Are state actions increasing the risk of cougars attacking people?

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Mark Elbroch/Panthera

The three cougar attacks on people in Colorado this year have made headlines around the world. This reflects not only how rare such attacks are, but also how unusual it is to have so many in one state in such a short period of time. The first occurred near Fort Collins in February, the second occurred near Kremmling in August and the third, and most recent, occurred near Bailey last month. The first two attacks were on adult men, while the latter was on an 8-year-old boy playing in his backyard. Young cougars were responsible for each of these attacks, a fact that may hold clues as to why these incidents have happened this year. 

Research suggests that young, especially male, cougars are more likely to have conflicts with people. Research also demonstrates that hunting cougars or thinning their numbers as a method of wildlife management can actually increase the number of young male cats on the landscape. Considering all three cougars involved in these attacks were young and two of them males (the other was eaten by scavengers to the point its gender couldn’t be determined), it raises the question: Is cougar hunting and/or wildlife management practices in Colorado actually increasing the risk for cougar attacks on humans? And, if so, who knows, and what are they doing about it?

The possibility that hunting cougars can lead to increased attacks on people has been known for some time. According to the book Cougar Management Guidelines, published in 2005, “Sport hunting [of cougars] is occasionally proposed as a tool to reduce the risk that cougars will attack humans. There is no scientific evidence that sport hunting achieves this goal… hunting may shift cougar population structure toward young animals, which are more likely than adult cougars to attack humans.”

The working group that created the guidelines was comprised of 13 professionals including two Colorado biologists with the Colorado Division of Wildlife, the forerunner of today’s Colorado Division of Parks and Wildlife (CPW.) 

Immediately preceding the aforementioned statement in the Guidelines it is noted that, “Sport hunting [of cougars] to benefit wild ungulate [aka big game] populations is not supported by the scientific literature… Any effort to control cougars should be part of an effort that addresses all factors impacting the ungulate population.” 

CPW’s controversial Piceance Basin and Upper Arkansas River Predator Control Plans, approved in December 2016 by the Parks and Wildlife Commission, called for the killing of cougars and black bears in an effort to increase mule deer populations (Boulder Weekly has reported on these controversial plans extensively in its “Off Target” series.) At least some of the body of research suggesting that increased cougar hunting leads to increased cougar-human conflict was included in CPW’s literature review for these plans. A significant portion of such research, however, was omitted. And that may prove significant in light of the recent attacks.


Mark Elbroch/Panthera

Implementation of the Upper Arkansas River Predator Control Plan has included killing a significant number of cougars in an area only 25-30 miles from where the young boy was recently attacked in Bailey. This proximity at least raises the possibility that there could be a connection between killing cougars in the Upper Arkansas River plan area and the attack on the boy. Dr. Robert Wielgus found during his research as director of the large carnivore laboratory at Washington State University that, “the areas where problems occurred — bad encounters [between cougars and people] … were the heavily hunted areas.” Wielgus says they didn’t see those types of things in areas where there was less hunting. When asked if he thought the killing of cougars as part of the Upper Arkansas River plan, which aimed to kill approximately 50% of the cougar population in one area less than 30 miles south of Bailey, could be linked to the attack on the boy, Wielgus responded, “Yeah, I do.” 

The Cougar Management Guidelines appear to agree with a subsequent research paper published by David Mattson, Kenneth Logan and Linda Sweanor, entitled, “Factors governing risk of cougar attacks on humans.” The study looked at 386 instances of cougar-human contact and found that “young cougars in poor condition are more likely than other cougars to threaten people.” 

 The study adds, “There is evidence that densities of young, dispersing cougars are likely to be comparatively high where local densities of resident adults have been depressed by hunting, as long as other nearby and less-heavily exploited areas serve as sources of dispersers. Under such a scenario, heavy localized hunting of older cougars could increase rather than reduce exposure of people to close-threatening encounters with cougars.”  

CPW’s literature review for its two aforementioned predator control plans doesn’t mention this aspect of the Cougar Management Guidelines nor the research paper by Mattson, Logan and Sweanor. 

And it’s not just human attacks that are potentially increasing due to the harvesting of cougars. According to a 2013 study titled “Effects of remedial sport hunting on cougar complaints and livestock depredations,” researchers found, “The odds of increased complaints and livestock depredations increased dramatically (36% to 240%) with increased cougar harvest. … We suggest that increased young male immigration, social disruption of cougar populations, and associated changes in space use by cougars … caused by increased hunting resulted in the increased complaints and livestock depredations.” 

