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Serving Northern St. Louis County, Minnesota

Deer WSI on the rise

Marshall Helmberger
Posted 2/23/22

REGIONAL— After an exceptionally mild start, the region’s winter severity index, or WSI, for whitetail deer is rising quickly and could be headed for a moderate-to-somewhat severe rating …

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Deer WSI on the rise

Posted

REGIONAL— After an exceptionally mild start, the region’s winter severity index, or WSI, for whitetail deer is rising quickly and could be headed for a moderate-to-somewhat severe rating depending on the weather over the next several weeks.
As of Wednesday, the WSI stood at anywhere from 85-to-110 across the region, with the variation depending mostly on snow depth. The WSI, which wildlife managers use as a guide to winter deer mortality, adds a point for every day with a below zero temperature and another for every day with a snow depth of 15 inches or greater.
With weeks of subzero temperatures and snow depths around the area now in excess of 24 inches across most the region, the index has added points most quickly in February, as snow depths in most locations reached the 15-inch threshold. And with several days of subzero temperatures in the forecast through next Monday, WSI readings could reach the 95-125 range by this time next week. At this time last year, the WSI stood well below 50, in one of the mildest winters in years. Winters with a total WSI value of 50 or lower are considered mild, according to the DNR. Winters ith readings of 51 to 119 are considered moderate, while winters topping a reading of 120 are considered severe, although readings that high are not unusual in northern St. Louis County.
DNR wildlife managers acknowledge that the WSI is only one of a number of factors that impact deer survival. The overall duration of winter and the timing of spring green-up, along with the quantity and quality of habitat and forage, are other factors that affect survival. Wolf density and food competition from other deer can make a difference as well.