This winter, so far, has been easy on Minnesota’s white-tailed deer population. With little snow on the ground and a warmer than normal January (despite the cold snaps), deer are doing just fine.
With the past weekend’s snows, snow depth in the woods is starting to add up. The Minnesota Department of Natural Resources keeps a Winter Severity Index, which helps biologists estimate how many deer will make it through a northern winter. Under the WSI system, one point is accrued each day the temperature drops below zero, and another point is added for each day the snow depth is greater than 15 inches. Until this last snowstorm, only temperature points had been accumulating. Now, though, the snow on the ground is more than 15 inches deep in many places.
Look here for the DNR’s latest WSI report. Scroll down the page to the” Winter Severity Index by Deer Permit Areas.”
And here are excerpts from an e-mail I received today from Tom Rusch, DNR area wildlife manager at Tower, discussing the winter severity:
“The winter of ‘12-‘13 has been mild for white-tailed deer up to this point,” Rusch wrote, “with the last WSI index at 31 on the Range on Feb. ( all of which were temperature points). This reading was made prior to the Feb. 10 snowstorm that dumped 8 inches on the Iron Range.
“December was very open with snow depths less than 6 inches. The first half of January continued to be very mild with temperatures as high as the upper 40’s and rain, which diminished snow cover. Temperatures plummeted in the latter half of January, but snow depths were still less than 15” at Tower and Eveleth through Feb. 8.
“Deer movement was not restricted. Deer were able to access food sources across their home ranges throughout December and January. Deer remained dispersed in fall cover until early February, when they shifted to better winter thermal cover with the wave of below zero cold that moved in. Snow depth is the key factor in deer survival in northern Minnesota.
“Snow depth surpassed the 15-inch threshold north of Orr in St. Louis County, and in northern Lake County, in late January. Snow depth surpassed 15 inches on the Iron Range on Feb. 10, but the next WSI report isn’t until Feb. 18. Snow points are now accumulating in each deer permit are in the Tower Area and will continue until snow depths again drop below 15 inches in March.
“Wolf predation, so far, has likely been very light, with deer having excellent mobility and wolves being at a disadvantage. Deep snow turns the tables and gives the advantage to wolves, especially as winter drags on.
“At this mid-winter juncture, I would predict this winter is going to end up below average (WSI=120 @ Tower). If that is indeed the scenario that plays out, the 2013 fawn crop would be the second consecutive bumper fawn crop in St. Louis County, with back to back mild winters. Consecutive large fawn crops historically have put population growth on the fast track. Time will tell, but the prospects for the northern Minnesota deer population appear to be on the rise. By March 1, we will have a firmer grasp of the effects this winter on our white-tailed deer population.”