An extensive study of mountain lions on the Front Range, gradually nearing completion, has yet to put a number on the animals' population here. But estimates suggest it might be at the higher end of what experts have long considered the likely numerical range.
"Based on the captures we've had and some of our preliminary results, we'll likely show the lion densities are toward the upper end of what's been reported in the literature," said Mat Alldredge, mammals researcher for Colorado Parks and Wildlife and leader of the Front Range Cougar Study, focusing on Boulder and Jefferson counties.
"The literature from all over the West has been between one and three, or almost four, independent lions per 100 square kilometers — which isn't very many, when you think about it. I think we're in the threes," Alldredge said.
"Independent," Alldredge explained, means a lion that is no longer with its mother, is hunting independently and establishing a home range of its own.
The study has included dozens of specialists within Parks and Wildlife, Boulder and Jefferson counties, the city of Boulder as well as a half-dozen graduate student assistants, and has lasted for eight years. It is still expected to extend into 2016.
Alldredge said a key remaining piece is to try to estimate with greater precision the local population of the animal known scientifically as puma concolor, or cat of one color — which holds the Guinness record for animal with the greatest number of names, at over 40 in English alone.

Researchers are not now able to say that the number of mountain lions — or cougars, pumas, painters, catamounts — prowling the Front Range has changed significantly in recent decades.
"The number of people seeing lions, or reporting lions, has certainly gone up — but that doesn't mean there's more lions," Alldredge said. "There's more people out there looking, too. But there's certainly a healthy lion population."
The study was sparked by an uptick in calls that Parks and Wildlife district wildlife managers were receiving several years back from people alarmed over encounters with the animals, as the urban-wildland interface pressed farther and farther into the animals' rugged natural turf.
Close encounters continue. And experts said that even though the animals' reclusiveness means we often don't actually see them, they can still be close at hand.
Jalali Hartman, who lives in the foothills enclave of Wall Street in the Fourmile Canyon area, said one lion stayed in his neighborhood not long ago for about a week, killing multiple deer.
"I remember an experience where one Saturday morning something heavy had jumped off the cliffs onto my roof and ran off quickly scaring the dogs quite a bit," he wrote in an email.
"As I was out in the yard scanning the hill for it while my heart was pounding, a group of cyclists went by on the road not 20 feet away completely unaware what I was doing out in the yard. As my heart was pounding it struck me that it really does add a level of stress to live so close to these predators."
'The fear sets in'
People's attitudes to lions in their midst is one of several issues the study has been examining.
"If a lion is not in their area and they haven't been having problems with them, people are pretty open — they like the idea that lions are there," Alldredge said. "When they have a lion in their neighborhood, and it has killed a deer or a pet or two, all of a sudden the fear sets in and they don't want lions around — which is going to be interesting in the future as human populations increase and we see how the lions fit in."
Among other areas of focus is an examination of the animals' diet, which is showing that closer to more dense areas of human habitation, a greater portion of their intake — as much as 20 percent — consists of smaller prey, such as raccoons, turkeys, skunks, as well as dogs and cats.
Heather Swanson, a wildlife ecologist for the city of Boulder Open Space and Mountain Parks, said the city's contribution to the study has been primarily in the area of logistical support.
"We know we do have a number of mountain lions at any given time" on city property, Swanson said. "There have been other studies (elsewhere), and while a lot of the research is applicable to our properties, having stuff that is collected locally, directly on our property, is of value to us in understanding our ecosystem, habitat management and recreation and everything in between."
Swanson said Boulder's participation underscores one more asset the city's expansive open space program provides.
"I think the lion study is the latest example, the (Parks and Wildlife) chronic wasting disease study being another, of what Open Space and Mountain Parks can present as a natural laboratory for the wildlife-urban interface and habitat.
"Boulder has the potential to offer a great laboratory for these studies, which can only be conducted in coordination with larger agencies such as DPW."
Genetic testing
Studying the lions' lives by necessity includes a look at how they die. Their human neighbors figure significantly in their mortality.
"Most of it is human-caused. Either road kill or management-related," Alldredge said. "It's lions killing livestock, lions interacting with humans, killing pets or being in the city too much, so that they end up being euthanized. Over half the mortalities are related to humans, roadkill or human interactions."
In his remaining time on the study, Alldredge will be employing a new methodology in assessing the size of the population. Rather than using relatively invasive "mark-recapture" techniques such as equipping lions with radio collars or ear tags, he hopes to employ testing of what he calls "hair-snags," fur samples that can be obtained and tested to produce an animal's unique genetic identifier by genotype.
"And then you have to recapture these individuals to actually get the population estimate," he said. "You end up getting a ratio of marked to unmarked individuals."
Dave Hoerath is a wildlife biologist for Boulder County Parks & Open Space also involved in the project. He compared the county's contribution to that of the city — primarily providing what he termed a "canvas," through its properties, on which Parks and Wildlife can conduct its work.
Hoerath stressed the absence in our area of "negative interactions" — specifically, attacks by the powerful animals on humans — that the study has uncovered.
"Whether there's two lions or 22 or 222 lions, it doesn't matter," Hoerath said. "The lions are doing what they're supposed to do. They're pretty much being where they're supposed to be, and they're eating what they're supposed to eat."
He said public reaction to David Baron's book "The Beast in the Garden: A Modern Parable of Man and Nature," which explored the sometimes-uneasy dynamics surrounding human coexistence with one of nature's most intriguing predators, also provided some initiative for the current study.
When researchers finally do publish a population estimate, Hoerath said, "A number might just scare somebody. But the data shouldn't scare you.
"The data says you shouldn't be scared."