Mule deer fawn and calf elk survival rates trending lower in Idaho

Winter survival rates for Idaho’s mule deer fawns and elk calves isn’t that great based upon February’s numbers. Currently, 72% of fawns and 92% of calves with tracking collars have survived, which is slightly below average for the most part, according to the Idaho Department of Fish and Game (IDFG).

“From an overview perspective, winter survival is tracking about average to a little below average from what we’ve seen in the past two years,” said Toby Boudreau, IDFG’s Deer and Elk Coordinator. “But, in the southeast part of the state, where winters have been long and severe, it’s not looking too good.”

The state is currently monitoring 182 mule deer fawns and 149 elk calves. Here’s how the current survival percentages compare to prior years:

With more snow than average across most of the state, biologists are also monitoring adult mule deer and elk survival rates, noting that most are doing well though mature animals tend to have a higher survival rate than younger ones. 

“We’re seeing pretty decent survival rates right now in our adult deer populations,” said Boudreau.

March and April are when fawn and calf mortality often increases as their fat reserves deplete and their digestive systems “need time to convert to digesting fresh, green forage,” according to IDFG. Right now, it’s too early to tell whether mortality rates will be higher than normal.

“It’s been a really hard year on our southeastern herds,” said Boudreau. “As of March 9, the southeast portion of the state is at roughly 145% of its typical snowpack. Critical deer and elk wintering ranges — including Portneuf, Montpelier, Georgetown Summit and Blackfoot WMAs — have been hit hard by this year’s winter weather, and with no certainty when temperatures will start to climb again, it’s not looking good.”

And, in Unit 69 near Idaho Falls, 43% of the mule deer fawns have died and 67% didn’t survive the winter in Unit 76.

“We’d like to see more mediated temperatures,” said Boudreau. “But at this rate, it’s going to take a few years for this year’s herd to rebound.”