Mild winter means deer fawn and elk calf survival looks good as we enter spring

Statewide winter survival for mule deer fawns and elk calves fitted with tracking collars has shown to be higher than average through the end of February.

“Right now (in mid-March) things are looking promising for both deer and elk,” Fish and Game’s Deer and Elk Coordinator Toby Boudreau said. “We’ll know for sure what survival will look like in the coming month and a half after we’ve tallied up the final numbers. But this is exactly what we were hoping for — back-to-back mild winters to help get herd numbers, specifically in southeast Idaho, back on track.”

A glimpse into winter survival

To monitor herds, Fish and Game biologists in early winter captured and collared 188 mule deer fawns and 75 elk calves across 14 different units to track their survival over winter.

Winter survival is typically the biggest single factor affecting mule deer herds, and the long-term average is about 60% of fawns surviving their first winter, but that percentage can drop significantly during hard winters.

By the end of February, 89% of collared fawns and 99% of collared calves were still alive, and here's how that compares with recent years:

• 89% fawns and 99% calves in 2025-26
• 78% fawns and 95% calves in 2024-25
• 92% fawns and 95% calves in 2023-24
• 72% fawns and 92% calves in 2022-23
• 84% fawns and 92% calves in 2021-22
• 83% fawns and 92% calves in 2020-21

This year’s winter (if you can even call it that) has been one of the mildest winters in decades, which may be bad news if you’re a skier or dried-out lodgepole pine in the month of July. But if you’re a deer or elk, it’s Easy Street — at least for now.

Not out of the woods yet

Depending on weather, March and April are often when fawn and calf mortality reaches its peak because the young animals' fat reserves are largely depleted and their digestive systems need time to convert to digesting fresh, green forage.

While many people associate a “hard winter” with deep snow and frigid temperatures, spring weather is also critical to survival. For mule deer fawns in particular, a stretch of cold, wet weather in the early spring can substantially drop survival, and biologists can see winter-related mortality as late as May. So while things are tracking well, it’s no guarantee the current crop of fawns and calves will continue on their current trajectory.

Why it all matters

Fawn and calf survival is critical to growing herds or sustaining current populations. Survival of young mule deer has a direct relation to the fall deer harvest because yearling bucks typically make up a significant portion of the overall mule deer harvest.

In addition to that, knowing how many collared animals die each winter gives our wildlife biologists a good estimate of how the rest of the population is faring. And knowing just how many animals — in this case, deer and elk — are out on the landscape is crucial when it comes to setting seasons and providing hunting opportunities.

For more information on this topic and other deer and elk information, go to Fish and Game’s State of Deer and Elk webpage. We’ve put together a robust series of 12 videos that highlight everything you’ve ever wanted to know about deer and elk, including why surveying matters to why/when Fish and Game step in to feed wintering herds.