Winter Hits Mule Deer Fawns And Does Especially Hard

May 26, 2017

Credit Tom Koerner/USFWS

Researchers studying mule deer in the Wyoming Range in western Wyoming say that all the fawns they radio-collared last year died in this year's harsh winter and that 40 percent of the female does also perished. University of Wyoming wildlife biologist Kevin Montieth said usually only 15 percent of does die in winterkills. 

Montieth said many deer are still on their winter range eating sagebrush, instead of the green grasses they'd normally have access to by now. In some of their habitat, mule deer were dealing with snow levels up to 200 percent of average and died of malnutrition because they could not paw down to more nutritious food. 

“What we saw this year is smaller size the offspring growing within these individual females, suggesting that such poor nutritional condition is even suppressing growth of fetuses that moms are carrying,” he said.

Some of the herd is well known for its 150-mile migration to its summer range near Hoback Junction. Montieth said the Wyoming Range mule deer population had been steadily growing but it's likely to take several years for the herd to rebound. He says the herd still hasn't recovered from a similar winterkill back in 1991. 

Montieth is part of the Wyoming Range Mule Deer Project that has been documenting the steady growth of the herd until now. He said all that data will come in handy in learning whether mule deer can recover from winterkills like this one.

“Before this winter our intentions for the Wyoming Range Mule Deer Project was to do our work for one more year,” he said. “Now with this winter, our aim is to look beyond that and understand what it looks like for recovery for this deer population.

Montieth added, on the bright side, the high mortality means there will be fewer mouths for the habitat to feed this summer, giving the deer that do survive a good chance of putting on weight before the next winter hits.