Results of a two-year study on mountain lion density in the Western Slope confirmed a robust mountain lion population that exceeded some of the modeled estimates.
The Colorado Parks and Wildlife study effort began in 2020 with a study area in Middle Park, between Kremmling and Granby, followed by a second study area in the Gunnison Basin that began in 2021.
The series of studies approved in 2020 by the CPW Commission showed an average 2.5 “independent” lions per 60 square miles during the winters of 2021-22 and 2022-23 in Middle Park and an average density of 4.2 lions per square miles during the winters of 2022-23 and 2023-24 in the Gunnison Basin.
In all, CPW marked or collared 48 mountain lions in the Middle Park study area and just over 50 in the Gunnison Basin.
“We were satisfied to see that our measured estimates of lion density from our winter field seasons are equal to, and in some cases higher than, the lion density projections we use when making harvest management decisions,” said Mark Vieira, CPW’s carnivore and furbearer program manager. “Data confirmed that current management is meeting agency goals of providing opportunity while managing for healthy and robust populations.”
As part of the West Slope Mountain Lion Management Plan that was approved by the Parks and Wildlife Commission in 2020, CPW began the studies by estimating how many adult and subadult mountain lions live in different habitat types and areas of the Western Slope.
“These study areas were selected to be representative of Colorado’s lion habitat with balanced habitat types, landownership and lion harvest levels,” Vieira said.
You can view this video on the Western Slope Mountain Lion Density Study.
The study involved hundreds of hours from CPW staff, wildlife biologists, district wildlife managers and researchers who captured, marked, collared, and monitored lions over the course of two years.
Densities were estimated using camera-based “mark-resight estimates,” a management technique that uses motion-activated cameras to “mark” and “resight” animals over time. It allows researchers to make informed estimates of population density and trends.
In the mark phase, CPW said its biologists placed ear tags and GPS collars on mountain lions.
In the resight phase, the trail cameras match then record photos of the animals and compare how many of their tagged cats are in the same area compared to uncollared cats.
By identifying how many marked individuals are seen in the photos and combining that with photos of unmarked individuals, researchers can estimate the total population size in the study area using mathematical models. GPS collar location information is used to account for lions that move on and off the study area during the resighting period, as well.
These kinds of studies allow CPW to make science-based decisions when it comes to managing populations, if necessary. It also will begin to show trends as more housing is developed that draws more people into historically unincorporated parts of Colorado.
The density study will continue this winter in the Book Cliffs north of Grand Junction. Lion capture work will also be taking place this winter in a fourth study area east of Durango.
“These results show that the lion populations in these representative study areas are strong,” Vieira said. “This combination of GPS collars and ear tags on lions paired with trail cameras across large representative study areas is showing us that parts of Colorado appear to have high lion numbers compared to studies of lions in other states.”