Counting Mountain Lions a Major Challenge

No large North American mammal is more elusive than the mountain lion.

Counting Mountain Lions a Major Challenge

Mountain lions are experts at being invisible, which can make it incredibly difficult for biologists to achieve solid population estimates. 

For decades, hunters have remained one of the best resources. All Western states require hunters to report kills, and with good snow cover for tracking, high success rates can be an indicator of a healthy population. 

Researchers in Wyoming helped take that idea to the next level in the early 2000s when they developed a method to predict population size using the sex and age composition of lions harvested by hound hunters. That’s because the likelihood of a hunter killing a specific sex or age class of lion reflects the percentage of each of these categories in a population and their relative vulnerability to harvest. Complex math for sure, but these calculations proved themselves in the study, and Wyoming has used this tactic for tabulating cougar populations ever since. 

In 2019, Montana adopted a very different strategy based on the success of a five-year study in the upper Clark Fork watershed near the town of Philipsburg. 

Montana Fish, Wildlife and Parks (FWP) now partners with local hound handlers to help count cougars statewide. From December through mid-April, these contractors take to the woods searching for lion sign. Finding fresh tracks, they send out their hounds to trail and tree the lion, then shoot them with a biopsy dart to collect a muscle sample before releasing the cat. That sample is sent to a DNA lab to identify individuals within the population, which may be recaptured over the course of the winter. Biologists then combine that info with data from hunter kills, habitat quality, miles of accessible roads and other variables to gain a solid estimate of how many lions are on the prowl. 

Molly Parks, FWP carnivore coordinator, says this partnership with hound handlers helps build public trust since they know the country and the lions as well as anyone living. 

“The handlers have just been amazing,” Parks said. “They’re super passionate about this work and help to make sure it’s rigorous science done right. Plus, they help communicate the results to the public since they’re pretty much all hardcore lion hunters themselves.” 

The same can’t be said in places such as California, which banned cougar hunting in 1990. The state lacks hunters invested in lion conservation and license dollars to help with management — not to mention hound handlers to aid with research. The Department of Fish and Wildlife states clearly on its website that the number of cougars in the state is unknown. 

In the West, mountain lions roam virtually every location that elk do — and in most areas, they are elk’s primary wild predator. Conserving both species in concert requires knowing how many sharp-toothed mouths are feeding on herds of deer, elk and other big game. 

Idaho has been a proving ground for lion research dating back to the first long-term cougar study in the Frank Church Wilderness during the 1960s. Idaho biologists are continuing that tradition, breaking new ground again through the wide-spread use of camera traps. 

Biologists use devices similar to the trail cams sold in most sporting goods stores and deploy them by the hundreds in various locations across the state. Laid out in grids, each camera is synchronized to take photos at the same moment. If a lion (or moose, wolf, etc.) appears in one of the millions of images taken over the course of the year, that capture is recorded and later put into an algorithm that combines information coming from hunters to extrapolate real population numbers. 

In 2021, Idaho removed all male and female mountain lion quotas statewide, but still requires a mandatory check of all harvested mountain lions to gather sex and age data. 

Colorado, which is home to more elk than any other state, is using similar counting methods. The state Parks and Wildlife (CPW) department is entering the third year of a study to understand the density of mountain lions on the Western Slope where their largest herds roam. 

Research began in 2021 in Middle Park in CPW’s Northwest Region, then shifted focus to the Gunnison area in CPW’s Southwest Region in 2022. The study will alternate between these two regions each year during the decade-long project. 

CPW researchers aim to assess cougar population density by strapping GPS collars and numbered ear tags on at least 25 adult cats each year. And like Idaho, they’re also placing numerous remote cameras across these areas. 

“While other mountain lion research projects in Colorado are and have been done to answer a range of biological questions, we are really laser focused on getting a better estimate of the numbers of mountain lions here,” said Brandon Diamond, CPW area wildlife manager in the Gunnison area, in a press release. “It’s an exciting time. Predator management is a big deal and having more data to rely on will only enhance our local and statewide management.”

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