The sun is starting to set over a gravel road next to a ranch south of Casper. The evening reflects purple in nearby puddles on the road. Project leader Katrina Cook, along with her field technician Becky Blankenship, is preparing for the first nocturnal call survey of the night, three-minute intervals where they stand in a single spot and just listens for frogs of any kind, in any direction.

The two scientists are tasked to find out if there are frogs here at all.

"It's valuable information because we still don't know where these guys all are and where they exist," Cook explains.

Frogs are all over Wyoming, but scientists know little about them - not where they live or what conditions they prefer. There are basic distribution models, but no in-depth map. There's so little information that most amphibians in Wyoming are considered a species of greater conservation need (SGCN). That means there's too little data to even gauge these frog's overall status. In 2017, there were nine amphibian species classified as SGCN including the western toad, wood frog and plains spadefoot. That last one is a frog we'll get to hear tonight.

So, the Bureau of Land Management, in partnership with the Wyoming Game and Fish Department and Wyoming's Natural Diversity Database, organized a two-season project to fill in some of the gaps in Wyoming's frog knowledge, and this summer is the first season. Cook is leading the on-the-ground effort collecting surveys around the state to make up that baseline data for Wyoming's frogs.

"Ideally, we would know how numbers are for each species. Where to find them, how to find them best," Cook explains, still standing on the deserted gravel road.

By the end of 2020, this information will be available to land managers to inform decision making.

All that starts with nights like tonight. Cook has already highlighted potential frog habitats around the state. They'll do surveys over two and a half months including in the southwest part of the state. Tonight, though, Blankenship and Cook will survey 10 miles of that habitat, stopping at 22 sites overall for three minutes each. Just before 9 p.m., it begins.

After three minutes of silence, both scientists get to the book-keeping. Cook and Blankenship fill out a form at each stop, writing down where they heard frogs, then use a compass to write down the direction and how many groups they heard. They also record temperature and humidity, vegetation, elevation, and barometric pressure. By the end, maybe all these data points will show a trend. For example, perhaps they will find there are more frogs in warmer and humid temperatures.

Auditory surveys like this one can only happen in the summer because it's mating season. Those croaks you hear are mating calls. But not all frogs croak.

"All dudes. It's a boy band," Cook says.

Auditory surveys are one method to track frog habitat and populations, along with visual surveys. But Cook and Blankenship also place acoustic monitors around the state to help track changes of habitat at any given site.

"Next stop?" Cook asks

"Next stop," Blankenship agrees.

"Good start," Cook says.

And so they repeat that three-minute interval every half mile. Before too long, it's completely dark out.

"Ooh, a shooting star! That was cool, it didn't have a tail," Blankenship says.

Cook doesn't drink coffee. But with the help of some sour candy, she says she's still feeling awake.

"Better than I thought I'd feel at 11 o'clock."

"It's already 11? It only feels like 10," Blankenship says.

With no more sunlight, the temperature has dropped, and it's completely quiet, with no highway noise or residential hubbub. Cook and Blankenship are now deep in the prairie. For this next interval, you can hear nothing but the near deafening sound of frogs.

Even after three minutes, Cook and Blankenship stand there for a second to enjoy the sound. Back in the car, Cook says she does appreciate the quiet of this work.

"I think being able to just be able to enjoy silence is nice, but you're also able to connect with nature in a way that not a lot of people get to. You're standing for three minutes and just focusing on what's around you auditorily," Cook said.

It's now well past 1 a.m. and cold. We've been out for over five hours, driven nine miles and done 21 surveys. The fatigue may finally be setting in.

"It gets to the point where, I know if I get tired enough, I get silly. Things get funny that normally wouldn't be," Cook says.

"Like a cow breathing heavily," Blankenship responds, and they both laugh.

They finish up the last three-minute interval, then it's back to the campsite.

Tonight's 22 surveys and all the data collected from them will be compiled into a final report after the summer of 2020. It will include a map so scientists can finally have a baseline of where all these species are, what kind of temperatures, vegetation, or relative humidity they like.

"The next study that gets added on to this one, [scientists] will be able to use this data to plan the next field seasons. It's kind of like we're a big team, helping each other out, taking steps along the way attacking different things," Cook said, as her truck rolls into the campsite.

Tonight, was one step towards collecting data that could have a big impact. At 2:30 a.m., it's been a productive day at work.