Thriving elk, struggling deer: Coincidence? New research suggests not

By Mike Koshmrl,
Posted 4/24/23

“More is not always better,” University of Wyoming ecology professor Kevin Monteith told WyoFile. “In this situation, with deer and elk, we may not be able to have our cake and eat it too. We may not be able to have robust, large populations of elk and robust, large populations of deer.”

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Thriving elk, struggling deer: Coincidence? New research suggests not


Findings emerging from an intensive, years-long Wyoming research project are beginning to substantiate suspicions that elk may be thriving on western landscapes at the expense of widely struggling mule deer.  

“More is not always better,” University of Wyoming ecology professor Kevin Monteith told WyoFile. “In this situation, with deer and elk, we may not be able to have our cake and eat it too. We may not be able to have robust, large populations of elk and robust, large populations of deer.” 

Monteith’s remarks reflect preliminary data out of this lab that show a distinct inverse correlation between the amount of body fat female muleys gain during the summertime and their proximity to elk. In other words, the closer deer live to elk, the skinnier they get on average. And not just by a little bit. The difference measured out to about two percentage points of fat gain — which can make the difference between life and death. 

“How fat animals are plays a pretty key role in their survival,” Monteith said. “Two percentage points of body fat in autumn could influence overwinter survival by 10%. For an adult female, that’s a pretty big deal.” 

And for a mule deer herd it’s a big deal, too. Even a 5% downward swing in overwinter survival among female deer, Monteith said, can have a “legitimate effect on a population.”

Many of the findings aren’t yet published, but the science is far enough along that the Wyoming Game and Fish Department is acting on it, and is in the process of identifying areas to knock down elk numbers in hopes of helping deer.   

Wildlife managers and big game hunters have long suspected an interplay on the range between elk and mule deer, two native ungulate species trending in the opposite directions.

In Wyoming and beyond, bigger-bodied, adaptable elk are on the upswing, with populations stretching above objectives to record levels and the species is thriving in developed areas and varied landscapes, even in places where they’re not welcomed.  

It’s the doldrums, meanwhile, for mule deer, a species that’s less able to cope with disturbances. In Wyoming the population has fallen from 500,000 mule deer around the turn of the century down to around 300,000 today, and numbers are poised to slip further yet in the wake of a winter that’s decimating some herds. 

The two trajectories are part of what motivated the Rock Springs-based Muley Fanatics Foundation to invest more than $1 million into the Deer-Elk Ecology Research project — AKA, the DEER project — some seven years ago. 

Although the title of the project suggests a narrow scope, that’s far from the case. Monteith, his partners, postdoctoral fellows and students conducted a holistic ecological examination of how mule deer use the landscape and are influenced by elk, coyotes and mountain lions. They also set out to understand how mule deer interface with wild horses, though that effort was shut down by federal officials.

“Politically, [collaring horses] became an impossibility,” Monteith said.

The work took place in the Greater Little Mountain area, a roughly 1.5-million-acre swath of southwestern Wyoming east of Flaming Gorge Reservoir. The landscape there transitions from sagebrush-studded grasslands in the valleys to patches of pinyon, juniper and aspen trees at the mid-elevations and subalpine fir along the 8,000 to 9,000-foot-high crown of the region.

The project area was chosen because it’s representative of a high-desert system where mule deer have struggled and elk thrived, Monteith said. Human causes of mule deer decline, like energy development, he said, are also minimal around Little Mountain.

“It’s a fairly pristine environment,” Monteith said, “with an intact predator assemblage.” 

Field work stretched from 2016 to 2019, when Monteith and his colleagues captured and GPS-collared 76 doe mule deer, 35 cow elk, 33 coyotes and six mountain lions. 

The Little Mountain region is home to the South Rock Springs Elk Herd, last assessed slightly above its population objective. A mule deer herd of the same name lives there, too, though is well below its population objective.  

Data from GPS collars were collected by researchers years ago, but the most exhaustive study about deer-elk competition is still a work in progress. There are complex questions, Monteith said, at the heart of the equation.

“The reality is there are still a whole series of things that we continue to work on,” Monteith said. “Science moves slower than we all want it to, both from the perspective of collecting data and then pulling all the pieces together.” 

But some answers and peer-reviewed papers from the Little Mountain research have started to come through, including about how, counterintuitively, deer select for risky habitat associated with elk and predators. Research has also been published from the DEER project highlighting how coyotes seem to have limited ability to avoid mountain lions, a hard-to-detect ambush predator. 

Monteith has said in public forums he’s “confident enough” in the preliminary findings about elk-deer competition to risk publicizing conclusions that could still change. Speaking at a Wyoming Wildlife Taskforce meeting a year ago, he presented a graph that illustrated the correlation between fat gain and elk proximity.

