Mountain Lions Offer More Than a Pretty Face and a Fine Physique

Mountain lions are hell on zombie deer and elk roaming the Rockies.

The map below tells the story of mountain lions and their disease-cleansing work on the iconic deer and elk herds that are emblems of the mile-high ecosystems in the Rocky Mountain State and other parts of the West.

Colorado has had a long-running epidemic of Chronic Wasting Disease (CWD), an incurable, fatal neurological disease, akin to Mad Cow Disease. It is a plague for cervids (i.e., deer, elk, and moose) — infecting 42 out of 51 deer herds and 17 of 42 elk herds in the state.

CWD eats away at the brain of an infected animal, disorients it, and ultimately kills the victim. The disease first emerged 50 years ago in cervid populations kept in captivity by researchers at Colorado State University. Wild deer and elk mingled with the captive cervids, and the genie has been out of the bottle ever since. 

It’s horrible for the animals, and it’s bad news for the state of Colorado. Deer and elk license sales alone account for two-thirds of hunting revenue for Colorado Parks and Wildlife. The related economic activity is a boon for rural communities throughout the state. If deer and elk herds were to be dramatically depleted in the decades ahead, as some predict, it would send the rural economy into a tailspin.

CWD also has zoonotic disease potential, with some scientists concerned that it can infect hunters and their families if they eat diseased animals. The U.S. Centers for Disease Control and Prevention advises against consuming deer or elk meat harvested from CWD-infected animals because of its potential to infect humans. The human form of CWD is Creutzfeldt–Jakob disease.

Fortunately, nature has in place a check against unmitigated spread of CWD among those animals. A new report by Jim Keen, DVM., PhD, a former USDA veterinarian and infectious disease scientist and the director of veterinary science for the Center for a Humane Economy, reveals that mountain lions play a key role in reducing the spread and the incidence rate of CWD in deer and elk. Since the disease is incurable, the predatory behavior of mountain lions, bobcats, and wolves may be the only way to arrest its spread and cleanse the wild deer and elk populations.

Lions on the Hunt for CWD-Infected Deer and Elk

Dr. Keen’s report, Big Cats as Nature’s Check Against Disease, outlines how mountain lions preferentially prey on sick deer and elk, bringing major ecological and economic benefits to Colorado. Their predation, which can reduce the incidence of CWD, underscores the ability of native cats to cleanse deer and elk herds of the brain-wasting disease.

“With no vaccine or cure for Chronic Wasting disease, wildlife managers are struggling to find solutions,” notes Dr. Keen. “Perhaps the best policy response at the moment in Colorado is to stop killing 500 or so mountain lions a year that conduct population cleansing at no cost to the state and that protect the long-term health and viability of cervid populations.”

The report details at least four lines of evidence supporting predator cleansing: 

• Predator-prey ecology & disease modeling. Mathematical models suggest that predation by mountain lions (and wolves) can significantly reduce CWD prevalence over time.
• Empirical observations. Field studies in Colorado show that mountain lions are more likely to prey on CWD-infected deer compared to healthy deer.
• Laboratory experiments. Research indicates that CWD-infected proteins can become inactive after being digested by coyotes, mountain lions, or bobcats, reducing environmental contamination. If not ingested by a predator, a diseased protein in an infected animal can survive in the environment for years and perhaps even a decade.
• Disease biogeography. CWD tends to be much less prevalent in areas where wolf or mountain lion populations can freely prey on cervids. There are CWD-free ecosystems, including the upper western Great Lakes region where gray wolves prey on white-tailed deer, and in the Greater Yellowstone basin where wolves, mountain lions and bears prey on deer and elk. There are many counties in Colorado where lions live and CWD has no foothold.

The new report implicitly calls into question the long-standing practice of trophy hunting of mountain lions in Colorado. Animal Wellness Action and the Center for a Humane Economy are helping lead a coalition, consisting of 100 organizations, that has qualified an initiative for the November 2024 ballot.

