted the seed of this idea, and it really got my, like, mad scientist energy up, and I decided to test this wild idea as part of my dissertation. ♪

So today on the show, why eavesdropping on prairie dogs is a legitimate survival strategy. Plus how Andy and Andrew mimicked a predator on the landscape. I took a taxidermy badger and I strapped it to a remote-controlled car and made what we lovingly call the badgerinator. I'm Emily Kwong and you're listening to Shortwave, the science podcast from NPR.

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Andy and Andrew, prairie dogs, in addition to being very adorable, they're ecologically really important. Prairie dogs are what's known as a keystone species. What is that? What role do they serve in the grasslands? Yeah, totally. So in general, when we say keystone species, we mean an animal, an organism that has a disproportionately large effect on an ecosystem relative to, let's say, its biomass.

Prairie dogs are food for a huge variety of species out on the prairie. Prairie dogs physically modify the environment in a ton of ways. So they build burrows that other species use. They graze vegetation to create this really short grass habitat that a lot of animals like to nest and forage in.

They can't stand to have any sort of like vertical structure in their colonies, probably because they like to have long sight lines. They don't like perching places for predators. And this habit they have of clipping woody vegetation on the landscape, you know, it's something that keeps grassland grassland. Like grasslands thrive with disturbance. They need it. Otherwise, they'll become forests or savannas. So let's dive into the study that you and your team worked on.

You all wanted to know if these long-billed curlews with nests near prairie dog towns were actually taking advantage of the calls of prairie dogs to be alerted to predators. Andrew, how did you go about studying that? Yeah, so the first step is to actually find a long-billed curlew nest, which takes hours of work sitting out on the prairie watching very closely to, you know,

track a female or a male until they change incubation duties at the nest because their nests are super well concealed. And so pretty much the only way to reliably find a curlew nest is to watch for that changing of the guard and see that switch happen. And then essentially, once we found that curlew nest,

We would then flag out a little race course for our badgerinator on wheels. And we would come back a couple days later after we gave the curlews a little bit of downtime. And we would do one of two things. We would either have a speaker completely silent, not playing anything, or we would have a speaker playing a recording of prairie dog alarm calls in response to the badger.

And the badgenator is a taxidermied badger that you strap to a remote control car to be a predator-like proxy to see if it would set off this chain of events, this prairie dog call alarm system. Exactly. And I'm literally like...

a football field away looking through a telescope while piloting the badgerinator. And so it actually took a decent amount of coordination to like pull it off. And we're hiding either behind a work truck or behind a camouflaged hunting blind, you know, just trying to be like as inconspicuous as possible. And we're like essentially comparing the difference in the curlew's anti-predator behavior and that hunkering down on the nest with

with and without the prairie dog alarm calls to see if it gives that early warning advantage. The thing about Long-billed curlews that made this whole study work is that they have two totally different ways of sitting on the nest when they're incubating. So if they are not perceiving any sort of threat, you know, they're sitting on the nest on the ground, they've got their head up, they're like looking around for stuff.

But when they're threatened or they perceive a predator on the landscape, they just totally pancake. So like their long head and bill pressed like totally down to the ground doing their like best impression of a cow pie basically. So – You mean a pile of –

of poop? Oh, yeah. Yeah, totally. Yeah. Go on, go on, go on. No, yeah, there's this long-standing hypothesis that they are basically like, they basically like mimic bison, piles of bison dung on the landscape. I love birds. Okay, go on. So anyway, like, because they have this binary behavior of basically either head up or head down, we can tell when they're perceiving a predator. What did you ultimately find in the data analysis?

Yeah, so I felt a huge wave of validation upon seeing the results. When the curlews could actually hear the prairie dog alarm calls, it made a three times difference in terms of the effectiveness of that behavior. So they hid when the badger was three times further away. Is this a matter of life and death for them? Definitely.

That's what we think. Absolutely. Because these badgers are opportunistic predators. They're out there cruising around just hoping to see something and smell something. Yeah. The reason that we think this is extra important for curlews in particular is because they typically only have one nest a breeding season. So literally all of their eggs, all four of them, are in one basket for the entire summer. And then if that nest gets eaten by a badger,

then they have to wait a whole nother year, go through a whole nother migration cycle before they can have another nest. All of it makes me wonder about the work that prairie dogs are doing then on grasslands, aside from being adorable. They are one of a few keystone species in this habitat, right?

Just to imagine it, I mean, if something were to happen to the prairie dogs, how would it impact the grasslands? Yeah, well, I have bad news. Like, things have been happening to prairie dogs. So we are right now sitting at about... Prairie dog populations are sitting at about 2% of what they were historically before sort of Euro-American expansion through the West. So they have been, you know, systematically persecuted through poisoning and shooting, right?

There's also this introduced disease called sylvatic plague, which has been introduced from Asia, which decimates prairie dog populations. So, you know, honestly, the system that we were working in is amazing and it allows us to uncover some of these ecological relationships with prairie dogs.

But it's really rare. Prairie dogs are gone from most of the grasslands that they used to occupy. And I think that's one of the reasons we feel working on them is really important because uncovering these amazing things that they're doing on these landscape that potentially benefit other species we want to conserve will hopefully motivate, you know, increased prairie dog conservation efforts going forward. Yeah.

Yeah. I mean, if prairie dog populations shrink, what's at stake for the grassland ecosystem, especially considering how much carbon is stored in grasslands? Yeah. We know that intact prairie holds way, way, way more or sequesters way, way, way more carbon than tilled agricultural land. So it's really important to keep grasslands grasslands safe.

And I think as a society, we view the center of country, the Great Plains, as the breadbasket, right? And we see these landscapes as almost entirely for production. And they are hugely economically valuable. But because of that, we don't have giant grassland national parks all over the country like we do in mountains or deserts or northeastern forests.

And in terms of the prairie dog conservation story, another important angle is how much work indigenous nations do in terms of conserving and restoring the prairie dog ecosystem. We worked on Fort Belknap Indian Reservation, which is home to the Ahni and Nakoda nations. And just being out there on that landscape, which cows were grazing on the prairie dog towns, I was just so impressed with all the work that they were doing with very little resources to preserve.

keep this ecosystem something close to what it formerly was. Andrew and I are like hardcore prairie dog stands and aficionados at this point, but there are other imperiled grassland species that rely completely on prairie dogs.

If we want to have black-footed ferrets in this world, we need to do prairie dog conservation. Birds, there's a tremendous amount of money and interest in bird conservation. If we want to continue to have mountain plovers on this landscape, horned larks, long-billed curlews, burrowing owls, all these species rely on prairie dogs. So we can't effectively separate bird conservation for those species with prairie dog conservation.

Andy Boyce and Andrew Drelin, thank you so much for coming on Shortwave. Absolutely. Anytime. Thank you so much for having us, Emily.

Short Wavers, you know what I'm going to ask. Please follow us on the NPR app or wherever you listen to podcasts. Your support truly helps the show. This episode was produced by Burleigh McCoy. It was edited by our showrunner, Rebecca Ramirez, and fact-checked by Tyler Jones. The audio engineer was Robert Rodriguez. Beth Donovan is our senior director, and Colin Campbell is our senior vice president of podcasting strategy. I'm Emily Kwong. Thank you for listening to Short Wave from NPR.

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