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This year's mild winter largely beneficial for fish and wildlife species

Feb. 3—The winter of 2023-24 with its unseasonably mild temperatures and lack of snow has been a bust for outdoor recreation of many kinds, but it's mostly beneficial for fish and wildlife after consecutive harsh winters the previous two years, natural resource managers in North Dakota and northwest Minnesota say.

"There's winners and there's some losers, but mostly with resident wildlife, it's on the winning side of the equation," said Blane Klemek, Northwest Region wildlife manager for the Minnesota Department of Natural Resources in Bemidji. "The past couple of winters were hard on deer, of course, and deer right now, throughout, I'd say all of Minnesota, are doing just fine and able to access food. And in some parts of the state, I would not doubt at all that deer are actually putting on fat.

"They're able to get all kinds of food."

The story's similar in North Dakota. Last year, winter came early and stayed late, deep snow blanketed most of the state, and brutal temperatures were the norm. The deep snow covered food supplies for many wildlife species, and the extreme temperatures quickly depleted any fat reserves that remained.

The conditions were especially hard on deer and pronghorns, said Bill Haase, assistant wildlife chief for the North Dakota Game and Fish Department in Bismarck.

"From a wildlife standpoint, we were really hoping for an easy winter this year," Haase said. "Another winter like that would have been pretty devastating."

Despite last winter's harsh conditions, upland game birds did surprisingly well, Haase said, as did bighorn sheep and elk.

For a while this past fall, it appeared the region was in for a repeat of 2022-23, when winter began in November and lingered well into April.

That, however, turned out to not be the case.

"We did have that snowstorm in late October and I was thinking, 'Oh boy, this isn't good,'" Haase said. "Some of the deer started to go into farmyards already, but luckily, we had the warm spell before deer season and all the snow was gone, for the most part, before deer season."

Since then, aside from the ice storm that hit much of the state after Christmas, conditions have been unseasonably tame.

"It's been a much better winter than last year, that's for sure," Haase said. "We did get that ice storm a few weeks ago and that was a fairly substantial accumulation of ice in the southeast, but luckily, it was followed by mild weather, so that was good."

Deer aren't the only species to benefit from benign winters. Conditions remain favorable for upland game birds, as well, even though the bare ground doesn't offer shelter for snow-roosting birds such as ruffed grouse and prairie grouse.

"They all utilize snow for snow-roosting and they haven't necessarily needed to do that this year," the DNR's Klemek said. "It hasn't been all that cold.

"Those species of birds are doing well. They're able to access food and get around no problem."

Same with wild turkeys, Klemek said, which are a relative newcomer to northwest Minnesota.

"They're everywhere now — everywhere in the state," he said. "I don't think there's a county in the state that doesn't have wild turkeys. They're another species that cold doesn't get them, it's the depth of snow. Just like deer, if the snow's too deep, they can't access food and get around as well. That's when you'll see mortality in turkeys, but a mild winter like this year, turkeys are doing much better than they did the last couple of winters."

There have also been fewer complaints of critters such as deer and turkeys getting into farmers' hay and other feed supplies.

"It's pretty minimal — almost no complaints," Haase said. "Last year, our staff were extremely busy. They didn't have enough time to do a lot of their other job duties. They had to prioritize the depredation work, and so this year, they're able to catch up and get some of those other job duties done that were neglected last year."

One of the most striking examples of the difference between this winter and last is the Winter Severity Index, a measure the Minnesota DNR uses to gauge the impact of winter on deer. To calculate the WSI, 1 point is accumulated each day the air temperature is 0 degrees F or colder, with an additional point added for each day with at least 15 inches of snow on the ground.

By winter's end, an index of 120 points or higher indicates a severe winter, while an index of 50 or less reflects a mild winter.

Last year, a large swath of northeast Minnesota and parts of northwest Minnesota were in the severe category by winter's end. This year, by comparison, the entire state was in the "mild" category as of Jan. 24.

"It's not a perfect system, but we haven't been gaining any points," Klemek said. "We did have a few days below zero, but even then it wasn't all that bad."

The only wildlife that might be losers during winters such as this are predators such as gray wolves and coyotes, he said.

"Not to the point where it would impact the population as a whole, but wolves aren't able to capture deer quite as easily during winters like this," Klemek said. "They do their best, as far as capturing and killing prey like deer, when winters are long and the snows are deep and deer have a hard time getting around.

"They have a little bit harder time capturing prey in winters like this."

From a management standpoint, the lack of snow also is a setback for aerial deer surveys in North Dakota and — potentially — the annual winter elk survey in northwest Minnesota. North Dakota to date hasn't been able to fly any of its winter deer surveys, Haase said, which it traditionally uses to help set license numbers for the next hunting season.

"If we do get over a foot of snow across the level in any units, we will fly them, and we'll be ready to go immediately," he said. "But otherwise, at this point, we're not able to fly any deer surveys. But you know what? That's all right this year — we'll take that. That's OK."

The department was able to fly its elk surveys in western North Dakota, though, Haase said.

"We were still able to fly those without snow," he said. "We're in the midst of completing those right now."

In northwest Minnesota, by comparison, snow is crucial for spotting elk on the forested landscape in the DNR's survey area.

"The desirable snow conditions aren't out there," Klemek said. "We'll continue to watch for windows of opportunity through the end of February to conduct it. Survey protocol calls for at least 8 inches on the ground, and we're barely at that right now."

Without the survey, the DNR may have to be more conservative in allocating the once-in-a-lifetime elk tags in northwest Minnesota. The DNR didn't conduct a survey in the winter of 2021, either, because of the COVID-19 pandemic, which resulted in a slight reduction in tags, Klemek said.

"If we weren't able to actually do a survey this year, I would expect we would decrease the number of tags, but those decisions haven't been made yet," he said. "That's my sense."

From a fishing standpoint, the lack of thick ice and deep snow is a positive development — at least for the fish — because it reduces the chance of winterkill. Last winter, some 40 North Dakota lakes experienced at least some fish die-offs, and winterkill in about 30 lakes was significant, said Greg Power, fisheries chief for the North Dakota Game and Fish Department in Bismarck.

Winterkill occurs when heavy snow atop the ice reduces light penetration, preventing aquatic plants from producing oxygen through the process of photosynthesis. As plants die and decay, they further deplete dissolved oxygen levels to the point where fish can't survive.

This year, by comparison, is "totally a 180" from last winter, Power said.

"Conditions are scripted better for survival under the ice," he said. Lack of runoff could be an issue come spring, but at least there won't be back-to-back severe winters with significant winterkill.

"It's a double-edged sword, winter in North Dakota," Power said. "From a biologist perspective, you worry about winterkill, but then you also need that runoff. We always say the perfect-case scenario would be a winter like we've had and then just get dumped on in March and April — rain and snow."

Whether that happens — and what the rest of the winter holds — remains to be seen. But for now, at least, the winter of 2023-24 will go down as one for the record books.