Guest post by KVR Instructor, Cathy Chybowski
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| 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.
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| 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.
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| 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?
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| 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!
