With record snowfall across the Intermountain West, deer populations took a hard hit this winter—and it’s not over yet. From feeding plots in Utah to fawn mortality in Idaho and tag cuts in Wyoming, MeatEater dove into the numbers behind ungulate winterkill in three western states. This is what we found.
Utah has a diverse range of habitats—from the red-rock canyonlands of the South to the Wasatch Mountains of the North—and ungulate mortality this winter reflects those differences. Based on a deer-survival study involving over 1,000 GPS-collared animals, the state has a pretty good idea of what’s going on.
Utah DWR Big Game Coordinator Dax Mangus summed up the winter like this: “The Good: high deer survival and production in southern Utah; The Bad: lower fawn survival in central Utah; The Ugly: extreme fawn loss and pockets of high adult-doe mortality in far northern Utah.”
In terms of overall survival, Mangus reports 94% for elk, 81% for adult deer, 52% for fawns, and 90% for pronghorn, with higher mortality along the Wyoming-Utah border.
The Wasatch mountains were hit with their harshest winter since 1982, with ski resorts reporting upwards of 800 inches of snow this season. The snow came early, piled up high, and stayed late. According to Mangus, deer that wintered at higher elevations had very high fawn loss and above-average adult mortality. Deer that migrated to the east side of the range, wintering on the high-elevation plains tucked between the Wasatch mountains and the Wyoming border, didn’t fare all that much better.
In January, Utah implemented a deer feeding program at 11 locations in Rich County on the eastern flank of the Wasatch.
“In the areas where we're feeding, the vegetation that deer eat in the winter is completely covered by snow,” DWR Northern Region Wildlife Manager Jim Christensen said in a press release. At the feeding grounds, biologists are distributing specially-formulated pellets that have the nutritional value necessary for deer to survive.
Deer growth and survival in the more arid parts of the state like Zion, Bryce, and Moab, are typically limited by water, according to Mangus. But monsoon-pattern rains in the last two years have given deer populations a good boost, and the state is reporting record-high adult and fawn survival in these southern regions. In central areas, the winter was a mixed bag, with average adult survival but higher-than-normal fawn loss.
DWR is recommending a 25% cut (about 4,800 tags) in buck licenses on the worst-impacted units in northern Utah. In the central part of the state, they’re proposing to keep permit numbers similar to 2022 and even increase tag numbers 20 to 25% (about 3,000 tags) in southern areas. The Utah Wildlife Board is set to approve 2023 season tag numbers in a meeting on May 4.
Utah also implemented a state-wide shed hunting ban from February 7 until April 30. "In these types of conditions, big game animals are weakened and highly vulnerable to repeated human-caused disturbances," Utah Division of Wildlife Resources Director J. Shirley said. “Closing the shed antler and horn gathering season will minimize a major source of disturbance in the areas and during the time periods when big game animals are the most exposed and vulnerable.”
In Idaho, like Utah, the harsh winter was localized to specific parts of the state. The southeast corner from Island Park to the Utah border was hit particularly hard—not a huge area, but one of the most productive for mule deer in the state.
“We didn’t fare as bad as we could have,” according to IDFG Elk and Deer Coordinator Toby Boudreau. However, the agency has found that winter is one of the most limiting factors to deer growth, and this winter is likely to be no exception.
Boudreau reports that deer mortality in most hunting districts is tracking about on par with the average except for a few units in southeast Idaho. Based on deer radio-collar data, the state has already lost 94% of fawns in Unit 76 (based on a sample size of 30 collared fawns) and over 80% in other units south of Idaho Falls. In an average year, those numbers would hover closer to 50%.
Elk fared better than deer, with about 35% calf mortality so far this winter. That’s a little higher than the average 15%, but not high enough to cause alarm. According to Boudreau, elk have a longer digestive tract than deer proportional to their body size, allowing them to get more nutritional value out of the same forage. During harsh winters, when vegetation is scarce, that can mean the difference between life and death for ungulates.
With snowpack at over 200% of the long-term average in some parts of the state, we likely haven’t seen the final mortality numbers yet. There’s also likely to be a lag effect from this winter in terms of overall deer populations. In addition to missing a juvenile year class in heavily-hit areas, adult does will be at an energy deficit for months and might not bear fawns this coming year as a result.
Boudreau predicts that hunter success rates might be lower a few years down the road, but that success rates this upcoming season are unlikely to change much—most mortality is in juveniles rather than mature bucks.
After a succession of mild winters and good summer conditions from 2017 to 2022, wildlife managers proposed to increase buck tags and antlerless deer licenses this year. All those proposals were tabled in response to this winter. Tag numbers will not change much this year in Idaho as a result.
As preventative measures this winter, the Caribou-Targhee National Forest on the Idaho side of the Wyoming range extended all winter range closures to May 1. “Our wildlife will benefit from any relief we can provide them,” IDFG Regional Supervisor Matt Pieron said in a press release.
Wyoming is home to one of the largest annual ungulate migrations in North America, and it coincided with the heaviest-hit region of the state. Deer from the Wyoming Range on the Idaho-Wyoming border migrate nearly 200 miles south every winter into the Red Desert of Wyoming. Based on radio-collar data from Wyoming Game & Fish, 35% of mule deer does in the herd have perished thus far, along with 90% of yearling fawns.
Prior to this winter, the herd numbered around 30,000 animals. Aerial photographs taken from the winter range near High Savery Reservoir in the south-central part of the state show it completely covered with a thick blanket of snow. In a typical winter, the range is usually dry, sagebrush country. This year the area received 180% percent of the typical snowpack and over 60 days below zero.
The winter took a large toll on pronghorn populations in Wyoming as well. In Sublette County, south of Pinedale, Wyoming Game & Fish reports that 50% of adult female pronghorn have died this winter, mostly as a result of pneumonia. While pneumonia is not inherently lethal, harsh conditions and malnourishment have increased the mortality rate of infected individuals. Heading into this winter, pronghorn in the state were already suffering population losses from a summer outbreak of epizootic hemorrhagic disease—a virus that tends to spread in hot, dry summers, which Wyoming has experienced in recent years.
At a commission meeting last week, wildlife managers successfully proposed a decrease of 10,290 antelope licenses and 4,410 mule deer tags. Elk quotas, however, will be increased by 2,235 tags this year.
To protect wintering deer and elk along the Pinedale-Rock Springs migration corridor, wildlife managers proposed an emergency shed hunting closure last week. It was approved on the 25 and postponed the May 1 antler-hunting opener west of the Continental Divide to May 15.
Notably excluded from the closure, however, is Teton County—home of the infamous Jackson shed rush. Why exactly Teton County was excluded is unclear, considering Jackson Hole Mountain Resort set a new snowfall record of 595” this winter, and the foothills were still buried in snow as of this week.
Western hunters won’t experience the full impact of this winter for several years, but wildlife agencies are hoping the emergency measures they’re taking can soften the blow. Colorado and Montana have also taken steps to bolster their ungulate herds, and they’ll be tracking through the summer to see if additional actions are necessary.
Feature image via Wyoming Game & Fish.