Across state, winter’s been mild for deer
International Falls, Minn. — It’s unlikely Minnesota’s whitetails got the memo late last year that the weather phenomenon known as El Nino was expected to deliver above-average temperatures and below-average precipitation this winter. But they’re no doubt enjoying the benefits thus far of an accurate prediction.
As of early February, nearly the entire state was scoring a “winter severity index” below 50 points – with points scored for days zero or below zero, and those with a snow depth of at least 15 inches. Only small areas in the extreme northeast – areas subject to higher lake-effect snowfall totals – scored above 50. And not by much.
That’s not to say deer are out of the woods when it comes to dealing with winter.
“We usually don’t peak at snow depth until mid-March,” said Larry Petersen, DNR area wildlife supervisor in International Falls.
And, he adds, not all days with deep snow – which limits the ability of deer to move about and burns more energy when they do – are the same.
Deep snow can have less of an effect on deer early in the winter season than in April, as the metabolism of whitetails picks up and fawns are developing in does later on.
“Deep snow when (energy) demand is increasing is worse than having deep snow in January,” Petersen said.
But that, too, may or may not occur this year. For now, snow depth is moderate across most of Minnesota. And temperatures zero or below have been rare.
“Basically, we’ve accumulated a few (WSI) snow points in the northeast, but otherwise it’s just been cold weather (points),” said Steve Merchant, DNR wildlife populations and regulations program manager. “It’s really shaping up to be a mild winter.”
In the far north, WSI has more meaning that it does the farther one travels south. The north is colder, and heavy snow can limit the mobility of deer and increase the risk of predation from things like wolves. A mild winter means more deer survive, and increases the odds of a productive spring.
“It’s the kind of winter where there’s good overwinter survival,” Merchant said. “Does are healthy and have fawns that are healthy.”
Several parts of the state, including the International Falls area, are struggling to build the deer population. In fact, the past two years the DNR has limited the kill, by permit, of antlerless deer to build those numbers.
While the mild winter will help, Petersen said a subsequent mild winter would be an even greater boon to deer reproduction.
Right now, Petersen said, “There’s not a lot of does out there, relatively speaking.”
Had this winter (thus far) come along with twice the number of does on the landscape, the impact would’ve been substantially greater concerning reproduction.
“We need a good follow-up winter,” he said.
Those who track the recovery of the deer herd following harsh winters often point to the situation that arose in the mid-1990s.
It was during the winter of 1995-96 that the WSI in the International Falls area hit nearly 220 (180 generally is considered “severe”). The following winter (1996-97) was almost as bad. Fewer deer died that year, Petersen said studies showed, but that likely was because the weak of the herd had been cropped off the previous winter.
“Two punches” he called the winters’ effects on the deer herd in the north. A total deer harvest that a couple of years earlier was around 200,000 fell to about 143,000 in 1997 – the lowest total until a harvest of fewer than 140,000 in 2014 following cold and snowy winters.
The deer herd of the mid-1990s benefited from the fact that four of the next five winters were mild – below 50 on the WSI scale, Petersen said.
“That allowed the herd to recover quite fast,” he said.
To the contrary, five of the past 10 winters have produced WSIs of 150 or above at his I-Falls station. Only two winters have been below 50 points. This one has that potential.
That’s the kind of news that provides hope for deer hunters who’ve been dismayed in recent years by the number of deer they’ve seen while hunting.
“We’ve seen significant increases (in deer numbers following mild winters),” Merchant said. “We expect to see that this year.”
But WSI typically is tracked until May, if needed. That leaves a good chunk of winter ahead. Merchant, however, doesn’t expect dramatic change.
“Given the overall climate situation we’re in, I think it’s kind of hard to imagine that winter’s going to turn around and get kind of brutal,” he said. “That’s good news for deer.”
And for deer hunters. In much of the state, Merchant said, herd growth remains the goal.
“It’s not universal, but most areas want to see growth,” he said, referring to DNR and public goal-setting during the past couple of years.
Daylight lingers longer, and the sun’s rays strengthen, too, as March approaches, Dave Olfelt, DNR regional wildlife manager in Grand Rapids, points out.
All DNR wildlife supervisors in the northeast had reported this to be a moderate winter, Olfelt said.
But in the far northern reaches, winter’s just part of the equation.
“Winter can’t just stand alone,” Petersen said of what kills whitetails. Hunting pressure is relatively light, but wolves take a bite out of the deer population in the same way that winter does.
This winter, he said, “is certainly a step in the right direction.”