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Winter severity index up but deer herd hanging in there

The Department of Natural Resources annual “winter severity index” for white-tailed deer in Northeastern Minnesota indicates 2004-2005 is above the long-term average. Temperatures have been about average, but snow depth is above normal. This was a return to the old fashion “real” winters the north woods are well known for.The DNR has conducted the “Winter Severity Index” (WSI) for the past 40 years to give us a statistical comparison between winters. The winter severity index (WSI) is measured by combining the number of days below zero with the number of days with 15" or more of snow. The WSI is recorded at DNR Wildlife offices throughout northern Minnesota. A “normal winter” in the Tower-Ely Area would end up around 125 WSI points. The index for winter 2004-05 is at 146 (Temp Days=67, Snow days=79), as of Monday, March 21 at Tower, and 115 (Temp days=46, Snow days =71) at Eveleth. Wildlife managers continue to monitor deer populations as the winter progresses. “We expect increased deer mortality due to winter (and wolves) as a result of a winter greater than 125 points,” said DNR wildlife manager Tom Rusch. “Deer mortality has been mostly limited to fawns and yearlings up to this point.”The current snow conditions swing the balance in favor of predators. Wolf kills are being found in most areas. Deer are shifting to south-facing aspects and other areas with less snow, where it is available within winter cover, to improve mobility and find browse.In general, deer are well adapted to tough winters. Young deer are genetically adapted to handle about 3 months of deep snow and bitter cold. After that, the fawns start to run out of fat reserves and starve or are killed by wolves and other predators. They are the most expendable part of the herd.Adult buck mortality increases with a WSI greater than 140. According to the DNR, very little adult buck mortality has been observed as of mid-March. Adult does are the best prepared to survive harsh winters and suffer the least mortality. This is nature’s way to ensure survival of the fittest and rebuild the herd.The winter of 1995-96, the toughest on record, was 202 at Tower/Ely and 160 at Eveleth. Last winter the WSI was 152. The most extreme winters start early (December) and run late. Northern St Louis County did not receive heavy snow until mid-January this winter. Research indicates snow depth is the most critical factor for white-tailed deer in Minnesota. How March and April play out will determine how our deer fare this winter. If deep snow hangs on well into April, we will lose a lot more deer than if it breaks by the end of March.

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