Hiking into the backcountry in search of animals cached by a mountain lion may sound unnerving, but it’s all in a day’s work for Cyrena Bedoian. Each day Bedoian, a mountain lion ecology technician with the University of Wyoming’s Haub School of Environment and Natural Resources, goes to the Wyoming Game and Fish Department’s regional office in Casper to get coordinates of potential mountain lion cache sites. She plans how to get there and heads out to investigate. She drives as close as she can and hikes in to see what she can find — that hike could be a quarter-mile from the road or deep into rough terrain. She never knows what her day will look like when she wakes up.


Cyrena Bedoian, mountain lion ecology technician with the University of Wyoming Haub School of Environment and Natural Resources, utilizes a telemetry receiver to see if any collared mountain lions are in the area. When she walks into a potential mountain lion cache, she checks to see if the collared mountain lion is still in the area to limit surprise encounters. (Photo by Tracie Binkerd/WGFD)

Bedoian locates these sites to collect tissue samples as part of ongoing research on how mountain lions prey upon deer — especially those with chronic wasting disease. Just as Bedoian doesn’t know what to expect when she gets up for the day, researchers leading the study don’t know precisely how the research will be used in the future. With so many ways the information can be applied, it all comes down to the data.

Targeted or random?
As part of this ongoing study, researchers are looking into how mountain lions predate on mule deer. The large cats commonly prey upon deer as a food source, and questions persist about how CWD may change their habits, if it does at all. CWD is a fatal disease of the central nervous system in deer, elk and moose. Although early in the disease animals may show no clinical signs of the illness, as the disease advances animals may show weight loss, reluctance to move, excessive salivation, droopy ears, increased drinking and urinating and eventually death.

Is it possible mountain lions prey more on deer with CWD? Or do they avoid animals with the disease? Mountain lions may be able to discern behavioral changes due to disease before humans, so is it possible they are removing infected animals before they get to an advanced stage? Researchers hope to get answers or at least gain some insight into these questions through this study, a partnership between the Wyoming Game and Fish Department and the University of Wyoming.

A study in Colorado published in the Royal Society’s Biology Letters in 2009 found a higher occurrence of CWD in deer killed by mountain lions when compared to deer killed by hunters in the same area — indicating mountain lions may target CWD-infected animals. But the study came with limitations. Over three years, the study documented 108 kill sites, 62 of which were mule deer.

Even with a small sample size, that study piqued the interest of Justin Clapp, a large carnivore biologist with Game and Fish. He wanted to look deeper into the issue with a more robust study looking at more mountain lion kills than in the previous study.
“I wanted a study that could give us as much information as possible so we can make better management decisions for mountain lions and mule deer,” Clapp said. “Further research could support what’s been found, or it can challenge those findings.”

He began working with colleagues to identify an area where they could look at numerous cache sites from several different mountain lions. Justin Binfet, Game and Fish wildlife management coordinator in the Casper Region, thought his area would lend itself perfectly to the cause. Not only is the terrain occupied by mountain lions, but the Casper Region is home to the Bates Hole/Hat Six mule deer herd, which is unfortunately known to have a high prevalence of CWD. Together, Clapp and Binfet have led the research in Wyoming.

“Through this research we can better understand what’s already happening in the ecosystem,” Binfet said. “We don’t know yet what we’ll do with this information. Ultimately we want to know what role mountain lions are playing in the CWD picture. Does mountain lion predation reduce CWD transmission by removing sick animals in earlier stages of the disease; does it further stress a herd that may be struggling from various environmental factors such as disease; or does it have little effect on long-term population trajectory of the mule deer herd?”

Keeping on track
Beginning in 2019 crews placed GPS tracking collars on mountain lions in the Casper Region. Once deployed, the collar collects location data of the mountain lion every three hours. Once per day, those points are transmitted to a satellite and then to researchers.


Daniel Thompson, Game and Fish large carnivore section supervisor, left, Justin Clapp, Game and Fish large carnivore biologist, right, and Joe Holbrook, assistant professor at the University of Wyoming, back, check vital signs on an immobilized mountain lion that was recently collared. (Photo by Justin Binfet/WGFD)

Armed with information on where the cat has been, Clapp uses a model to predict if a location is a kill site based on clusters where the mountain lion spent its time.
“There’s a variety of models that have been developed across numerous mountain lion studies,” Clapp said. “The model we use is mostly based on a cluster of points showing where it’s spending more time. We can look at how concentrated the points are over three-hour periods, how long the animal was there, the time of day and how many visits the animal made to predict if a location may have a cache.”
Once potential kill sites are identified, the information is sent to the boots on the ground who attempt to locate the cached prey. The hike to these areas can be challenging, but the work doesn’t end with the walk. If the biologist or technician, like Bedoian, finds a carcass in good enough condition, they collect biological samples — and it isn’t an easy task.  