“This looks like a shotgun blast — don’t worry about that,” Monteith said. “What’s underneath the hood is a model that’s accounting for whether or not females recruited young, how old they were, what they experienced on their summer range, etc.” 

“It’s certainly very convincing evidence,” he said, “that there’s potential competition between deer and elk.”  

To Muley Fanatics Foundation co-founder Josh Coursey, the preliminary DEER project findings confirmed a longstanding suspicion: That increasing elk numbers have played a role in mule deer decline.

“Elk just have so much more flexibility and resilience to be able to survive on the landscape, and deer just do not,” Coursey said. “That landscape made for the perfect laboratory for that study, and I think that information can be used and applied across the West — not just in that small ecosystem.” 

Others want to see Monteith and his postdoc’s final analysis before they make up their minds. 

“One question I have is, ‘What habitats are the deer living in that are potentially close to elk?’” Wyoming Game and Fish Department biologist Patrick Burke said. “Is it basically not good deer habitat and better elk habitat? Is that why they have lower body fat, or is it from something else? Because that’s a possibility.”

Burke is the biologist whose district covers Little Mountain and the South Rock Springs elk and mule deer herds. Although elk in the region are overpopulated, and the deer far below their objective numbers, their respective rise and fall haven’t exactly lined up, he said. 

“Elk numbers have been fairly consistent, and have actually decreased a little bit during the time that mule deer decreased,” Burke said. “There’s times in the past, like the ‘90s, where the elk population was actually a little higher than it is now.” 

The South Rock Springs Mule Deer Herd has “never really been at objective,” Burke said. On paper the state calls for 8,500 animals, and at last assessment there were just 2,600 — nearly 70% under the goal. 

“I don’t know if [8,500] is attainable,” he said. 

The objective, Burke said, stems from a “political desire from the public to have more deer.” 

Little Mountain is not an especially productive habitat for mule deer, Burke said. Ratios of fawns-to-does — which signal whether the population is shrinking, stagnant or growing — tend to be on the lower side, in the thirties and forties per 100, which is often “not enough to maintain the population,” he said.

“We have lower fawn ratios following dry summers,” Burke said. “It’s different from your typical herd, like in the Wyoming Range, where they have access to high-elevation summer country. Down here we have a lot of winter range but very limited summer range, and it’s also pretty dry country.”

Even if the science isn’t yet cemented, state wildlife managers intend to hunt down elk populations in places to see if mule deer respond.

“We’ve got enough information from the work Kevin’s done to this point,” Game and Fish Director Brian Nesvik said during a March 2022 meeting. “We can feel very comfortable doing some pilot work to see if making prescriptions and adjustments with all the species in the system can actually have some effects on the ground.” 

Other pilot projects intended to help mule deer will target predators like black bears and mountain lions.  

More than a year later, the state agency has yet to implement elk-reduction plans explicitly for the purpose of easing pressure on mule deer. 

“We haven’t initiated any experimental pilot projects,” said Embere Hall, Game and Fish’s science, research and analytical support unit supervisor. “What we’ve done, so far, is try to capitalize on opportunities where elk are over objective, to bring them back towards objective.” 

That practice, of using hunting to trim herds, is standard wildlife management. 

Hall emphasized that the rise of elk and fall of mule deer is a “correlation, not a causation” outside of the Little Mountain area. But there are plenty of areas in Wyoming where the larger cervids are especially thriving while the smaller species languishes. The Laramie Mountains are one example, she said. 

Wyoming’s ongoing Mule Deer Monitoring Project, a 5-year project that has GPS-collared 1,000 animals in five focal herds, could help inform where the elk-reduction pilot projects take place, Hall said. 

Coursey, who provided funding that got Monteith’s DEER project off the ground, said that in his opinion there’s an obvious place to test out slashing elk numbers: Little Mountain.

“There’s so many factors why that made for such a good laboratory,” he said. “It’s limited quota for three elk areas and one prized deer area, with very little development. I think that’s the perfect place to start.”

The concept might not have traction with all stakeholders.

“That’s a very popular elk hunting area as well,” Game and Fish’s Burke said. 

Although Monteith’s conclusions aren’t yet ironclad, the idea that interspecies competition contributes to mule deer’s challenges has been gaining popularity with the support of the new science. Sy Gilliland, president of the Wyoming Outfitters and Guides Association, presented the point as fact this week as he argued for keeping all of Wyoming’s controversial elk feedgrounds going. 

“If we turn those elk loose and they close feedgrounds, they will find those mule deer winter ranges,” Gilliland told the Wyoming Game and Fish Commission on Tuesday. “And we know what happens when elk compete on the landscape with mule deer — mule deer lose every time.”