Rick Baetsen
Chickadee in winter
Chickadees and other birds and animals face winter head on, adapting to the cold clime. The other two ways that animals cope with winter is to flee (migrate) or to go into hiding (dormancy).
Winter is a long season to endure, though we’ve altered our behaviors and thought up survival schemes. Take those triple-lined Sorels, the robust engine-block heater, the hot toddy and the midwinter escape to Cancun. These are adaptations. Survival, while remaining sane, is our goal.
Animals face the same arduous winter and have adapted, handling the hard fact of winter by: Heading for warmer locations (migration), going into hiding (dormancy) or facing the music (cold out there).
Move on – Dozens of species cope by migrating. Some birds, such as the golden-winged warbler, fly thousands of miles to Central and South America to bask away winter. Common loons travel to the Gulf of Mexico and the southeastern United States. Bald eagles fly as far south as it takes to find open water. White-tailed deer also migrate, and although their destination is not a tropical paradise, it does offer refuge. Deer may migrate dozens of miles to wintering sites called deeryards. These conifer habitats offer thermal protection from biting cold and shelter from deep snow. Deer develop intricate, lattice-work trail systems for easy travel to save energy for eluding predators or just surviving.
Stay put – Although there are discrepancies about what makes a “true hibernator,” one thing is certain: Many northern species undergo metabolic changes to “sleep” through winter. Some animals, unable to leave but not built for the harsh conditions, go into hiding. Amphibians hide in muck and mud under lakes and ponds or remain submerged under the ice and take in oxygen through their skin. They become more corpse-like than living. Their heart rates decrease, body temperatures drop and some cease to breathe. Species such as spring peepers, chorus and wood frogs produce a glycol-like antifreeze that retards formation of ice crystals and prevents their cells from freezing. In every other regard, when temperatures hit frigid, these creatures freeze solid, only to thaw come spring. Insects winter in a dormant state as eggs, pupae or adults and are often armed with specialized chemical adaptations.
Larger creatures also go into hiding. Some researchers refer to black bears as highly efficient hibernators while others believe bears don’t hibernate at all. A bear’s metabolic rate is reduced by half in winter, but it maintains a temperature greater than 88 degrees (12 degrees lower than summer). Unlike other hibernators, bears will wake up and be active for brief periods. During the long cold months, black bears live solely off their accumulated body fat. That’s why they eat every waking minute in spring, summer and fall, gorging on carbohydrate-rich berries and other foods. They gain up to 30 pounds per week. A black bear’s winter cholesterol level is two times higher than in summer, more than twice a human’s normal level. Black bears do not urinate or defecate in winter. Instead, their body chemically breaks down these toxins and reuses them as energy. Researchers are studying the bear’s uncanny hibernating abilities to apply what they learn to organ preservation, kidney disorders, human hibernation and long-distance space travel.
Meet it head-on – Winter coats in fur or feather play a key role in survival. Some mammals have a dual winter coat. Longer outer, or guard, hairs act like a raincoat, deflecting moisture. Under, or insulating, fur provides an extra layer. A few northern species change fur color. Snowshoe hare and weasels (long-tailed, short-tailed and least weasels) change to white, camouflaged in snow. Others in the weasel family, such as mink and otter, build thick layers of insulating fat and special fur to keep dry.
Certain animals use their fur and feathers in ingenious ways. Wolves, coyotes and foxes keep their feet warm by growing stiff bristly hairs around their toes for insulation and traction. These canines have special blood vessels in their footpads to keep their feet just above the freezing point, preventing buildup of snow and ice. While snoozing, canines wrap their bushy tails around their feet and nose – retaining the warmth they exhale and recycling it into their feet. Ruffed grouse develop a protective feather coating on their feet and grow feathers to protect their nostrils from snow.
Canada lynx, a true northern cat, uses its long legs to maneuver in dry, fluffy snow and gigantic snowshoe-like feet for support on the snow while hunting its main prey, snowshoe hare.
Certain weasels and birds change activities to rest more and forage less. Pine marten spend time in subnivian (under the snow) hunting tunnels developed by tiny mammals. Time under snow protects animals from the elements and predators. Ruffed grouse “snow roost” under the snow to elude raptors and stretches of extreme cold.
And what about our tall north woods giants? Trees transfer sugars and import food reserves to their root systems. Deciduous trees lose leaves in the fall while conifers develop a waxy coating called cutin over their needlelike leaves. Conifers create growth patterns to minimize damage from snow and ice accumulation.
Yes, we creatures of the north have little choice but to adapt to make it to spring. When spring arrives – the running of melt water, the peeper’s sleigh bell call, the bright yellow marsh marigolds, the smell of thawing earth – it’s a time made sweet by a winter wait.
Pam Troxell coordinated the Timber Wolf Alliance at the Sigurd Olson Environmental Institute on the campus of Northland College in Ashland, Wisconsin. She passed away in October 2007.