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.” 

A fawn mule deer beds near the highway near Dubois in December 2021. (Mike Koshmrl/WyoFile)

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.

Full suite of species

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. 

A group of wild horses investigate a human intruder in southwest Wyoming’s Little Mountain area in spring 2023. (Mike Koshmrl/WyoFile)

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. 

University of Wyoming researchers found that average proximity to elk on mule deer summer range can influence fat gain by about 2%. (University of Wyoming)

“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.” 

Swings of things

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.”

The Red Creek Badlands in southwestern Wyoming’s Little Mountain area, pictured, includes an 8,020-acre wilderness study area. (Mike Koshmrl/WyoFile)

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, there 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.” 

Spring green up belies Little Mountain’s typical dryness. (Steven Brutger)

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.  

Trial management

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.” 

A deer hunter glasses for game on the flanks of Little Mountain. (Steven Brutger)

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.”  

Mike Koshmrl reports on Wyoming's wildlife and natural resources. Prior to joining WyoFile, he spent nearly a decade covering the Greater Yellowstone Ecosystem’s wild places and creatures for the Jackson...

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  1. The opposition to collaring horses shows that liberals, as well as conservatives, throw science under the bus when it doesn’t support their ideology.

  2. I grew up in Encampment in the 50’s and 60’s It was easy to more than a hundred deer on any given outing, several hundred during the winter. You could spend days looking for elk and never see one. Now the opposite is almost the case. Yes elk are grazers but when feed is hard to come by they browse taking away feed from deer. Also good feed areas with both grazing and browse will be shared by deer and elk. I and friends have observed in these areas if deer are feeding and elk show up the deer will move to the fringes or leave altogether. This observation was made in the Encampment River wilderness area, and in Savage Run wilderness area, both prime habitat for deer and elk. We have watched the elk win and deer lose in both areas and it didn’t take a million dollar study to know you can’t have both.

  3. Study area needs to be devoid of livestock grazing to show direct correlation; good luck with that in WY. To have successful wildlife population, WY needs to stop managing them for profit like livestock.

  4. Is it possible that elk population is on increase due to more wolves have been killed in 2021-2023. Wolves prefer Elk to dear when the pack size is normal. If the wolf pack size is less than 6 member, it is difficult to prey on large animals, also there is not need for a large kill so they would prey on easier prey, the dear. If the wild land were not managed by human, killing apex predators, the balanced ecosystem will be achieved naturally with biodiversity.

  5. All research needs to be taken in the context of the setting and its limitation. Comparing the low elevation low precipitation areas species dynamics between deer and elk with differing habitats with those in montane higher precipitation areas and drawing a conclusion that elk eat mule deer is a misapplication of the research. Case in point the Sierra Madre elk herd peak at estimated population between 12-14,000 around 2010-2014, the WGFD has been actively reducing the heard down to 6000+/- currently. In the corresponding years we have not seen corresponding increases in mule deer a 50% reduction in elk number has not translated to more mule deer. Habitat, anthropogenic impacts, predators, drought and bad winters and CWD are likely bigger drivers to mule deer population in the Seirra Madres than elk.
    Its rare in biological/ecological systems that single cause and effect relationships exist, they tend to be a little more complex.

  6. My question is did the elk take over the habitat and run the deer off, or has the habitat changed to being better for elk and poorer for deer? If it’s the latter, killing off elk will not bring the deer back.

    1. It seems obvious that the problem is that there is only just so much forage, to be shared by both species (and others).

  7. Have researchers speculated on actual elk-muley dynamics? Do elk passively out eat deer or aggressively push deer from food sources? Do elk take over essential cover, leaving deer to the elements?

  8. Wonderful research! This is something many of us have suspected for a long time. I’ve personally seen elk chase mule deer up and over mountaintops.
    More research is vitally needed in determining the impacts that feral domestic horses and other domestic livestock have on wildlife populations in areas like the Red Desert.

  9. Thank you, Wyofile for informing us about the deep scientific-political issues involved with Wyoming wildife populations, especially these key species.

  10. Wondering if cloud seeding has anything to do with the amount western Wyoming has received

  11. On the other end of the herbivore spectrum , I wonder about the overlap between wild ungulates and domestic livestock on available habitat.
    Keep in mind that one AUM of livestock on a grazing allotment of public land is equivocated to the feed needed for 2.5 cow elk or 4+ doe deer. ( an AUM is quantified as one cattle steer, a cow plus calf , or five domestic sheep and is the unit used by both the Forest Service and the BLM range managers ).
    If deer and elk ” compete” with one another for a finite food resource, do not both also compete with livestock in season? I question if the agencies have the spine to ever favor the needs of native wildlife first over the summer grazing allotments for cattle and sheep in rationing out the resource. Oh if only the herders paid a fair market value for their graze on public lands. The $ 1.35 per AUM grazing fee is the same dollar price as it was in 1934 when the Taylor Grazing Act attempted to get control of public land back from the avaricious cattle barons and sheep kings.
    No matter what decade you examine , the needs of migratory native wildlife have always been marginalized . Just know that Climate Change will adjudicate for all the stakeholders in the Supreme Court of Natural law , with deference to none.

    1. Typical blatter Dewey with your anti livestock rants. Your biology does not work. Mule deer are primarily browsers and cattle are grazers and elk do both. So a cattle AUM is like comparing apples and bananas to a deer AUM.

  12. Management of one of my favorite areas comes to my mind. The Sierra Madre / Sand Hills area is so interconnected I do not know how you would manage for single species. I want both to have healthy numbers there, if possible.
    The area has become one of the prime elk hunting ones in the state but, it has not always been that way. Back in the 60s and 70s I remember huge deer numbers. We were allowed more than one several years. As the elk multiplied, that changed. I don’t blame it all on larger elk numbers, and I am not a biologist, but I have hunted since the sixties there. I have observed and shared for years what I was seeing. They may not eat the same forage, but I think elk are simply big bullies around the deer and perhaps they simply take over?
    The Sand Hills has been one of the premier deer hunting areas for years, but at certain times elk use it a great deal too. While hunting pressure moves elk out of the the low country temporarily, I don’t know how you would keep them separated year around.
    It seems to me that we have been trying to knock the elk numbers down to objective for a long time. This winter has not helped the ratio.

  13. Observationally, over the last 30+ years I have noted that when elk move into an area, mule deer move out.

    1. The buck brush in trout and gooseberry canyons are now grass after the fires. I think type of food that the deer like have been replaced over the last 40 years.