AUDIE CORNISH, HOST:
Mountain lions can be scary. They certainly sound scary.
But a research project shows that much of our fear is based on mythology rather than scientific observation. Wyoming Public Radio's Melodie Edwards took a trek with a wildlife biologist who's aiming his video camera at mountain lions.
MELODIE EDWARDS, BYLINE: A heap of bones and grass lies along the bank of the Gros Ventre River near Jackson in western Wyoming. Researcher Mark Elbroch with the Panthera Puma Project says it's what remains of an elk calf.
MARK ELBROCH: And here you go. This is what it looks like. I tracked the whole attack.
EDWARDS: Elbroch tells the story with pride. He's known the mountain lion who made this kill - F61 - since she was a kitten.
ELBROCH: She came out of that thicket right there, took a calf elk right here and just dropped it - bam.
EDWARDS: Nearby, a camera bolted to a stake films anything that moves, even insects teeming on the carcass. But you can't just go out and buy one of these cameras. If you look inside, you'll find it's a mishmash of soldered-together parts.
ELBROCH: You know, I'd buy these expensive cameras and then be taking them apart, hacking them to try to get a motion detector to trigger them.
EDWARDS: In the 15 years Elbroch's been studying big cats, technology has improved. Now it's much lighter and more sensitive. Back at his office, we download images of F61 scraping grass over the carcass to hide it, just one of 100,000 videos he's collected, revealing a whole secret world.
What an amazing thing to be able to see inside...
ELBROCH: Oh, yeah.
EDWARDS: ...The den of a mountain lion.
ELBROCH: She just sat on a kitten.
ELBROCH: He's under 3 weeks old. There's a couple of noises where you'll hear the kittens but that little, kind of - it sounds like - imitating mountain lion purr - in the background. It's like a low noise that she kind of rumbles all the time.
And that's her.
EDWARDS: Is it purring?
ELBROCH: It's kind of a lower version than that, yeah.
EDWARDS: Elbroch says far from being the lone hunters of our nightmares, these are very social animals.
ELBROCH: You've got these huge male sons of mothers that are - have already outgrown their mothers, and the mothers are just rolling with them and licking them. They sleep in these huge, you know - cuddle puddles is what the interns like to call them.
EDWARDS: Elbroch says, sure, they might hiss and spit, but rarely do mountain lions hurt each other.
ELBROCH: So you're about to see one of the most violent interactions we ever recorded. Forty-seven just keeps coming in, even though 49 starts to actually physically attack her. And after this, they spent two and a half days sleeping next to each other. Ready?
ELBROCH: That is one of four instances we've ever seen physical contact, and it was minor.
EDWARDS: Elbroch says the most misunderstood sound is what he calls the infamous mountain lion scream.
(SOUNDBITE OF MOUNTAIN LION SCREAM)
ELBROCH: (Laughter) That's a female in heat.
EDWARDS: Not, as even many wildlife biologists have thought, the sound of an angry, hungry male about to attack. Elbroch says using motion-triggered remote cameras could help wildlife agencies manage mountain lions better in the future and allow them to remove individual problem cats instead of relying on open hunting seasons.
For NPR News, I'm Melodie Edwards in Jackson, Wyo.
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