The Yellowstone Cougar Project Provides Insight into the Life and Death of Lions | State and Region



Even for a top predator like cougars, making a living in Yellowstone National Park is fraught with challenges.

It is evident from speaking with Dan Stahlerchief park biologist Project Cougar. In the past year, three cats fitted with GPS collars have died of natural causes while one was shot outside the park by a hunter.

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

Part of that understanding is finding out how they die.


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

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For example, a male lion that had killed a radio-collared elk was 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 cats are usually on their own. The puma was found dead with multiple injuries.

Another adult tom, considered the king of the park’s North Range, may have died trying to swim in 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 in the river, Stahler doesn’t know.

A woman’s death can be the strangest of the three. She got her right wrist caught between some rocks, possibly trying to catch a groundhog. The wrist was broken, probably in its struggle to break free. It could also be when she knocked over another rock that fell on her.

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

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

Exit place

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

Jacob W. Frank, NPS

A first

GPS collars immediately proved their worth to Stahler when a 3-year-old male, the first the researchers had put on a collar, was discovered after a difficult search in 2016. Following the last known coordinates, the researchers walked in the steep and rugged slopes. Yellowstone Black Canyon. There they found a bloody battle scene but no cougars and no GPS signal.

Stahler can be heard in a audio message frustrated with the loss of the collared pet. Finally, during a second day of searching, the dead cat was discovered nearly 20 feet underground in a field of rocks. The young male had probably collided with a more dominant male and was seriously injured. Bleeding profusely with wounds to his forearms, face and back of his head, the cougar crawled into a crevice and died.

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

Dan Stahler

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

Jacob W. Frank, NPS

The project

So far, the Cougar Project has collared 25 cats throughout the study, which began in 2014. Equipped with accelerometers that indicate the position of the cat’s neck, the data generated by the devices can also provide information on what cats are doing and, through calculations, how many calories they can burn.

They also show another female moving from the north side of the park toward the Madison Valley, about 50 miles as the crow flies and across the Gallatin and Madison mountain ranges.

Cougars leave their mother between 18 months and 2 years old, Stahler explained. Young males may travel up to 400 miles to ensure they do not cross paths with relatives. About 20% of young females stay near where they were reared, with the rest dispersing up to 150 miles.

The collared female appears to have given birth to kittens based on her GPS-noted restricted movements, Stahler said. She is one of five cougars to have a collar in the park. Stahler hopes to find and stick another lion this year while there is still snow on the ground for follow-up.


Once launched, one of the Project Cougar team members climbs the tree to lower the animal to the ground for treatment.

Jacob W. Frank, NPS


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

Before establishing the camera array, the team collected hair and feces samples by following the tracks of cats. Through DNA analysis, park researchers have identified a population of about 30–40 cougars with a density of about 2.1 cats per 100 square kilometers (about 62 square miles). These calculations are very similar to previous studies done on cougars in Yellowstone.

In addition to allowing researchers to identify and track cougars in less convenient ways, the videos capture high-definition scenarios that can provide great educational tools for scientists, helping the public understand the lives of secret animals that few people will ever meet.

Researchers will also identify any other animals filmed, providing a database for future studies. Last year the cameras captured a wolverine which, when posted online, caused a stir because animals are so rarely seen or filmed.

Close-up of canines

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

Jacob W. Frank, NPS

big picture

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

A graduate student is currently using the information to try to untangle the effects of carnivores on the park’s population of migrating elk.

“Everyone thinks wolves are a big player,” Stahler said, but cougars actually have a higher mortality rate, especially females with kittens. They kill an animal approximately every six days. More recently, cougar diets have shifted from elk to mule deer, dropping to 55% elk versus 45% mule deer, Stahler added. The remaining 5% includes everything from pronghorns and mountain goats to bighorn sheep, marmots and foxes.

“The goal is to bring all of these components together to understand how Yellowstone works,” he said.


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

Jacob W. Frank, NPS


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