Digging in for winter

Different mammals have different methods for surviving the coldest months


When the mercury plummets and the snow starts to fly, most forest creatures don’t head for the hills — they dig in for winter.

Some hibernate, sleeping for days on fat stored from summer. Some are partially dormant, sneaking outside on warmer winter days. And others are awake all winter long, withstanding all that Mother Nature dishes out.


A groundhog in grass.

(Photo by Anothony Schalk)

Woodchucks, for instance, go into a period of deep hibernation, usually between the months of October and February. The roly-poly rodents spend most of the summer eating plants in order to build up a layer of fat, up to one-half inch, by early fall. And it’s this girth that gets them through the winter.

During hibernation, a woodchuck’s body temperature drops to between 38 and 57 degrees, its heart beats at 1/10th the normal rate and breathing slows to about once every six minutes. Finally, sometime before March, the woodchuck emerges from its winter burrow and becomes active again.


A racoon poking its head out of a tree cavity.

(Photo courtesy of Bertrand Leclercq)

These critters, on the other hand, go into a partial hibernation either alone or in groups. During severe weather, they mostly sleep in their dens for days and weeks at a time, but they will venture out on warm winter days. Like woodchucks, raccoons gorge themselves during the summer, feasting on berries, acorns, crops and garden vegetables, especially corn.


A chipmunk in a snow-covered field.

(Photo via Shutterstock)

Chipmunks also are semi-dormant during the winter and their hibernation periods vary. Some chipmunks are dormant for long periods of time, some for short periods and others not at all. But chipmunks don’t have to put on heavy layers of fat for the winter because they stock their food chambers with nuts. 


A skunk in a snow-covered field.

(Photo via Shutterstock)

Skunks stay in their burrows and sleep for periods of time and occasionally become active on warm nights in the middle of winter. It is not unusual for one to 10 females to den together, sometimes with one male. 


An opossum walking through a snow-covered field.

(Photo by Darek Konopka)

Opossums prefer to stay on the move, but they will chill out in an underground winter den for 20-30 days during winter. They sometimes share their burrows with other animals such as skunks or woodchucks. As many other mammals do, they will line their dens with leaves or other soft material. During extreme periods of cold, they may even plug the entrance with leaves as extra protection against the elements. Even with these precautions, it is not unusual for opossums to be missing a part of their tails or ears from frostbite.

Gray Squirrels

A squirrel holding on to a tree limb.

(Photo by Chad Merda)

Gray squirrels stay busy in late summer and fall gorging on acorns, hickory nuts, walnuts and beechnuts. They also bury nuts in the ground for later use. They will dig a hole 3-4 inches deep, place the nut inside and use their nose to push it down. Then they will move dirt over the hole with their front paws, patting it down. Using their nose also may be a kind of scent marking that helps them locate the nut later in the season. They can bury up to 25 nuts in a half-hour. 

The red squirrel is similar to the gray squirrel in that neither one hibernates. Both are active during the middle of the day and both prefer tree holes for their dens. But red squirrels differ by storing more nuts than they can eat and adding white pine cones as a major part of their diet. Another difference is the red squirrel stores its food in caches instead of individually. 


A rabbit in a snow-covered field.

(Photo via Shutterstock)

Cottontail rabbits feed on the buds, twigs and bark of trees during winter. If they are lucky enough to find an abandoned orchard, they will dig through the snow to nibble on frozen apples. Many times, they eat snow for water. They are most active at dawn and especially dusk. They typically live in shallow depressions, called “forms,” in the ground that are 4-6 inches wide and 6-8 inches long. During severe conditions, cottontail rabbits may crash the entrance of another animal’s burrow or a natural cavity to stay warm. 

During winter, the meadow vole is one of the mainstay food items for red foxes. If heavy snow cover makes voles too difficult to find, the red fox will turn to rabbits, mice, moles and possible carrion, such as dead deer. Foxes often cache their food near trails, either in the snow or in the ground. They will excavate a hole using their feet, drop the food in, and cover it up with dirt using their noses. Red foxes undergo internal changes that pump more blood to their paws, ears, tail and nose to help them withstand extreme cold, and their fur becomes longer and thicker. 


A beaver along the shoreline.

(Photo via Shutterstock)

They are active during the winter, living in stream banks and lakes or in lodges made of tree branches, sticks, mud and stones. They construct great piles of small, tender branches nearby which serve as feed piles for the winter. Some of the branches are underwater so the beavers can have access to them when ice forms. 


A muskrat poking its head out of water.

(Photo by Glenn P. Knoblock)

Muskrats live year-round in bank dens or lodges made of vegetation and mud. In the winter, groups of muskrats will share the same lodge, possibly to provide warmth to each other. When vegetation becomes scarce in winter, they will eat small water animals such as crayfish, mussels, clams and snails. 

So while some mammals hibernate for the winter, many are still active during the coldest months, gathering food or hunting prey. And those that do take long winter naps, spend a lot of time and energy gathering food in preparation for the scarcity of the season. 

As you sit inside this winter, sipping a hot beverage and yearning for spring, give a thought to your fellow mammals and their amazing wintertime survival skills. 

Back to Top