While CPW did include this 2013 research in its literature review for its aforementioned predator control plans, it asserted that the researcher’s findings are not fully supported by data. 

Wielgus, who is a coauthor of the aforementioned 2013 study, says over a 20-year-period, he and his team collared hundreds of cougars throughout Washington state, and compared where there was cougar-human conflict and where there wasn’t. 

“At the time, the thought was, ‘Well, there’s too many cougars, and this super-abundance of cougars is causing increased conflicts with humans,’” Wielgus says. “But surprisingly what we found was that there wasn’t a super abundance of cougars, and it just appeared to be the case.”

Wielgus says this is because when hunters were killing large numbers of resident cougars, “particularly older dominant territorial animals, like hunters typically select for,” other cougars would come in to take their place. “One of our favorite sayings — it was the truth — when you kill one older dominant male, three younger guys come to the funeral,” he says.

Wielgus says that those older cougars don’t typically become old by having conflicts with people. So when these younger cougars would come in and vie for the older cougar’s former territory, they’d be more aggressive, “and you end up with three times as many cats as what you started with, except they’re young animals that are prone to get into trouble,” he says. “[W]hat we found was that this social disruption and killing the cougars was actually causing the problem.

 “Our findings, and the findings of other scientists that have actually studied it, are not very popular with many state fish and game agencies because it runs counter to belief,” Wielgus says.

He compares it to the findings of Galileo. “You come up with stuff and the powers that be don’t like it.”

Wielgus thinks the status-quo thinking of state agencies leads to a kind of treadmill, where more and more cougars are killed with the belief this will decrease conflict. “You kill more, and then immigrants come in, and then you kill more, and immigrants come in, until such a time when the population then collapses, but you wouldn’t see it, because the complaints and everything are increasing and increasing and increasing, until the female component of the population is wiped out, and then the cougar population collapses,” he says. 

Following their research in Washington, Wielgus says the state lowered the cougar hunting harvest rate to 12%, and he says, “all these problems have basically disappeared.”  

“And so over-harvest is what’s causing the problem,” Wielgus says. “I have no doubt in my mind that the attacks and so on that you’re seeing in Colorado are a direct result of over-harvest of cougars.” 

These findings appear similar to those of a 2016 research study by Kristine J. Teichman, et al., titled “Hunting as a management tool? Cougar-human conflict is positively related to trophy hunting.” In this study the researchers used “a 30-year data set on human-caused cougar … kills in British Columbia, Canada,” and found that, “Individuals that were killed via conflict with humans were younger than hunted cougars. 

“Accounting for human density and habitat productivity,” researchers continued in the study, “human hunting pressure during or before the year of conflict comprised the most important variables. Both were associated with increased male cougar-human conflict.”

CPW cites this study in the literature it reviewed for the Upper Arkansas River plan this way: “Although only providing correlative evidence, such patterns over large geographic and temporal scales suggest that alternative approaches to conflict mitigation might yield more effective outcomes for humans as well as cougar populations and the individuals within populations.” 

In response to the correlative — rather than causative — nature of the study, Dr. Mark Elbroch, lead scientist in the Puma Program with the conservation group Panthera says, “As every good scientist is taught their first day of school, correlation is not causation. In defense of Teichman, when you’re looking at 30 years of data across a massive area, yes it’s correlation, but my god, that is one really, really strong pattern. 

“It’s certainly the strongest of all these studies, in my opinion, in helping bridge the gap to causation,” Elbroch says, “But it is still a gap, and so it’s easy for the skeptic, who is also a scientist, to continue to point at that gap and say, ‘It’s not a direct causation.’”

Elbroch claims this is because researchers have never done the work necessary “to see the direct link between hunting and either increased risk to humans or increased risk to livestock. It just doesn’t exist.” 

But this may be for a good reason.

“Can you imagine that research?” Elbroch asks. “It would be so controversial,” suggesting researchers would have to tell the public they were going to increase cougar hunting to see if they could link it to cougars killing livestock or attacking people.

“No one would want to take the risk of actually making that link in the first place,” he says. 

In 2017, Elbroch published research in the journal Science, which he says looked at the social structure of cougars; how they share food, who they share it with, and how food moves through the community of cougars. He says the research described an interesting pattern: “larger [cougar] populations can no longer be thought of as gray masses,” he says. “They’re instead a mosaic of individual communities, and each community is governed by a territorial male. … The whole structure was based on the territory of these males.” 

