Column: How do animals survive winter in northern Minnesota?

BEMIDJI, Minn. -- As any resident of the great white north will tell you, winters in Minnesota are no joke.

We all experience winter in different ways, some enjoy spending a lot of time outside; ice fishing, skiing, snowmobiling, and so forth. Others like to find cozy, indoor activities for those chillier five or so months of the year.

Being that we are humans and all, we have the wonderful luxury of having these choices laid before us as the seasons change. Meanwhile, the creatures that roam the woods (and our yards) have no such luxury.

This thought has crossed my mind a lot since moving into the city of Bemidji a couple of years ago. Primarily because of the insane amount of gray squirrels that occupy our little plot of land, which also happens to be in close proximity to several fast-food chains the critters like to frequent. Well, their dumpsters at least.

These fluffy little creatures never seem to mind one bit when it’s freezing out or there’s three feet of snow on the ground.

This led me to ponder my main question: how on earth do squirrels survive winter?

That question put me on a search to see how a variety of animals, both big and small, are able to not only survive, but thrive in this frigid wasteland we call northern Minnesota.

I started my research like any millennial would: on Google. I found some answers on the Department of Natural Resources website and got the basic responses one would think, but I wasn’t satisfied. So, I reached out to Blane Klemek, an outdoors columnist for the Bemidji Pioneer. I figured as a wildlife manager with the Minnesota DNR, he probably had a good deal of insight on the topic. And boy was I right.

According to Klemek, there are around five species of squirrel in the state of Minnesota: the fox squirrel, red squirrel, the southern flying squirrel, and the northern flying squirrel. But gray squirrels are probably the most common of them all.

“The four requirements for wildlife -- any wildlife, including us -- is space, shelter, water and food,” Klemek said. “And with those four things together, wildlife can flourish and survive and reproduce.”

The obvious fact, considering they spend winter days scampering around my yard, is that these little guys don’t hibernate like their close relatives the woodchuck and chipmunk do.

“No tree squirrel hibernates. And so how they adapt would be behaviorally,” Klemek said. “And the things they do is -- just like any animal would, including us -- you seek shelter in inclement weather.”

One of the places they find this shelter is in bushy nests made out of leaves, which can often be seen up high in the branches of trees. These nests are called drays. For a dray to provide shelter and warmth during harsher winter months, squirrels will harden and thicken their drays by adding more layers of leaves, twigs and moss.

Klemek said they will also readily use the cavities of trees, abandoned woodpecker holes or things like artificial nest boxes. “They'll fill them full of leaves or soft grass-type material, but mostly leaves, and they'll crawl into those things either singly or a couple, three squirrels to huddle in and get warm and share each other's body heat,” he said.

Another way squirrels have adapted is in their food caching abilities.

“They'll, you know, collect nuts -- acorns for example -- and bury them,” Klemek said. “And they have pretty good spatial memories. They all do, in remembering where they bury these things. And they'll dig through the snow to get at those caches of nuts and other food items. And they'll cache them for later consumption.”

A fun fact I found on the DNR website is that a gray squirrel can hide 25 nuts in half an hour and can later find roughly 80% of what it buried.

“It's a cycle. It's a life cycle. And it's different with each time of year and in different seasons," Klemek said.

He explained that around January and February is when squirrels typically will have a strong drive to reproduce and begin breeding, with babies coming around March or April.

Once the snow begins to melt, that is when they finish off their food stores and restore fat reserves that were lost over the course of winter. As the summer goes on, there's more food being produced out there such as nuts, seeds, fruits, etc. for them to collect.

Then at the onset of late summer and early fall is when they begin to harvest and are in the thick of their caching activities and nest building. They need to eat more during this time to put on some fat before winter sets in. And hopefully once wintertime comes, they're set.

“Unless Mother Nature didn't cooperate,” Klemek said. “I mean, that happens all the time where, you know, maybe it's a dry droughty year and nothing is being produced. Well, that's when you will see a population decline. And that ebbs and flows, too, with the abundance of the resource.

“It’s a crap shoot out there for these creatures. You prepare the best you can. But if Mother Nature doesn't cooperate, then it's hard times.”

After our thorough discussion about squirrels, Klemek and we talked about an assortment of creatures that have to work extra hard to survive the harsh winters.

Unique body features and changes in physiology and behavior help bald eagles maximize energy gain, minimize energy loss, and incubate eggs in cold temperatures. To maximize gain, eagles forage in groups, gorge on food, and increase the assimilation of ingested food energy. To minimize loss, they become sedentary, seek protective microclimates, and reduce night-time body temperature. Put simply, eagles keep warm by using the least amount of energy to get the most amount of food. They also stay close to rivers that remain open all year, such as the Mississippi River, in order to have access to food.

Deep snow and winters of 100 or more days can cause hardship for deer. Gradual reduction in daylight hours triggers changes in the deer’s metabolism and coincides with lower availability of green and growing food sources. They enter a period of semi-fasting that results in lower food needs. Whitetails eat dormant vegetation and buds of a variety of shrubs and young trees during the winter. The hair in a deer’s winter coat is hollow like a straw. The air that fills each hair is heated by the animal’s body, acting like an electric blanket.

Snowshoe hares are dark brown in summer, but when winter comes they grow an entirely new coat that is as white as the snow around it. Their hind legs are also noticeably larger, and have more fur and larger toes than those of other rabbits or hares. This provides additional surface area and support for walking on snow. In winter they eat slender twigs, buds and bark. They have also been known to nibble on the frozen carcasses of other animals and sometimes eat their own droppings, which provide them with extra nutrition. In bad weather, they will stay under the covering of thick brush or bushes to stay warm and dry.

In addition to adding a thicker coat in the winter, one thing that chickadees are able to do is lower their body temperature at night , going into a state known as hypothermia. They also use shivering as a way to generate heat while they are sleeping, however this uses up their fat reserves. So, they typically start each winter day finding sources of fat to lay on enough to get them through the coming day and especially the night ahead. They often spend the night in a tight-fitting roost hole where the surrounding wood gives them some insulation from the nighttime temperatures.

During winter, red foxes grow longer coats that cover them up to their footpads to help them in keeping warm. Unlike their pups, adult foxes do not stay in their dens to keep warm. Instead, they curl into a ball in the open and even sometimes blanketed in snow. They are also known to dig burrows in the snow to escape harsh temperatures. In the winter their coats change from gray or red to white to blend in with the frozen habitat. The coat is thicker with more rounded hairs to insulate the heat and keep the foxes warm. The fur on their tail grows thicker in the winter and they wrap it around their body at night to help insulate heat.

Beavers put on body fat during the fall, providing insulation as well as stored energy to help them in the winter . In particular, a beaver’s tail is designed to store fat and shrinks in size over the winter as the fat is used up. Thick fur also insulates a beaver from the cold. As it grooms, it spreads oil from anal glands over its fur, waterproofing its coat and so it can swim without getting its body wet. They live in shelters called lodges, which they spend the entire winter inside of. In the fall, they store food in the water around their lodges. In the winter, they will swim out of the lodge to get food under the ice.