With snow still covering the landscape in the North Woods and a late-arriving spring, there are concerns about the severity of the winter on wildlife.

While the winter started slowly with limited snow in December and January, recording-breaking snow amounts fell in February raising the concern for wildlife, especially deer, turkeys and grouse.

Michele Woodford, De­partment of Natural Re­sources (DNR) wildlife biologist in Woodruff, said for the most part deer are in good health at this point with no reports of high mortality in deer yards.

“We would like for people to submit reports of any issues in deer yards (three or more dead deer in a single location, for example, would be a red flag),” said Woodford. “I’ve not heard of any die-offs. We’ve been out to check on a few dead deer and so far have not found anything unusual for this time of year. 

“The results are what we expect to see during moderate and severe winters — fawns have the least amount of stored fat (they spent their summer growing instead of putting on extra fat) and some will starve,” said Woodford. “Old deer have their own challenges. A deer that was found showing starvation signs this week was over 12 years old, her teeth were worn, some missing or decrepit. She had food in her belly.”

Woodford said assessments done so far this year show deer to be in better condition than they were at this same date last year.

“This is not entirely unexpected,” she said. “December 2018 and January 2019 were very mild in terms of snow depths and deer are specialists at conserving energy during cold weather.”

This winter, the big snowfalls didn’t arrive until February, when more than 60 inches fell in parts of the North Woods. There are currently about 14 to 16 inches of snow in the woods.

“This year, we had very deep snow depths but for a relatively short period of time,” said Woodford. “Two dead deer were assessed south of Woodruff (away from town) last week. One was a buck in great condition with lots of fat. The 4- to 5-year-old doe still had rump fat. Rump fats and fat stored outside of the muscles are the first fat stores to be used by deer during the winter. We found no deer with rump fat last year (even near subdivisions).” 



Winter severity

Woodford and other state wildlife biologists can use the winter severity index (WSI) to compare the impact of the weather on wildlife.

The WSI is calculated by adding the number of days with a snow depth of at least 18 inches to the number of days when the minimum temperatures were below zero. The WSI points accumulate during the winter, allowing DNR wildlife experts the ability to compare the severity of the winter from year to year. 

A WSI of 49 or less is considered mild, 50 to 70 is moderate, 80 to 99 is severe and 100 or greater is very severe.

The total WSI for Eagle River as of March 31 was approximately 90 points (49 snow and 41 temp points combined) 

With the recent warmer weather, the snow depths have dropped dramatically from about 36 inches in the middle of March. 

Woodford said cold nights provide a snow crust that allows grouse and turkeys to walk on it.

“This gave them some reprise and the ability to find additional places to forage. Animals will modify their activity periods to take advantage of crusts. I saw deer using the south-facing slopes where snow is beginning to melt below evergreen trees and bare patches of grass are showing here and there,” according to Woodford. “April will be the critical month to watch.”

Woodruff said population estimate models are using winter severity (and the rates of mortality based on the index) to calculate prehunt 2019 herd estimates.

“For example, we plugged in a winter severity index of 90 points for Vilas even though when the model was set up, actual WSI (through February) was only at about 50 points when the models were run,” said Woodford.



Some fish kills


The thick ice and deep snow on lakes also could result in some fish kills, according to Steve Gilbert, Woodruff Area fisheries supervisor for the DNR’s Bureau of Fisheries Management.

“I assume that the lakes that historically have winterkills will have issues again this year,” said Gilbert. “ Our staff have visited several of these waters to check dissolved oxygen levels this winter and will continue to do so. Most of our natural lakes should be fine. The main factor will be when the snow starts to melt and ice eventually goes off our waters. Lakes with aeration systems should be just fine as long as they remain running until the ice goes out.”

Gilbert said people that suspect that a winterkill has occurred on a lake should contact the local biologist so that they can follow up on the report.