A new population estimate of mountain lions in the southern reaches of the Bitterroot suggests there are at least twice as many animals as wildlife managers initially thought.
Researchers from Montana Fish, Wildlife and Parks and the University of Montana released results of the DNA-based estimate of adult mountain lions this week.
The research team used cutting-edge population modeling techniques coupled with DNA sampling collected from both live and hunter-harvested animals to develop estimates that predicted a population of 85 adult lions in the West Fork and 82 in the East Fork.
Those numbers did not include juveniles or kittens.
The research project followed initial findings from a large-scale, three-year Bitterroot elk study that showed mountain lions were the main predator of elk calves in the southern portion of the valley.
“When mountain lions started turning up as a major cause of elk calf mortality in their first year of life, we wanted to establish a baseline for the lion population in the valley,” University of Montana researcher Mark Hebblewhite said Wednesday.
DNA samples of mountain lions were collected from Dec. 12, 2012, through April 2013 under the direction of FWP’s Kelly Proffitt and Hebblewhite.
A field team, led by FWP’s Ben Jimenez, collected DNA samples in gridded portions of the study area based on the habitat type and quality.
The team used mountain lion hunting dogs to tree the animals. DNA samples were collected by using an air gun loaded with hollow darts that were fired into the side of the lion and collected after they fell off.
Other DNA samples were collected from scat, hair and lions killed by hunters during the period.
Hebblewhite was surprised at the number of new lions the researchers found in the same locations.
“We really did find a lot of mountain lions over that period of time,” Hebblewhite said. “We had four houndsmen teams working with us. We expected at a certain point that we would start bumping into the same mountain lions.”
Instead, Hebblewhite said, the researchers were still finding new lions even as the four-month project came to an end.
Using DNA as a way of identifying the lions has benefits when it comes to convincing the general public of the validity of the study.
“That’s the nice thing about DNA,” said Hebblewhite. “It’s pretty foolproof. People understand that it works in the courts. They see it as indisputable evidence.”
The DNA samples were analyzed by the U.S. Forest Service Rocky Mountain Research Station in Missoula.
From the 80 samples collected by the team, researchers were able to identify 62 unique lions by their genetic fingerprints. That DNA-verified sample was higher than the initially estimated population for the area.
It also represents the lowest possible number of lions in the southern Bitterroot.
That initial population prediction in 2012 was determined by using information gleaned from previous research projects in other parts of the state.
This time around, researchers used a new cutting-edge statistical analysis model to make its estimate of 167 lions in the southern Bitterroot. The work of the researchers will be peer-reviewed this year and published in a scientific journal.
“Traditional approaches to estimate mountain lion abundance focused on radio collaring and counting individual lions, but recent advancements in lion DNA sampling and spatial estimation methodologies made it possible to get a more accurate estimate of lions in the Bitterroot,” said Proffitt. “These new techniques reduced time, cost and the number of lions that had to be handled and made it practical for us to obtain an improved lion population estimate to the Bitterroot.”
The models being used in the Bitterroot were initially developed by researchers tracking tigers in India, Hebblewhite said.
“These SCR (spatial capture recapture) models have become the gold standard for counting tigers across their range,” he said. “They were developed in part specifically to count tigers, as so, their application to mountain lions is a natural extension.”
Hebblewhite said the research team spent several months poring over the lion population predictions in the Bitterroot to ensure that they were sound.
The results show a population that’s not only higher than expected, but also one that is on the higher end of other lion populations that have been studied across the West.
Proffitt said there are several factors that could have contributed to that higher-than-average abundance of mountain lions in the area.
“The combination of low to no female lion harvest during the past 10 years, combined with good quality lion habitat and diverse prey likely result in a high density mountain lion population,” she said.
The researchers’ work in the Bitterroot in combining information on habitat quality, search effort, and encounter likelihood in a computer-based model to estimate the lion population represents an advancement in the science.
The pairing of DNA sampling techniques with habitat quality modeling is something new, Proffitt said.
The next step in the ongoing elk and mountain lion research project in the Bitterroot will be to see if increased hunting pressure on mountain lions will impact elk calf survival.
FWP wildlife manager Mike Thompson said the state will use the new information to re-evaluate the lion harvest quotas for next season.
The state has established a goal of reducing the Bitterroot Valley’s lion population by 30 percent over the course of three years. The initial lion harvest quotas were based on the first 2012 population estimate.
To learn more, people can go to fwp.mt.gov and follow the links to “Fish and Wildlife” and “Conservation” or contact FWP at 542-5500.
Reach reporter Perry Backus at 363-3300 or firstname.lastname@example.org.