Last January, one of Yellowstone's marked mountain lions went missing. Scientists traveled deep into the park to investigate. And that journey? It wasn't as straightforward as they thought it would be.

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Dan Stahler: Test Test 1-2-3…OK we are live

Narrator: This is Dan Stahler. And—I swear—Dan Stahler practically has fur in his blood. He studies wolves and elk…He’s the endangered species coordinator for Yellowstone National Park. And he’s the project lead for Yellowstone’s research on mountain lions—also called pumas or cougars—And last year, Dan and his team had a cougar mystery to solve.

Dan Stahler: All right, Good Morning. It’s January 28th. Dan Stahler, Colby Anton, Nathan Varley heading on in to the Black Canyon of the Yellowstone to go investigate on our only cougar collared right now, M198. He’s a 3-year-old male. We’re gonna go check it out and see what we see.

Narrator: First, a little background here on M198. The M stands for male and 198 is his identifying number. M198’s collar that Dan was talking about is very high tech. Dan Stahler: sort of FitBits if you will for cougars One of the things those collars can do is communicate with a satellite system to record the cat’s location on the landscape every 3 hours. Dan could log in on a computer, look at all those location points and see where M198 had been. Dan Stahler: We used those points to identify clusters on the landscape where he spent time. Then usually about a week after he was in that area we would go investigate. Narrator: Investigating the places where cougars have spent time turns out to be incredibly valuable. And it’s a little like a crime scene investigation that you see on TV. Dan and his team can comb the area for DNA, like hair and scat, to help identify individual cats … like how many are out there and who’s who. This non-invasive technique of getting at the demographics of a cougar population is a powerful tool for studying such secretive animals. Or, let’s say a cougar made a kill in that spot. And if so, was it a deer or an elk or a marmot… how old was the animal… was it healthy…how many animals did the cougar kill over a given period of time… these things tell scientists a lot about the food habits of cougars like M198 AND what their impacts might be on populations of prey species like deer or elk. Dan Stahler: We found where he’d killed an adult cow elk. It was the only animal he fed on for 20-some odd days. And that’s kinda typical of a male cougar. They can go a long time without feeding. They’ll make a kill, feed on it, then do their other cougar things and roam around. If the cat stops roaming around – if it stops moving altogether, then the collar sends Dan an alert. For M198, that alert meant that either the collar came off somehow, or it stopped moving because M198 was probably dead. And Dan and Colby and Nathan needed to figure that out. The problem was that the collar suddenly stopped transmitting GPS locations. So finding it was going to take a little work.

Dan Stahler: Colby, it’s too bad we don’t have a more recent track on him, Colby. He’s either down low or he’s tucked in a rock in the boulder field which let’s hope isn’t the case. Who knows Colby, we might get lucky. Narrator: Let’s just say that they didn’t get lucky. M198 had made his way into what Dan calls the Promontory. It’s a gnarly boulder field with rocks the size of cars. Dan Stahler: There are lots of places a kitty could tuck away up here. Narrator: This explains why Dan and his team were unable to get GPS coordinates from M198’s collar. There was no way a collar could communicate with the satellites in outer space through that huge pile of rocks. But those collars also come equipped with radio telemetry. And because the radio beacon transmits its signal directly to Dan’s handheld receiver, he could use THAT to zero in on M198. And the way that works: The closer Dan gets to the collar, the louder the blips -- the radio signal.

Dan Stahler: OK we’re getting closer guys.

Dan Stahler: It’s kind of a fun process because you try to read the signal but think about what the cat would do—how he would move through here. I don’t know they ARE cats. They do amazing things. It would be nothing for him to bounce through this boulder field, but you’d think he’d take a path that would be a little easier on him.

Dan Stahler: OK I think I see some blood up ahead. I don’t know for sure. Yeah….I see where birds or something pecked at blood in the snow.

Dan Stahler: Lot of tracks. He’s in there somewhere. Clicking in real nice on the telemetry now. It’s interesting. Something dramatic went on here. Because there’s blood all over the rocks…look at the stain on that lichen right there…there’s a bunch of cat hair stuck to the rock….

Dan Stahler: Wow. There’s caves all over the place in here….Wow. There’s blood way down. Holy smokes. Hey might be WAY down in here guys.

Dan Stahler: Uh this is a pretty…well…(grunting)…a little spelunking! I didn’t think I’d be doing THIS today.

