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Yellowstone Cougar Project providing insight to lions' lives, deaths

Yellowstone Cougar Project providing insight to lions' lives, deaths

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Dew claw

The lion's sharp dew claws are used to grab onto an animal during an attack.

Even for a top predator like mountain lions, making a living in Yellowstone National Park is fraught with danger.

That’s evident in talking with Dan Stahler, lead biologist for the park’s Cougar Project. In the past year three cats collared with GPS devices died of natural causes while one was shot outside the park by a hunter.

“As a biologist … whenever you make the decision to collar animals in Yellowstone, you want to understand about their lives,” Stahler said, such as what they eat, how they utilize the habitat and how they interact with other species.

Part of that understanding includes finding out how they die.

In this video, Yellowstone National Park presents facts and insights on the cougar, one of the park's most elusive animals. (Video courtesy of Yellowstone National Park)


The three collared lions that died in the last year demonstrated the variety of dangers that can befall a wild animal.

For example, a male lion that had killed a radio-collared cow elk got caught in an open area by the Junction Butte wolf pack. More often than not, wolves win in such encounters because “it’s a numbers game,” Stahler said, and the cats are usually alone. The cougar was found dead with several wounds.

Another mature tom, considered the king of the park’s Northern Range, may have died trying to swim the Yellowstone River below Hellroaring Creek. The cat’s GPS collar is still sending signals from the bottom of the river where the cat was trapped. Whether or not the cougar was injured when it tried to swim the river, Stahler doesn’t know.

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A female’s death may be the strangest of the three. She got her right wrist stuck between boulders, possibly while trying to catch a marmot. The wrist was broken, probably in her struggle to get free. That also may have been when she knocked another boulder lose that fell onto her.

“That’s the value of GPS collars,” he said, because without a tracking device, researchers would never know what happened to the cats.

A fourth mountain lion collared in the park was killed by Montana Gov. Greg Gianforte during a December hunt north of Yellowstone, sparking an outcry from some conservation groups. Stahler said the lion was an example of wildlife wandering into and out of the park, something wolves, bison and elk also do.

Release location

Members of the Yellowstone Cougar Project struggle to move a newly collared mountain lion to a flat spot where it will be left to recover from sedation. Lions live in steep, rocky country which is one reason they are rarely seen.

A first

The GPS collars immediately proved their worth to Stahler when a 3-year-old male, the first the researchers had collared, was discovered after a difficult search in 2016. Following up on the last known coordinates, the researchers hiked into the steep and rugged Black Canyon of the Yellowstone. There they found a bloody battle scene but no cougar and no signal from the GPS.

Stahler can be heard in an audio post frustrated at the loss of the collared animal. Finally, in a second day of searching, the dead cat was discovered almost 20 feet underground in a boulder field. The young male had likely clashed with a more dominant male and was badly injured. Bleeding heavily with wounds to its forearms, face and the back of its head, the cougar crawled into a crevice and died.

Unable to get the entire cat out, Stahler had to decapitate the animal to retrieve the collar. Once the skull was cleaned, several puncture wounds from a fight with another cougar were evident. The young male, known as M198, was also unique because it was the first Yellowstone lion to have its genome sequenced. Unfortunately, it had only been collared for a month.

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Dan Stahler

Yellowstone wildlife biologist Dan Stahler prepares a sedative as he works to collar a mountain lion in the park for an ongoing study.

The project

So far the Cougar Project has collared 25 cats throughout the course of the study that began in 2014. Fitted with accelerometers that show the position of the cat’s neck, the data the devices generate can also provide information on what the cats are doing and, through calculations, how many calories they may be burning.

They also show another female moving from the north side of the park to the Madison Valley, some 50-miles as the crow flies and on the other side of the Gallatin and Madison mountain ranges.

Cougars leave their mothers when they are 18 months to 2 years old, Stahler explained. Young males may travel up to 400 miles to ensure they don’t interbreed with any relatives. About 20% of young females remain close to where they were raised with the rest dispersing up to 150 miles.

The collared female appears to have given birth to kittens based on its restricted movements noted by the GPS, Stahler said. She is one of five cougars collared in the park. Stahler is hoping to find and collar one more lion this year while there’s still snow on the ground for tracking.


Once darted, one of the Cougar Project crew climbs into the tree to lower the animal to the ground for processing.


Fewer collars are needed because the Cougar Project is testing the use of less invasive ways to track the big cats. This includes an array of 134 remote cameras spread out on a grid for the second winter in a row. The collared animals provide a way to recognize individuals in the 20-second videos the cameras shoot, creating a basis for calculating the density and abundance of the wider population.

Prior to establishing the array of cameras, the team was collecting hair and fecal samples by following cat tracks. Through DNA analysis, the park researchers have identified a population of about 30 to 40 cougars with a density of about 2.1 cats every 100 square kilometers (about 62 square miles). These calculations are very similar to earlier studies done on cougars in Yellowstone.

In addition to allowing researchers a less hands-on way to identify and track cougars, the videos capture high-definition scenarios that can provide great teaching tools for scientists, helping the public understand the lives of the secretive animals few people will ever encounter.

The researchers will also identify every other animal that gets filmed, providing a database for future studies. Last year the cameras filmed a wolverine that, when posted online, caused a stir because the animals are so rarely seen or filmed.

Canine teeth close-up

The male lion's teeth are revealed, demonstrating one of the weapons the cats use.

Big picture

All the data collected on cougars will help scientists compare and contrast the mountain lions’ impact alongside that of wolves, black bears and grizzly bears. Together, the individual stories add to the mosaic that is Yellowstone, providing greater insight to a complicated and dynamic ecosystem that contains a full complement of predators.

One graduate student is currently using the information to try and tease out the effects the carnivores have on the park’s migratory elk population.

“Everyone thinks wolves are a big player,” Stahler said, but cougars actually have a higher kill rate, especially females with kittens. They kill an animal about every six days. More recently, the cougars’ diet has shifted from elk to mule deer, falling to 55% elk vs. 45% mule deer, Stahler added. The other 5% includes everything from pronghorns to mountain goats, bighorns, marmots and foxes.

“The goal is to bring all those components together to understand how Yellowstone operates,” he said.


The male lion hissed once it was treed and before being tranquilized. Adult males can weigh up to 170 pounds and live about eight to 10 years.


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