DULUTH — Northeastern Minnesota's deer are entering a critical period, a live-or-die time of year as they wait for deep snow to melt and something green to eat to sprout in the woods.
Some of them will likely die waiting.
The winter severity index used by the Minnesota Department of Natural Resources already has reached the severe category for large swaths of Carlton, St. Louis, Lake and Cook counties (areas of black on the map). Those are the areas where winter impacts are likely to increase deer mortality above the usual 10%.
Other areas are rapidly approaching severe (areas of purple on the map) and, unless the snowpack melts very quickly, likely will hit the severe level soon. This week's snowstorm likely will push even more areas into the black.
As the News Tribune noted in early March, the biggest culprit of winter is deep snow. The winter severity index awards a point for every day with 15 or more inches of snow on the ground and another point for every day it gets below zero.
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Deer can withstand cold just fine, if they can move around easily to find shelter, food and escape wolves. But in some areas deer have been wading through three feet or more of snow for most of the winter.
And it’s not just deer that die outright that continues to keep the Arrowhead region deer herd down. Female deer that survive winter in severe areas are likely to give birth to just one fawn, or none at all, instead of the usual twins, a factor that will hold the regional population down for years to come.
While a melty March can often bring relief to the northern deer herd, this year it was crueler than most, with ongoing snow and cold. April appears to be trending cold and snowy as well, with little sign of a rapid warmup and melt that would bring relief.
Deer really won’t start to recover until green-up occurs in the woods, likely sometime in May.
“It has been a tough winter and I think we can assume we will lose some deer,” said Chris Balzer, DNR wildlife manager in the Cloquet/Duluth area. “It would really help if spring would come soon. Every extra week of these conditions can make a difference in deer survival.”
The super-snowy winter continues a decade-long trend. It’s now the seventh of the last 11 winters, and four of the past five, that have soared into the severe range for large parts of the region, out-snowing even the worst winters of the 1960s and '70s.
Moreover, as the snowpack melts a little and then refreezes each night, a hard crust forms that allows wolves and other predators to run on top while deer often still punch through, making deer even more susceptible to predation.
All of this will mean continued and even expanded bucks-only deer hunting this fall with likely reduced antlerless permits in other areas.
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The good news is that deer numbers can rebound fast if given a string of several mild or even normal winters in a row. That happened after several brutal winters in the 1990s, when a string of very mild winters in the early 2000s led to all-time record-high deer numbers, even as wolves also thrived.
Forest habitat is also a big issue, and the low-calorie food available across much of the Arrowhead — namely browse like aspen twigs — isn't great for helping deer survive tough winters. Wildlife experts note that areas with agricultural fields offer a quicker snowmelt and faster green-up in spring and will allow more deer to survive even severe winters compared to heavily forested areas.
Across North America, white-tailed deer thrive best when they have forest near farms. In the far north, deer also need stands thick confer for winter cover, so-called deer yards, which have been declining in many areas.
Agricultural fields offer deer food later into the fall and the snow tends to melt faster in open areas, offering food sooner in the spring.
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