Plague in Yellowstone Mountain Lions

An adult male mountain lion.

Plague is a highly-contagious, deadly disease caused by the bacterium Yersinia pestis. The Black Death, for example, killed some 75-200 million people from 1346-1353, after which it took 200 years for the world’s human population to recover. But plague is not just a horror of history. It is still very much alive today, living in the soils where we live, work and play. For the most part, we remain unaware of its presence unless a colony of prairie dogs or ground squirrels dies and their carcasses draw our attention. In a new paper just published in Environmental Conservation, we report startling results of plague testing in mountain lions from our Teton Cougar Project. We sampled over a nine year period, overlapping a case in which a boy scout contracted plague in our study area.

We detected plague exposure in 43% of 28 mountain lions tested for plague. Over the same time period, 4 mountain lions died of plague. Other researchers have been documenting high levels of plague exposure among mountain lions as well—along the western slope of the Rockies in Colorado, and in southern California, for example. Some have even speculated that mountain lions could carry the bacterium long distances if a young animal seeking a territory were infected.

We concluded that Y. pestis may be present at higher levels in the Greater Yellowstone Ecosystem than previously thought, and that plague is a concern for local mountain lions. We also believe mountain lions may be a useful sentinel to alert people about the potential risk of plague in areas across the West, because of their current status as a hunted game species. More than 3,000 mountain lions are killed by hunters each year and presented to state and provincial wildlife agency personnel. State personnel could sample these animals, which in combination with the locations of where they were killed, could be used to refine maps of potential exposure to humans. Please note, that we are not arguing for increased mountain lion hunting, or that plague testing is sufficient reason to hunt mountain lions. We are only pointing out that where they are hunted, they could provide useful data to improve human safety.

Last, we would emphasize that the average person has essentially zero possibility of contracting plague from a mountain lion. So please, do not read into our results as a reason to fear mountain lions. The vast majority of people in the USA will never be lucky enough to see a wild mountain lion, let alone be close enough to interact with their body fluids. Nevertheless, hunters and others handling mountain lions in the Yellowstone region should be aware of the possibility of exposure. Knowledge is power. In 2007, my friend and mentor, Eric York died from plague he contracted from a mountain lion in Grand Canyon National Park. His terrible death reverberated through the research community, causing shock and mourning. And it could have been avoided if people had considered the possibility that he had plague and administered appropriate antibiotics. Eric was one of the best field biologists I’ve ever met. He drank from a coffee mug each morning labeled “FTP,” short for “For The Puma.” Everything he did, dawn to dusk, was for mountain lions.

For those who might be interested, please follow our work on Facebook.

Mountain Lions as Ecosystem Engineers

Adult female mountain lion, Olympic Peninsula. Photograph by Mark Elbroch

The keystone rock is an arch’s linchpin providing structural strength and integrity—remove it, and the structure topples and falls. Ecosystems function in much the same way. Keystone species are animals that disproportionately influence their environment, and often those that best support ecosystem health and biodiversity. An ecosystem engineer is one type of keystone species—they are animals that create or modify habitat for other animals, generally increasing biodiversity in local areas and the amount of types of habitat available for wildlife.

Think of American beavers. Beavers dam streams, which changes water speed, water depth, and subsequently, water temperature. Deep, still beaver ponds that sit and soak up sunlight support different fish, plant, and bird life than the fast-running portions of the same stream. Without beavers, the stream as a whole would support less kinds of flora and fauna, which we collectively call biodiversity.

In research recently published in the prestigious journal, Oecologia, we show that mountain lions are ecosystem engineers that create essential habitat for carrion-dependent beetles. It is the first research to show that an apex predator plays the role of engineer. In collaboration with graduate researcher, Josh Barry, and Dr. Melissa Grigione at Pace University, we collected and identified 24, 209 beetles across 18 sites, representing 215 unique beetle species. The carcasses abandoned by mountain lions were not just food for beetles, but the very places beetles spent their lives, hiding from predators, seeking mates, raising young, and morphing from larvae into adult forms that dispersed in search of the next carcass to begin the cycle all over again.

Photograph by Josh Barry / Pace University and Pace University

Ecosystem engineers and other keystone species are those animals that are the critical puzzle pieces that connect to the most other pieces, they are the species that disproportionately hold ecosystems together, and they are the species that require conservation attention to ensure their populations are healthy. Mountain lions are one such species. Mountain lions create more large carcasses than other predators (for example, wolves tend to dismantle prey into many small chunks), which recent research has shown is more important to ecosystem health. They feed more mammals and birds than any other predator, increasing the number of animal interactions (e.g. links in food webs) so essential to maintaining ecosystem resilience. And they are ecosystem engineers on top of this as well.