Consistent with previous research, Elbroch’s paper states, “Trophy hunting of carnivores may also increase human-carnivore conflict and disrupt a species’ socio-spatial organization.” Elbroch’s paper makes a potential analog to grizzly bear, stating they can “suffer social disruption for up to two years following the selective hunting of mature males in the population. … Similar social disruption has been suggested for pumas under heavy pressure from trophy hunting,” the study states.

Elbroch says his research using social network analysis, “which is fairly new to wildlife research, provides interesting insights and is the ideal way to test disruption to mountain lion communities caused by hunting.” 

As mentioned, the area near Bailey where the 8-year-old boy was attacked is to the north of CPW’s Upper Arkansas River plan area by about 25-30 miles. In its write-up for the plan, apparently referring to the aforementioned studies — at least the ones it included — CPW states, “There is also the perception that high immigration rates of sub-adult males will lead to increases in human conflict and livestock depredation. Some studies have indicated that harvest and subsequent increases in sub-adult males have correlated with human-cougar conflict. However, others have found that demographic class did not relate to human-cougar interaction. This management experiment will provide direct information on human-cougar interactions with respect to changes in cougar populations, age structure, and immigration rates.”  

So CPW admits that its “management experiment” in the Upper Arkansas River plan area will provide information on “human-cougar interactions.” Are these interactions, which include attacks on humans, really something that should be part of a CPW experiment considering there is already a fair amount of research indicating attacks could likely increase as a result of killing more cougars? And shouldn’t the public have been warned that this experiment was being undertaken since their welfare seems to have been part of the experiment? 

More recently, the CPW biologist leading the Upper Arkansas River plan published findings appearing to affirm some of the very correlations he and others previously deemed to be only “perception.” In a study published in April by Mat Alldredge, CPW carnivore wildlife researcher, et al., titled “Human-Cougar interactions in the wildland-urban interface of Colorado’s Front Range,” researchers found that cougars were able to live in wildland-urban environments “with minimal human-cougar interactions,” which the researchers conclude “suggests that maintaining older age structures, especially females, and providing a matrix of habitats, including large connected open-space areas, would be beneficial to cougars and effectively reduce the potential for conflict.” 

Elbroch says what is,“meant by having an older age class and more females… is reducing the hunt and reducing female harvest.” 

Similar criticisms of the predator control plans were waged against CPW by conservation groups in a letter prior to the approval of the plans in December 2016: “[K]illing mountain lions to reduce complaints and livestock depredations can have the opposite effect. When the stable adult mountain lions are removed from a population, the disruption causes social chaos in their society. … The loss of adults encourages subadult males, naturally less skilled at hunting, to immigrate, and studies show that this influx is likely to be involved in human and livestock conflicts as well as causes increased infanticide on mountain lion kittens.” 

A close examination of the first cougar attack in Colorado this year, which occurred on Horsetooth Moutain, a part of Larimer County Open Space near Fort Collins, parallels the recent attack on the young boy in Bailey, and it appears to show that senior CPW officials may have been aware that cougar hunting could have played a role in the Fort Collins attack. It also appears to show the agency intentionally worked to keep discussion of such matters concealed from the public.

On Feb. 4, on Larimer County Open Space — in the middle of Colorado’s winter cougar-hunting season — a man was trail-running when he was approached and attacked by what was later determined to be a 3-4 month old, 35-40 pound, cougar kitten. The man bludgeoned the kitten in the head with a rock and choked it to death as it held onto his hand with its jaws. The kitten’s two young siblings were found nearby in the following days, trapped by wildlife officials, and placed into wildlife rehabilitation centers, according to CPW.  

In response to international media attention, CPW held a press conference to disclose details of the attack. According to emails obtained via an open records request, a senior CPW official instructed CPW staff coordinating the media event to avoid discussion about the potential of the kittens’ mother not being sighted, especially questions suggesting it might have been killed by a hunter. “They may ask a question about the numbers of lions in Colorado, hunting of lions etc. They may want us to speculate on why we didn’t see any sign of the mother and I don’t think we want to get into that discussion,” said Mark Leslie, CPW Northeast Region Manager. “I’m hoping they don’t get too far in the weeds with the questions, but if I was in their shoes, I might want to know some of these,” he wrote. 

But despite wanting to keep reporters from asking those questions publicly, CPW was asking them internally. In preparation for the press conference, a CPW biologist prepared a map for Leslie and a CPW public information officer with the locations of all the cougars known to have been killed in the vicinity of the attack in the months prior to the attack, both male and female. So, it appears CPW was considering both the possibility that the kittens’ mother had been killed by hunters or killed for attacking livestock, or the young cougars moved into the area because a male cougar was killed for the same reasons. 

