Winter Severity Index up from last year
By Sam Cook
Duluth News Tribune
Yes, it's cold.
And, yes, the snow is deep.
But so far, this hasn't been a severe winter, at least not by standards that matter to white-tailed deer.
Biologists in both Minnesota and Wisconsin keep a Winter Severity Index to track the progress of winter. We're having a snowier and colder winter than last year. But to date, it's been nothing like the severe winter of 1995-96.
"The main difference this year is that we had reached the 15-inch threshold for snow in December. Normally, we don't do that until January," said Mark Lenarz, leader of the Forest Wildlife Populations and Research Group for the Minnesota Department of Natural Resources in Grand Rapids.
Under Minnesota's Winter Severity Index, one point is accrued each day the snow depth is greater than 15 inches and an-other point is accrued for each day with a low temperature of zero or below.
The highest index reading in Northeastern Minnesota as of Monday was at Snowbank Lake near Ely, with 48. That repre-sents 23 "snow" days and 25 "temperature" days, Lenarz said. That 48 compares to 31 last year at the same time. In the win-ter of 1995-96, however, Ely had recorded a Winter Severity Index of 58 by this time.
Some locations, such as Cloquet, have almost identical readings to last winter.
Deer are having no problems getting around, Lenarz said.
"I expect that up in the Arrowhead country, deer are having a more difficult time getting around, but they were able to get into wintering yards," Lenarz said. "The snow did not occur in one fell swoop. As the snow begins to accumulate, deer move to their winter range. There was time for them to make that shift."
Deer are doing fine so far in Wisconsin as well, said Fred Strand, DNR wildlife biologist in Superior.
"It's still early in terms of impact to the deer," Strand said, "but if the weather we've had in December continues a couple more months, it could have an impact."
The WSI reading at Brule was 18 at the end of December, compared to 12 in December 2007. Barnes was at 14, compared to 9 in December 2007. At Mercer, the reading was 19, compared to 15 in December 2007.
Deer are adapted well to living with cold temperatures, Strand said. It's deep snow that causes them the most trouble.
Last winter was considered moderate by severity standards in Wisconsin. But data gained since then indicates it was a bit harsher than biologists had thought, Strand said.
The past summer's data on ratio of fawns to adults showed fewer fawns than biologists had expected. Gun deer season harvest data showed fewer fawns and yearlings were taken than biologists expected, Strand said. That indicates there was lower fawn production last summer and less survival of fawns during the 2007-2008 winter than expected, he said.
"Last winter probably had more effect on deer than we thought based on the WSI," Strand said.