Mountain lion predation, we’re learning contributes to local biodversity and ecosystem health and more. Photograph by Mark Elbroch

We are only just beginning to unravel the positive roles that mountain lions play in supporting healthy natural systems, and they are already startling. Evidence suggests that maintaining healthy mountain lion populations across the Americas is an important step to maintaining healthy ecosystems that sustain complex biodiversity, including human beings. Put another way, when we aid mountain lions we ultimately help ourselves.

Follow Panthera’s Puma Program on Facebook to learn more about mountain lions and our conservation research.


Common Sense Conservation to Keep Kittens Safer

Three of F61’s kittens in a typical fortress of downed wood, in which she gave birth. Photo by Mark Elbroch.

An early snow had painted the landscape completely white, and we were navigating the slippery roads of backcountry northwest Wyoming as part of Panthera’s Teton Cougar Project. We paused to look at footprints of a mountain lion we called F61, where she crossed the road and climbed towards the ridgeline. Just up the road, we found a houndsman’s truck tucked up against the trees. I turned off the engine and we stepped out into the crisp, still air. We did not hear the baying of hunting hounds—perhaps he hadn’t found her. Just ravens and wind.

We knew that F61 was nursing four tiny kittens at the time, tucked up in a woody fortress to the south across the river. If she were killed, four more mountain lions would die. It’s an unavoidable reality that, on occasion, hunters unintentionally kill females with dependent young—subsequently dooming the kittens along with their mother.

This is why we conducted new research just published in the Wildlife Society Bulletin. We set out to study female movements and behaviors while they were caring for the youngest and most vulnerable kittens in the den (See this blog for a description of a puma den). “Denning” is the period beginning when kittens are born and ending when they start traveling with their mother to her kill sites.

F61 with her 4 tiny kittens in the den. Photo by Mark Elbroch

We used 12 dens to determine the average length of denning, and 34 dens we documented over the course of our work to determine the following—if we delay legal mountain lion hunting until December 1 each year, we can avoid the denning period for 91% of mountain lion families.

Such a change would allow hunters the best opportunity to detect mountain lion family groups in the field, and to avoid inadvertently hunting females with kittens. It’s also a change that provides mountain lion families greater safety while their kittens are most vulnerable. It’s also a change that reflects a growing appreciation for predators in an evolving world.

In my mind, it’s just common sense conservation.

The morning after our encounter, Michelle Peziol, the Project Manager of Panthera’s Teton Cougar Project, followed F61’s trail from where we’d found her tracks crossing the road. Climbing the hill and traversing the ridge line, she saw that the mountain lion’s trail was intercepted by a hunter on horseback and his hounds. She discovered the tree where F61 had sought refuge. The area was a mess—churned up by the feet of cat, baying hounds, horse, and man.

A portrait of F51 and her kitten. Photo by Mark Elbroch

At the same time, I toured F61’s usual haunts and found her using the beacon in her collar. The hunter had let her go. I caught up with him several days later. He was gracious and recounted a beautiful day on the mountain—his first day hunting of the year, he said. He described F61 well, saying he’d noticed her collar and realized she must be one of the mountain lions we studied. He valued research, so he hauled in his hounds and walked away, letting her be.

The hunter had spared F61, and in doing so, had saved the lives of four more mountain lions, too. He was more than relieved when I told him.

This is simple change that can aid mountain lions right now. Spread the word: Delay mountain lion hunting seasons in western states until December 1 to protect the youngest kittens. It’s common sense conservation that we can apply immediately to increase protections for mountain lion families in hunted populations, supporting the shared goals of conservation scientists, wildlife advocates, and hunters alike.

Follow our work on Facebook as well.

Two Washington Talks on Mountain Lion Social Behaviors in February

For anyone interested in mountain lion social behaviors, please join me on February 1st in Port Angeles, Washington or February 24th in Duvall, Washington.

Feb 1 at Studium Generale in the Little Theater, Peninsula College:

1502 E. Lauridsen Blvd./Port Angeles, Wa. 98362.

Here is a link for directions:

Additional directions: The “Little Theater” is centrally located in the Pirate Union Building (“The PUB”), which is directly above (south of) the main parking area. If you walk between the library and the clock tower building, you will come right to it.


Feb 24 at Wilderness Awareness School, Duvall WA.

Contact: Marcus Reynerson <>

I don’t actually know exactly where the presentation will occur–contact Marcus for details.
The office of WAS is at 26425 NE Allen St, Ste 203, Duvall, WA 98019. Their main campus is Linne Doran and directions are found here:
Thank you for your interest.