CPW public information officer Rebecca Ferrell responded in an email that CPW has, “no conclusive evidence of why these three young mountain lions were found in an area with no adult female presence. The only thing we can say with certainty is just that — the young mountain lions involved in/found near the Horsetooth Mountain attack were alone, and we had no evidence of an adult female. This could be for any number of reasons, including death, abandonment or simply ranging away from her young — all of these potential reasons were offered at the time of the attack, but we have no conclusive evidence of any of them being the reason no female was found in the area. That is why we chose not to focus on questions about the mother — we simply do not and cannot know the answer.”

Further circumstantial evidence seems to indicate CPW was aware of the potential for increased conflict with people by the killing of adult female cougars. For each of the females that had been killed in the Horsetooth area — potential mothers of the cat involved in the attack — straight lines were drawn with the mileage from the kill site to the attack site on the map CPW had prepared just in case reporters asked the right questions. All three kill sites were between 15-20 miles away. The sites of males killed, both by hunters and for attacking livestock, are more numerous, and also exist well within a cougar’s range of the attack site. 

In Colorado, CPW uses cougar hunting as a management tool, both to maintain estimated population levels and mitigate conflicts with people and domestic livestock.

Both female and male cougars can be hunted during two different seasons, which essentially combine into one long season beginning Nov. 18 and ending April 30 of the following year. This means cougars can be hunted over five months out of the year. And all can agree that it can be difficult to tell female and male cougars apart at the distances from which most hunters are taking their shot, usually when the cougar is high up in a tree looking down, while dogs are baying at them.

Although mountain lions can give birth year-round, “in the Rockies they exhibit a ‘birth pulse’ and most are born in summer or early fall,” according to Elbroch. It is illegal to kill female mountain lions with kittens. “The absence of kittens with a lion does not mean it is a male or an unbred adult female,” according to CPW’s mountain lion hunting brochure. “Research has shown that young are close to their mothers about half the time.” This fact makes it nearly impossible for a hunter to know with any certainty if they are illegally targeting a mother cougar with kittens. 

Elbroch served as coauthor on a paper with Connor O’Malley that, based upon their findings, suggests delaying the start date of cougar hunting season until Dec. 1 of each year. This delay would avoid 91% of a cougars’ denning period, according to Elbroch and O’Malley. “Our research provides information to guide managers in aligning hunting seasons to mitigate orphaning kittens when they are youngest and most vulnerable, and provide hunters the best opportunities to detect and protect dependent young,” the study states.  

In 2018 alone, CPW killed 26 cougars as part of its Upper Arkansas River plan. Another 18 were killed in 2016 and 15 more in 2017. Again, this management unit is only 25-30 miles from where the attack on the boy in Bailey occurred.  

In the Game Management Units encapsulating Bailey, 14 cougars were killed in 2017-2018, including six males and eight females. 

When asked whether the agency believed the heavy harvest of cougars as part of the Upper Arkansas River plan increased the risk to public safety, CPW responded, “For the last three years harvest has been at or below historical quota levels. So we would not call this a ‘heavy harvest.’ Based on historical data, and the fact that human-lion interactions remain extremely rare, we have no reason to believe that risk was created or even escalated.”

This, despite CPW’s own description in its management plan, which states, “This management experiment will provide direct information on human-cougar interactions with respect to changes in cougar populations, age structure, and immigration rates.” 

Further, the important term CPW uses is “historical quota levels.” Between 1993-2003, the average kill rate of cougars relative to the quota was only 32% in the Upper Arkansas River plan area. 

After the cougar attack on the boy in Bailey, officials from USDA-APHIS-Wildlife Services killed two young male cougars nearby in the following days after they were reported eating domestic goats. DNA testing by the University of Wyoming forensics laboratory confirmed that one of the cougars was the one who attacked the boy, and was approximately 12 months old, according to CPW.

According to CPW documents, all cougars captured and killed as part of the Upper Arkansas River plan had genetic samples collected, presumably for future DNA analysis. Similar material was also taken and analyzed from the cougar who attacked the boy in Bailey, confirming the attacking cougar had actually been the one killed. In order to definitively determine whether or not the hunting of cougars in the Upper Arkansas River plan contributed to the attack on the boy, CPW should test the two sets of DNA material to see if there is any match, and release the results to the public.