Animals Toughing It Out: Resisting the Stresses of Winter to be Active, Part 2

                                    Guest post by KVR Instructor, Cathy Chybowski

            Photo of Ruffed Grouse Courtesy of EEK! Wisconsin: Environmental Education for Kids eekwi.org                                 

Like animals that migrate or hibernate, animals that are active in the winter have evolved key adaptations that help them avoid or confront harsh conditions. An adaptation can simply be making use of fur, fat, or feathers. Mammals grow heavy undercoats and long hollow guard hairs to trap air for better insulation. Birds can fluff out their feathers or tuck their heads under their wings for warmth. A grouse spends the day foraging and filling its crop with food. Then it dives or burrows into deep snow, slowly digesting its food, warm beneath a blanket of snow.  

Animals living farther north tend to have larger bodies and smaller appendages. A large body loses heat more slowly than a small body. Shorter appendages radiate less heat than longer ones. Many animals living in the north turn white in winter. The obvious advantage is camouflage for both predator or prey. But another advantage is that white feathers and fur contain more air than pigment so provide better insulation than fur or feathers with color. In summary, it is better to be big and white in winter. Think polar bear! It has a large body, short ears, tail and legs, and white fur. It is perfectly adapted for living in a cold, snowy landscape.

Snow is a mixed blessing. For small mammals like voles, it can provide both insulation and protection from predators. For animals like deer, it can make travel difficult.

The meadow vole, sometimes called a field mouse, spends most of the winter under the snow in a system of tunnels leading to a communal nest. It is an exception to the “better to be big and white” rule.

Photo of Meadow Vole courtesy of EEK! Wisconsin: Environmental Education for Kids eekwi.org 

To compensate for its small size and brown color, it actually loses weight before winter in order to reduce its need for food. Because it is an important part of the food web, it seldom ventures above the snow. Still, foxes and coyotes hear voles moving under the snow, jump up and down to collapse their burrows, trapping them and then retrieving them. Two to three months before the snow has melted, still snug and protected, voles begin to reproduce. A young female can mate at one month of age and produce as many as 17 litters per year with 5 or more young per litter. Look for the tracks of these small mammals on top of the snow or the quarter-sized entrance holes to their tunnels beneath the snow. As the snow melts, the topless tunnels reveal well-traveled runways beneath.

The white-tailed deer is an energy conservation specialist. Whenever possible, it does not expend more energy than it takes in. It grows a thick, woolly underfur and an outer fur with long hollow guard hairs for insulation and it relies on fat reserves built up in the warm months to fuel its activities in the winter. When the snow is deep, deer yard up and follow well worn paths to evade predators and conserve energy. Their digestive system changes to accommodate a change in diet—grazing in the warm months to browsing in the winter months due to the snow cover. When you are outside, look for deer browse, tracks, scat, beds, buck rubs, or antlers usually shed in late winter.

Photo of White-Tailed Deer Courtesy of EEK! Wisconsin: Environmental Education for Kids eekwi.org 

As a group, birds face three obstacles to winter survival: cold temperatures, starvation, and predation. Birds have a higher metabolic rate and a higher body temperature than mammals, therefore making surviving the cold more difficult.The food supply is diminished and often unreliable. Snow can limit access to otherwise available food.  Predators are ever present.  Small birds like chickadees, nuthatches, kinglets, brown creepers and titmice join mixed flocks. More eyes reduce the possibility of a predator attack and broadens the search for food. Sometimes these flocks even roost together in a tree cavity, bluebird nest box, or other shelter. Some birds like blue jays, chickadees and nuthatches store food for later consumption and many birds frequent our feeders when the weather turns harsh or there is deep snow cover.

The black-capped chickadee is another exception to the “better to be big and white” rule. In order to maintain its body temperature in winter, it requires 20 times more food than in the summer.  How do they do it? Among the chickadee’s amazing physical feats is its ability to forage while hanging upside down and moving every which way, foraging for eggs and larvae of insects in bark crevices. Could this acrobatic method be an adaptation for winter feeding when snow covers the tops of branches, chickadees can still gather food from beneath?

Photo of Black-Capped Chickadee courtesy of EEK! Wisconsin: Environmental Education for Kids eekwi.org 

Unlike mammals, birds do not grow extra feathers for warmth in the winter.  Instead, they fluff their feathers to trap more air for added insulation, often tuck their heads under their wings, and huddle together under an evergreen bough with a snowy canopy.  

Aldo Leopold writes in A Sand County Almanac: “I suspect that in the chickadee Sunday School two mortal sins are taught: thou shalt not venture into windy places in winter, thou shalt not get wet before a blizzard.” Apparently a chickadee survives a frigid 16-hour night by doing lots of little things just right. As these tiny creatures wake with the sunrise, they begin foraging and this becomes the order of their day. By late afternoon they are “bulging with fat” which provides insulation. As the sun sets they lower their temperature as much as 15 degrees, settling into a nightly hypothermia, fluffing, tucking, and huddling till sunrise again, when the fat is depleted. Repeat. Repeat every 24 hours; it is a matter of survival. When you are out, listen for the chickadee’s voice and watch for their quick movements.

The next time you reach to turn the thermostat up, think about the challenges that animals face for winter survival and some of the amazing adaptations and strategies they have evolved to deal with them.

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We love the resources at EEK! Wisconsin, Environmental Education for Kids. They are hosting a live reading on December 2, 2020, at 10 AM CT, by author Laureanna Raymond-Duvernell from her book, Under the Mud, about 10 different animals and their winter survival adaptations. For more information or to register visit https://www.eventbrite.com/e/story-edventure-read-aloud-under-in-the-mud-tickets-127366770439 This event would be great for students in grades 3-8, and it is free. Educators are encouraged to register for their classes. Homeschooling and schooling-at-home families might enjoy this, too!