When Bedoian locates a cached kill, it can take effort to maneuver the animal into a position so she can get the samples she needs. It can be a challenge to move an adult deer or an elk calf by yourself. Then she uses tools to collect tissues that can be tested for CWD, including lymph nodes, tonsils and obex — tissue near the spinal cord where it enters the brain.


Bedoian records information at a mountain lion cache in the Casper Region. At cache sites, like this one with an elk calf, she collects biological samples and documents observations. (Photo by Tracie Binkerd/WGFD)

Technicians don’t limit themselves to tissues known to have CWD prions. They gather as much evidence as possible, never knowing what will apply to this study or perhaps have implications for other researchers. Technicians collect bone marrow, muscle tissue, scat, ears and other biological samples. These items can be used to evaluate the animal’s overall health and genes and could even be used to develop or assess other CWD detection methods.

They also gather evidence of how the prey died, evaluating whether it was killed by a mountain lion or perhaps died of another cause and was scavenged by the cat. This could demonstrate if mountain lions kill more animals with CWD or perhaps feed on them after they’ve already died.

“We can collect a lot of information in one go,” said Clapp. “The data we can provide for other research has been massive. It’s nice to focus on our own research while still optimizing our data and answering questions while tracking a mountain lion.”

Challenge of coexistence
Collaring cats and tracking down cached prey is only part of the struggle researchers have to overcome. As a large carnivore, mountain lions can induce strong feelings in people.

“Mountain lions are an animal that people seem to love or hate,” Binfet said. “It is a sensitive issue. Then when you consider they prey on mule deer, some people really want any cause of deer mortality to be eliminated.”

These strong feelings about mountain lions can complicate a project that often relies on landowners to allow access to kill sites. The project would never have gotten off the ground without landowners who allow researchers to collar mountain lions on their property and provide access when a potential kill site is identified.

“We really want to thank landowners who have made this possible,” Clapp said. “It takes a lot of sacrifice from them to allow continuous access from our employees who go into the field to collect data daily.”
Binfet echoed those thoughts. 

“We really couldn’t do this without the landowners who are participating in this study and allowing researchers on their land. I’m thankful we have some landowners who are willing to help us in this endeavor,” Binfet said. 


A female mountain lion with a collar at Deer Creek in the Casper Region. Even when a mountain lion has been collared, equipment malfunctions can make gathering data difficult. (Photo by Justin Binfet/WGFD)

No matter how someone feels about mountain lions, this study can have long-lasting benefits for wildlife.

“This study looks at how mule deer and mountain lions coexist and the influences they have on each other,” Clapp said. “So this is a win for everyone who likes Wyoming’s wildlife.”

Once a mountain lion is collared, keeping it in the study can create a challenge, too. GPS collars can go offline for several reasons, including malfunction or running out of battery. Some mountain lions are removed through hunting or die of natural causes. Researchers have had to place collars on several cats to keep a good sample size with continuous kill sites. Twenty-two different cats have been collared for the study so far, with as low as five sporting active collars at once when cats are lost.

“Even with a low number of cats at one time, they are all moving and making kills,” Binfet said. “So we’re still able to get out to these sites and collect samples.”

Getting samples can be a challenge, too. It can take time for a cluster to emerge that may indicate a kill site, then the data still needs to be transmitted and evaluated before someone can go to the area. This process can take up to three days from the time an animal is killed by a mountain lion before a biologist or technician can get to the site. During that time the animal is fed on by the mountain lion and other animals. While the samples collected aren’t usually from areas mountain lions eat first, scavengers can spread remains, making it impossible to locate the parts needed for CWD testing.

Not every predicted site has a cache — about 60 percent of the possible sites have prey at them. Then, not every kill is an animal that may have CWD. The disease can be found in elk, deer and moose, so other prey can’t be sampled for it. About 50 percent of the sites with a cache have deer, and just under 25 percent have elk. Out of those, samples are typically collected from about 25 percent of deer and 45 percent of elk. Still, with over 1,500 sites investigated since the study began in 2019, crews are confident they will acquire enough samples for a robust assessment.

It’s too early to draw conclusions from the study. Data collection at kill sites is expected to be complete in spring 2023. Once all the information has been gathered, the data can be further evaluated and applied to wildlife management in Wyoming and the West.

— Tracie Binkerd is the editor of Wyoming Wildlife.