“Be careful what you wish for” is familiar advice. Those of us who welcome a good old fashioned snowstorm had our wish granted just after Christmas. Snowfall totals for that event in Central and Northern Minnesota ranged upwards of 10 to 15 inches, even more in some places. The counterpoint to its picturesque Currier-and-Ives effects was the challenge of difficult driving conditions, and mega snow removal in the aftermath. But to that subset of Minnesotans who call themselves “snow lover,” it was something to both revel in and take in stride, and left no doubt that the transition to winter is complete.
Over much of the state there is already as much or more snow than accumulated in the winter of 2020-2021. The post-Christmas snowstorm was not the first, so the above numbers can in many places be bumped up by several inches. As this is being written the weather forecast is for still more snow. If you’re a retailer who sells snowblowers, snowmobiles, skis or snowshoes, this could be a banner winter!
But winter has more than one dimension, and by New Year’s Day that other familiar aspect—numbing cold—had also made an appearance. There was no need to travel to the counties along the Canadian border to find Arctic-like conditions. Even as far south as the geographical center of Minnesota, temperatures plummeted to as low as minus 30 degrees.
Wintry conditions can lead to very different things, not only for humans but also for our wildlife neighbors. Neighbors like whitetail deer, including the band of a half dozen or more that regularly amble across our property during pre-dawn, nighttime and evening hours. Snow and cold are not inevitably threatening to deer. But too much in combination can be.
Wildlife management agencies in the snowbelt states, like the Minnesota Department of Natural Resources (DNR) Section of Wildlife, use a yardstick—literally—to help them measure the severity of a winter for deer. Most wildlife managers call this a winter severity index, or WSI for short. The WSI involves a little math, combining snow depth and sub-zero temperature readings. Every day with an air temperature of zero or below is worth a point. Every day with a snow depth of 15 inches or greater is also worth a point. Together they add up to the WSI.
ADVERTISEMENT
The effect of sub-zero temperatures on deer and other wildlife needs little explanation. At such temperatures food consumed is burned up more rapidly to maintain body heat. As a result, available winter food supplies can be exhausted more rapidly, and more time must be spent feeding and exposed to the elements.
The effect of deep snow on deer is also well known. Travel between feeding and bedding areas becomes more difficult and energy consuming. Eventually snow depth may lead deer to “yard up” near a food supply in order to limit the need to travel. If deer remain confined like this long enough they may exhaust their food supply, become weakened and either starve or be more susceptible to predation, most commonly from wolves.
Over the course of a winter the points for days of deep snow and the points for days of sub-zero temperature are tallied. Unlike basketball or football, this is a game where low score wins. Based on historical records and experience, wildlife managers have a pretty good idea what WSI score is likely to mean dire things for deer. This is especially true in the forested regions of Minnesota.
According to the Minnesota DNR, a WSI score of 50 or lower is considered a mild winter. Between 50 and 120 points is considered moderate. Above 120 is a severe winter. But even if deer do not succumb directly to winter-caused starvation, or to becoming easier targets for predators, they may emerge from winter in weakened condition. This in turn can lead to poor reproduction; meaning stillborn fawns or fawns born in weakened condition with poorer prospects of survival.
Last year, the winter of 2020-2021, was more lamb-like than lion—notwithstanding an extended February cold snap—with very low snow totals over much of Central and Northern Minnesota. Cold temperatures alone can be handled very well by the hardy whitetail. This year we’re starting out with snow depths that are at, or near, the depth at which the count begins. Those who care about our deer will be hoping that the lion of early winter will give way to the lamb sooner rather than later.
It’s also sometimes said that “it’s an ill wind that blows no good.” What might be bad for one may be good for another. Something that can be bad for deer—deep snow—can be a godsend for another creature that inhabits the same northern woodlands: the ruffed grouse. To many Minnesota upland bird hunters the ruffed grouse is the state’s premier game bird, no slight intended for the tenacious and colorful pheasant, or the ubiquitous wild turkey.
The deep snow that can impede the travels of whitetail deer makes a safe and snug burrow for the ruffed grouse. Under the snow the temperature rarely drops below 20 degrees above zero, though the open air above may be far colder. Leaving its snow burrow mostly just to feed on aspen buds or other forage, a ruffed grouse is far less available to predators—like hawks, owls or foxes—than if snow is sparse and the bird remains exposed for longer periods of time.
Winter’s blessings and curses affect other creatures, too. The pheasant does better with less snow to cover food supplies and fill up the cattail swamps where they find winter refuge. The snowshoe hare, with its large feet and thick and camouflaged winter coat, is perfectly adapted to deep snow and cold. The snowmobiler, the skier and the snowshoe trekker couldn’t be more delighted with snow in abundance, while the ice fisherman bemoans heavy snow before full ice depth, which can make a lake surface slushy and difficult to navigate.
ADVERTISEMENT
Not to mention those of us with septic systems that froze due to last winter’s sparse snows, but are now covered with a generous blanket of fluffy white insulation!
