"Vital signs," like blood pressure and pulse rate, are used in medicine to track human health. Paying attention to the little things can often help us better understand what's going on in the big picture. Scientists can monitor ecological "vital signs," too. In this episode, biologist Andrew Ray shows us that a little creature can tell us a lot about the Yellowstone ecosystem.

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TRANSCRIPT:

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FIELD SOUNDS FADING IN, CREW TALKING TO EACH OTHER ANDREW RAY: So you’re brand new so I'll just, lets. KACI FITZGIBBON: I do have one. ANDREW RAY: Oh you do have one? KACI FITZGIBBON: Yeah. ANDREW RAY: Okay well I'll take an extra, we'll have an extra. KACI FITZGIBBON: Okay. Awesome. ANDREW RAY: So you've used it before? FIELD SOUNDS FADING UNDER

SCOTT CHRISTY: I'm standing on the side of the Loop Road in Northern Yellowstone with biologist Andrew Ray and his intern Kaci Fitzgibbon Before we hike away from the road Andrew is explaining how to deploy bear spray in case we have a close encounter with a bear. He holds the eight-inch canister of pepper spray in one hand and puts his thumb on the plastic safety.

ANDREW RAY: But if somethings coming, we're all gonna sort of stand abreast, we're gonna face it, we're gonna talk to it, but we're gonna have this at the ready and part of having this at the ready is having your safety off. 'cause otherwise you're just pushing down on the safety. KACI FITZGIBBON: Yeah. ANDREW RAY: Sound good. KACI FITZGIBBON: Yeah.

SCOTT CHRISTY: Andrew spreads out a map across the tailgate of his truck and points to a spot in the mountains above us. ANDREW RAY: So just to give you guys a quick orientation. So we're here on loop road and you know big Blacktail Ponds. Anyway we're over here, we're gonna hike up and our goal is to hit site number two, there. ANDREW RAY: So it's a nice little pond sitting on the top of the hill—fantastic views. And it's a great spot for of chorus frogs and tiger salamanders.

SCOTT CHRISTY: Andrew is a biologist with the National Park Service’s Inventory and Monitoring Division.

ANDREW RAY: Yeah, I get to spend my summer knee-deep in these habitats that most people don't take time to wade into. And I get to explore them.

SCOTT CHRISTY: It’s May and snow is still melting off the higher elevations in the park. Hiking up the hill far above the road we bump into seven or eight elk moving off into the trees. We start talking about how the haunting sounds of elk bugling in the fall are one of the signature sounds of the Rocky Mountains.

ANDREW RAY: Yeah, so just as much of that leaves an impression that rich, real, authentic sound of wildlife, that's what chorus frogs are. That's the sound of a marsh. If marshes make sound, that's the sound of a marsh.

SCOTT CHRISTY: And Andrew says we’ll know the frogs when we hear them. They sing, sometimes a few at a time and sometimes a full chorus of many frogs. Moving over the hill, we see a small pond below us. There’s a wet grassy area leading into it. We think we hear a few chorus frogs, but they quiet down as we approach.

ANDREW RAY: Yeah, but that's the really cool thing about frogs is once you sit there and you sit still, they'll resume what they were doing. They'll suspend calling for a little bit and go into that cover, duck and cover mode but once you sit there and they realize you're not a threat, they'll resume what they're doing so they'll go right back to calling.

SCOTT CHRISTY: We sit quietly for a few minutes, and then, one by one, they start singing again.

ANDREW RAY: It's pretty fun to try to break it down. It sounded like two individuals are down there for a while then a third chimed and there was at least one here. And they're actually really rapid calls so it's just a second or two and it's like you're running your thumb down the tines of a comb—that sound, right? And then they'll do maybe 20 of those, or 25 of those in a minute, so they're really blasting it out advertising where they are. You now hear one over there.

SCOTT CHRISTY: Okay yeah, so what are they doing right now?

ANDREW RAY: They're advertising their presence. They're ultimately trying to attract a mate, but they're letting other males know they're present, that they've got the spot of the pond and then they're letting a female know where they are. They're so small, the vocalizations can help bring in the female.

SCOTT CHRISTY: Sometimes, the frogs will chorus from April all the way into July. And when they really get going, the sound can be intense… like this…

CHORUS FROG RECORDING FROM ARCHIVES

SCOTT CHRISTY: But Andrew says their full sound isn’t even the most unusual part about chorus frogs. Later in the year as late fall comes to Yellowstone…

ANDREW RAY: They are looking for a place to go hibernate. ANDREW RAY: And then you start to see... well, we can't see it obviously, but people who have measured it have started to see changes in their blood chemistry. ANDREW RAY: Essentially, they're creating an antifreeze.

SCOTT CHRISTY: Yep, he said anti-freeze. It’s a pretty amazing adaptation allowing them to survive winter in Yellowstone. A winter that can last up to six months. The chorus frogs make their version of ‘anti-freeze’ by producing extra glucose in their blood.

ANDREW RAY: What happens is, upwards of two thirds of their body is frozen. Completely frozen with a heart that has stopped, altogether, limbs that don't move, and lungs that don't function.

SCOTT CHRISTY: And the glucose in their blood protects their cells from collapsing while frozen.

ANDREW RAY: They're in that state as long as it's snowy.

ANDREW RAY: But it's absolutely remarkable to me that they over winter just inches below the surface.

SCOTT CHRISTY: And as crazy as that is, freezing just below the surface turns out to have a big benefit as winter comes to a close.