Dan Stahler: Let’s hope he’s dead and not a wounded cat that’s not happy to see me.

Narrator: Twenty feet under the earth, tracking a bloody cat, Dan and Nathat started to piece together a story of what might have happened to M198.

Nathan Varley (talking to Dan): Did he get pinned in there by a bigger cat? Dan Stahler: Yeah bigger cat, maybe… Nathan Varley: …and they’re fighting…that’s nasty. Dan Stahler: That’s how toms die often. Nathan Varley: Lions are lions. They’re just so powerful Dan Stahler: And you know he’s a 3-year-old tom and was probably trying to establish himself in here and all it takes is one bigger tom to say nuh-uh. Dan Stahler: We’ll know. You know they crunch the skull… Nathan Varley: Oh wow. Brutal. Dan Stahler: …when they kill each other. I think we’ll see it in his head. Dan Stahler: Well, you know, he has an accelerometer collar. So we can look at the activity. We can look at the movements... We might even see signs of a chase taking place somewhere else once we get the data back from it. Nathan Varley: So like, ‘he ran over here and this is where the other cat caught up to him and pinned him in the rocks…” Dan Stahler: Mmmm Hmmmm Nathan Varley: That’d be pretty interesting, wouldn’t it? Dan Stahler: Yup Nathan Varley: That’d be really interesting…How ‘bout that? Dan Stahler: Yeah, like, what are the energetics of a cougar fight? Narrator: OK this is where the idea of the cougar FitBit really comes in. Scientists can use the information from accelerometer collars to understand a lot more about animal behavior and energetics – basically, how much energy it takes for an animal to live its life. This is pretty cutting edge stuff. Dan Stahler: So, our ability to study carnivores like cougars is changing all the time. We take advantage of new technologies that become available…And those of us who have iPhones or FitBits or any activity exercise monitoring machine, may have heard the term accelerometer because they’re all built to these devices. These collars have built in accelerometers that continuously measure the 3-D axis--the neck position--of the cat wearing the collar. So when the animal is walking or resting or pouncing on prey it will record a specific type of activity pattern This data has been calibrated with captive animals--captive cougars--wearing collars on a treadmill, jumping and pouncing on a training course … measuring how much oxygen they’re consuming and that translates to calories burned… Narrator: Calories in. Calories burned. This is the basis of energetics. Dan is collaborating with Colby Anton, a PhD candidate at UC Santa Cruz, on the energetics research. Dan says they will be able to link the data from the captive cougars to the wild cougars in Yellowstone. And biologists in the park have these same collars on wolves. Dan Stahler: …so we can compare the energetics of a stalking carnivore that lives mostly by itself – the cougar – compared to a group-living carnivore that chases after its prey – the wolf – and can see different patterns in their energetics that may have been shaped through evolution, might be shaped by current environmental conditions Narrator: Understanding how these animals respond to environmental conditions, how they survive…what they eat…where they go…how they affect each other and their prey… All of this goes beyond just understanding cougars or wolves. Dan Stahler: It’s really about understanding how the ecosystem works. I think those of us who work with these animals don’t think of ourselves as a wolf biologist or an elk biologist or a cougar biologist. We’re ecologists trying to understand the pieces that make this ecosystem function the way it does. Really, what we’re trying to do is understand Yellowstone—it’s importance to the world, its importance to science …to nature—through the lens of wolves and cougars and elk. So these collars have opened up that world in a much more accurate way. Narrator: And because they want to interfere with the lives of wild cougars as little as possible, Dan and Colby only fit a couple of cats with those collars. Which made M198’s even more important to get back.

Dan Stahler: OK, hey I’m gonna listen to the telemetry.

Dan Stahler: It’s 12:07 . Don’t tell me that beacon turned off.

Dan Stahler: That should not have shut off…(sighs) I don’t hear it Colby… Narrator: Despite continuing the search through the caverns without the signal, Dan and Colby and Nathan could not. Find. The cat. Dan Stahler: That pisses me off…. I hate leaving here without this cat and knowing the end of this story. ¬ Dan Stahler: Damn it, Colby . Colby Anton: beacon. Dan Stahler: Pffft…Another typical day in wildlife biology.

Narrator: I think most scientists will tell you that dealing with frustration and overcoming setbacks is something scientists get comfortable with pretty