Wildlife in winter: It's been a tough one for Minnesota's critters

One of the longest, coldest, snowiest winters on record is nearing an end, and for most Minnesota wildlife, it can't come soon enough.

That critters large and small — from whitetail deer to tiny chickadees — can survive 30-below-zero temperatures, bitter 40 miles-per-hour winds and mountains of snow is nothing less than amazing. Even to wildlife biologists.

"You wonder how anything can survive,'' said Carrol Henderson, Department of Natural Resources nongame wildlife program supervisor. "It gives you great appreciation for the adaptability of wildlife. It's a real miracle.''

How do they do it?

Well, not all do.

Some deer, pheasants, turkeys, wolves, songbirds and other animals die each winter, for a variety of reasons. This winter likely has taken a higher toll, though no one really knows for certain. Animals die and are consumed, usually in obscurity.

"Winter mortality is a natural thing,'' said Steve Merchant, DNR wildlife program manager. "So people shouldn't be overly alarmed, because that's just the nature of the beast.''

But wildlife biologists say those efforts have little overall impact on wildlife populations. And Minnesota's animals are built to withstand Minnesota winters.

While wildlife officials aren't concerned yet about the overall effect of this winter on wildlife, lingering winter weather in March is a concern because many species are stressed. A late blizzard or ice storm can deal a coup de grâce.

"It's been a tough winter,'' Merchant said. "Not as bad as 1996-97, but it's close to that. And we could still have a lot of winter to go. This is really the crunch time now.''

Here's a look at how some critters are doing:

"Deer are designed for this,'' said Gino D'Angelo, DNR deer researcher in Madelia, Minn. "They have evolved to endure Minnesota winters. Otherwise we wouldn't have any.''

That fat near the skin "is like our Thinsulate,'' D'Angelo said.

Unlike some other animals, deer also slow their metabolism in the winter to conserve energy, meaning they don't eat as much. They burn the fat near their skin first, then the fat near their organs and finally, if stressed, the fat from their marrow.

D'Angelo said it's rare to see large numbers of deer starve to death. Young and old deer are usually the first to succumb. And weakened deer are more susceptible to predators, such as wolves and coyotes. But the longer the winter lasts, the more fat reserves they burn.

"As days tick on, it's like taking money out of your bank account. Eventually you get to a deficit,'' D'Angelo said.

Chickadees are among the smallest birds trying to survive winter.

"They go into tree cavities at night where they are better insulated from the cold,'' he said. They and other birds can puff out their feathers to increase insulation, "and they can pull one foot up into their feathers'' to stay warm, Henderson said.

Chickadees and other birds need constant food to provide energy, which exposes them to weather — and predators. They are common at back-yard feeders, but Henderson said a Pennsylvania study showed just 20 percent of chickadees' diet came from feeders.

"They are built for the cold,'' said Dan Stark, DNR wolf specialist. "They have that thick, heavy winter coat with a layer of underfur that insulates them.''

Their feet have denser tissue than domestic dogs, and on brutally cold days they simply curl up out of the wind, snuggling their nose under their fur.

They are one of the few animals that likely flourished this winter. "In extreme conditions, wolves have an advantage over their prey,'' Stark said. Deer, their primary food source, have been weakened while burning up fat reserves, making them more vulnerable. For wolves, that means good hunting.

Bald eagles can be spotted all winter long in some parts of Minnesota, especially along its rivers. "They are pretty hardy birds,'' Henderson said. They feed on dead deer or fish, or ducks, geese or small mammals. Golden eagles hunt squirrels and turkeys, Henderson said.

The reintroduction of turkeys around the state has been a wildlife success story, but the birds, while hardy, suffer in winter. Navigating deep snow on short legs is more of a problem than the cold.

"This is a tough year on turkeys, without a doubt,'' Merchant said. "They are pretty darn tough animals, but this deep snow isn't helping them.''

They need to feed regularly, and burning up energy just staying warm means they have to spend more time foraging and less time in the roost, conserving energy. Which makes them more vulnerable to predators, such as eagles and coyotes.

Some brave ducks, geese and trumpeter swans hang around pools of open water all winter, while most waterfowl migrate to warmer climes. Their down insulation allows them to weather the winter. Trumpeter swans are seen on open water near Monticello. "They are an incredibly hardy bird,'' Henderson said. "They have a couple inches of thick down that allows them to endure those incredibly cold days.''

Doug Smith • 612-673-7667

Twitter: @dougsmithstrib