ANDREW RAY: When temperatures start to warm in the spring, the exact opposite happens, right? You start to get a little bit of heart and lung function. And, eventually, their extremities start to move. And the cool part about that is, when you're really close to the surface, and you get some warm, early, warm spring days, you're the first to respond. If the other species of amphibians are a meter down below the frost line, and deep into burrows, the temperatures aren't changing as rapidly as they are at the surface. So, these frogs are the first to get into ponds, as soon as the ice and snow is off the surface. And, so they're in the ponds earliest, because they are the closest to the surface.

SCOTT CHRISTY: This gives the chorus frogs a potential advantage over other amphibians and more time to take advantage of seasonal wetlands that may dry up later in the summer.

MUSIC TRANSITION

SCOTT CHRISTY: Yellowstone is home to four other species of amphibians including western tiger salamanders, Columbia spotted frogs, western toads, and plains spadefoot toads. There is one kind of environment they all need – shallow-water habitats. Biologists are concerned about how much of this habitat will be available in the future. As temperatures in the earth’s climate rise, these shallow-water habitats could dry up.

ANDREW RAY: One of the consequences of a warmer climate is less snow and less water to fill places like this. So the sounds that we hear, that are unique to this place, and the organisms that are present in these habitats, they don't have the ability to escape that. They don't have the ability to move away from that. There will most certainly be water and snow in Yellowstone long into the future. But a river with fish or a deep lake with fish is very different than this place that's before us. And so I guess the thing I want people to think about is there are biodiversity and physical consequences to a warming temperature. And these special habitats that are so biologically rich, they're the most threatened by a changing climate.

SCOTT CHRISTY: In one warm, dry year during the monitoring study, the shallow-water habitat shrunk by 40%. This led to a 50% reduction in breeding pairs of Boreal chorus frogs. Andrew thinks it’s likely we’ll see more of that in the future. And the potential for shrinking amphibian habitat isn’t just in Yellowstone.

ANDREW RAY: I mean, these are a group of organisms that were here before dinosaurs were here. So they're going to be here probably after humans are gone. But I think we can expect a future that has fewer amphibian species than were here, historically. And when I say here, I don't necessarily mean Yellowstone, but I mean on earth. And there are places where there really is a crisis, where amphibians are blinking out.

SCOTT CHRISTY: Andrew says the Northern Leopard frog, which used to be present just south of Yellowstone in Grand Teton National Park, hasn’t been seen in decades. Understanding what is going on with the remaining amphibians in Yellowstone depends on the data Andrew and others are collecting.

ANDREW RAY: So we study 31 watersheds around Yellowstone and Grand Teton, spread all around the park or all around both parks. And they represent just, what, one percent? I think there's 3,370 watersheds and we study just 31 of them. But we revisit those watersheds every year and we survey all of the ponds in those watersheds and it’s our hope that in one decade or in two decades we’ll have a data set that really does allow us to talk about long term change.

ANDREW RAY: So, while a warm year now may be followed by a cool, wet year, our future in this place looks drier. Which I think our data suggests means fewer ponds that support breeding chorus frogs, but also fewer ponds that support breeding Columbia spotted frogs, tiger salamanders, and western toads. While those are our vital signs, there's lots of other wetland dependent species. Beavers, trumpeter swans, moose, bats. Some bats are specialists to wetlands. If you have fewer wetlands on the landscape, you have fewer opportunities for those individuals to access water. While we're studying frogs, we like to remind people that they serve as just a proxy for other species that are dependent on wetlands. SCOTT CHRISTY: We are standing near the small pond when the weather starts to shift. Darker clouds move in off the horizon and Andrew, Casey, and I decide to pack up and head back toward the trucks. As we’re getting ready to go I asked Andrew why they chose boreal chorus frogs to monitor in the first place.

ANDREW RAY: We know that amphibians don't occupy every wetland in Yellowstone. We'd be naïve to think that they do. But we know species like boreal chorus frogs, from our monitoring, they occur in a third of the wetland habitats throughout Yellowstone and Grand Teton. That's high elevation, that's low elevation, that's near a river, that's far away from a river, they can use shallow, isolated habitats. And using something that's common and widespread is valuable. If those things become imperiled, the things that we know historically were common, then that should give us pause. That should make us think about what might be driving that change.

SCOTT CHRISTY: Biologists view amphibians as a kind of litmus test for big-picture changes in the environment – and the overall health of the environment. But Andrew thinks amphibians have value beyond being a vital sign for the park.

ANDREW RAY: I think it's relatable because a lot of us have had experiences with amphibians and we can still have those today. ANDREW RAY: But amphibians, like so many organisms, are experiencing declines. It's an opportunity to discuss our impacts, societal impacts on biology, but it's also a place to talk about discovery and to talk about biodiversity and to talk about climate change and to talk about the value of parks and protected places. CHORUS FROG SOUNDS SLOWLY FADING IN MUSIC FADING UNDER

ANDREW RAY: So to me, why do we care, because Yellowstone is a place that's still intact. And in terms of the lower 48, it's a really special place because it has its full complement of species. So it's important that we look not only at grizzly bears and wolves and bison, but it's important that we also look at frogs and fish and micro-organisms. ANDREW RAY: The most basic and fundamental part is that it is a part of Yellowstone’s biodiversity.

CHORUS FROGS MUSIC

SCOTT CHRISTY: For Yellowstone National Park, I’m Scott Christy. MUSIC FADING OUT CHORUS FROGS OUTRO