Trophy Hunting of Lions Is a Ruthless, High-Tech Enterprise

Trophy hunting of mountain lions has become high-tech and highly commercialized, with guides guaranteeing kills of trophy cats, mainly for out-of-state hunters. The hallmark of trophy hunting is to kill a large-bodied animal, with the seasonal take being about 500 lions a year (with 53% male and 47% female in the 2023-24 season).

One guide advertising on-line charges $8,500 for a “[n]ear 100% opportunity” to kill a “mature cat.” Deploying “trucks, snowmobiles, and other off highway vehicles,” he and his team “start our days very early driving roads looking for mountain lion tracks. Once we have a track located, we release hounds and catch your cat. Using GPS technology we track the hounds and precisely locate where they treed your trophy. We then determine the easiest route to take you into your trophy.”  

The guide notes that “[m]ost hunts will be based out of our home where clients will have their own private bed, bath and living room area. Weeks where we choose to travel to further hunting areas, lodging will be based out of a nice toy hauler RV, or possible motels in the nearest town. Some areas we will stay in a rustic modern cabin with most of the luxuries of home.”

In short, Colorado has become a commercial playground for out-of-state hunters who outsource the chasing and cornering of the animal. The “hunt” is reduced to shooting a terrorized animal from a tree, with no escape possible. It’s an arboreal canned hunt. The kills are guaranteed, and the lions don’t have a chance.

The killing of mature adult males removes the most efficient animals skilled at killing traditional prey. And the annual killing of as many as 250 females, many of them with kittens who become orphaned and die, impairs the collective work of lions to target CWD-infected sick deer and elk.

“You don’t have to be a wildlife biologist like me to understand that mountain lions play a critical role in Colorado and western ecology,” said Elaine Leslie, Ph.D., a wildlife biologist in Durango and former Chief of Biological Services for the National Park Service. “These animals are an antidote to disease in deer and elk, selectively removing animals that threaten to spread disease and ensuring the protection of Colorado’s biodiversity, and a key part of our rural economy.”

Even major hunting groups that have fallen in line with their brethren to oppose the ballot measure have previously recognized the long-term threat of CWD to the health of prey populations. CWD is “the biggest threat to the future of deer hunting,” according to the Teddy Roosevelt Conservation Partnership, while the National Deer Association calls CWD “the most serious long-term threat to the future of wild deer and deer hunting that we face today.”

Still, because of their long-held hostility to mountain lions and other native carnivores, these groups oppose the ballot measure to halt cruel and unsporting commercial killing of native cats.

“These predators are often seen as competitors with hunters, but they appear to play a vital role in stemming more extreme spread of CWD,” noted Dr. Keen. “If you want to protect hunting and other forms of wildlife-associated recreation associated with deer and elk, then protect mountain lions and allow them to deliver their gratis predator-cleansing services. Mountain lions are a deer and elk hunter’s best friend.”

When CWD becomes highly prevalent in deer and elk populations, as it has in parts of Colorado and dozens of other states, it threatens to slowly erode cervid productivity and may make deer and elk hunting unsustainable. According to population models, CWD may, over a 50-year horizon, substantially reduce or even end hunter take of cervids in large parts of Colorado. The direct economic value of deer and elk hunting and wildlife-watching likely exceeds a billion dollars annually in Colorado. That means that passing a lion-hunting ban, and allowing the animals to do their work, would provide billions in practical services and value in the decades ahead to rural Colorado.

“Since all human efforts to control CWD to date have failed, maintaining ecologically viable apex predator populations represents our best hope at controlling CWD,” noted Col. Thomas Pool, DVM, MPH, a lifelong hunter and rancher from southwest Oklahoma and former chief of the U.S. Army Veterinary Command. “Ending trophy hunting of mountain lions in Colorado is critical to maintaining the billion-dollar deer and elk hunting and wildlife watching economies across Colorado.” Dr. Pool is now senior veterinarian with Animal Wellness Action.

The Colorado ballot measure is about stopping the killing of lions and bobcats for their heads and beautiful coats. It’s also about protecting the big cats who keep nature in balance. Coloradans have a 100-percent guaranteed chance to stop the unacceptable abuse of these remarkable animals who play such a vital role in keeping other wildlife, central to the economy and culture of the state, healthy and robust.