Wildlife Readying for Winter
Frills become forms in hoarfrost as approaching winter pares back the abundance of summer. Each wild plant and animal is challenged by the impending cold and diminished food. When hardwood leaves start drifting to gild the forest floor, fir trees begin to shed about a third of their older needles. Waxes and resins are exuded to seal the remaining needles and buds against the drying effects of wind and cold. Animals find many ways to ready themselves for the plunging temperatures. So do I.
My attention gravitates toward the woodpile, where signs of winter wildlife preparation are everywhere. Chipmunks scurry by, pouches filled with more booty for the pantry, or new bedding material for underground sleeping chambers.
No longer friendly and inquisitive, they are munks on a mission. Red efts (a kind of salamander) have burrowed into the bark-rich ground made damp and fertile by my years of wood cutting and splitting. Uncovered, I gently move them to a safer, similar site.
Digging up soil one mid-September day, I found a dead-looking meadow jumping mouse about 25 cm (10 inches) underground. This species is called kangaroo mouse for its long hind legs and spectacular bounds. How high? I once lived in a drafty farmhouse where tucking in the sheets at night was necessary to keep them from blowing away-with the windows closed. One summer morning, after hearing a strange sound in the night, I found a drowned jumping mouse in the toilet! One more reason to keep the lid down.
The mid-September meadow jumper was already hibernating, even though the ground was still warm. Many other mice, shrew and vole species stay active over winter. Sausage-shaped meadow voles and doe-eyed deer mice launch a full-scale assault each fall on our barn and garage, which apparently garner a five-star rating for winter accommodation. From there they can foray under the snow to the smorgasbord that descends from each bird feeder.
While mice move in, moose leave the open bogs, marshes and lakes where combinations of wind and water offered some relief from the summer's insects and heat. Many moose migrate to traditional wintering sites in nearby forests. With larger bodies and less surface area exposed per unit of weight, moose are adapted to extreme cold weather and deep snows better than white-tailed deer. White-tails shed a reddish summer coat for a thicker, brown one with hollow hairs to provide insulation. During very cold weather their body metabolism slows down to conserve energy. Freezing rains are more problematic, wetting fur and resulting in serious heat loss. Deer tend to lose weight, no matter how much they eat, when temperatures dip below 5ºC. The smart ones move off exposed high ground to sheltered valley bottoms. Ideal wintering sites offer feeding areas located near dense softwood forests that serve to block out the wind chill. Along ice-free parts of Atlantic Canadian coasts, herds of white-tails overwinter in spruce/fir thickets along the shore and survive by eating seaweed. It's not in the texts, but they don't read them.
Insects burrow into the ground, or hide in tree crevices and rotting wood for the winter. Many species have a dormant larval stage, sometimes called a pupa, adapted to endure winter's elements. Some aquatic insects spend the winter as eggs, waiting for warm water in the spring to trigger a hatch. Adult blow flies and wasps are crawling under the cedar shingles of the house siding in hopes of emerging intact next spring. Fortunately they do little harm and go their way when warm weather arrives.
Cold-blooded creatures like northern leopard frogs, meanwhile, move to wet areas like marshes, ponds and streams as the water temperature drops. Along with species like green frogs and painted turtles, they burrow into weeds and mud bottoms. To be successful, they must avoid freezing, yet stay cold enough to slow their metabolism for as long as six months. These animals do not breathe while hibernating, but some oxygen is absorbed through skin and throat linings. Lactic acid from even low metabolism gradually permeates their bodies. Turtles use minerals in their shells to moderate body acid levels, while northern spring peepers and wood frogs actually tolerate freezing. While in this "frogsicle" state, hearts stop beating, and glucose sugars or glycerol in their bodies act like antifreeze. When they wake up in the spring, peepers and wood frogs burn off high blood sugar levels that would be toxic to humans by hopping down to the pond, forming a choir, and opening the breeding season.
Abandoned woodchuck, red fox, coyote and chipmunk burrows are critical wintering habitats for many small land animals seeking shelter, in much the same way as woodpecker holes become critical refuges for other birds and tree climbers. A range of animals like Maritime garter snakes, northern ringneck and eastern smooth green snakes, toads, yellow and blue-spotted salamanders and snowshoe hares (rabbits) occupy these dens below the frost line. The northern redbelly snake, one of my favourites for its slug-eating in the garden, regularly overwinters in ant mounds.
While many mammals shed thin summer fur for thicker winter insulation, short-tailed weasels and rabbits (snowshoe hare), undergo colour changes from brown to white with the moult. This camouflages the bearer in snow for two very different reasons. Weasels use the disguise as ermine to stalk and kill their prey; rabbits try to blend in to their surroundings and avoid predators.
Some mammals, like the woodchuck, meadow jumping mouse and little brown bat truly hibernate. Heart and breathing rates drop while body temperatures lower significantly, as general body activity-as well as energy demand-slows down. During this time, stores of fat serve as insulation and a source of nutrition.
A woodchuck's body temperature can lower to 3ºC, its heartbeat from a normal 80 per minute to five. They're comatose.
On the other hand, if you find yourself breaking through a snowdrift over a windfall and stumbling into a black bear den, be prepared to exit quickly.
Bears slow down, but not as much as meadow mice or woodchucks. Females give birth in January and February and nurse cubs over the winter. A warm spell will occasionally flood bears out of den sites, leaving them wandering about as unhappy campers for a time.
Chipmunks, flying squirrels, raccoons and skunks become torpid in winter, but do not actually hibernate. Many awaken regularly, go about the matters of breeding, eating and excreting, then return to sleep. Chipmunks awaken more often when they have lots of food in their stores.
Above the slumbering chippie chambers, snow swirls into ever deepening drifts. Red squirrels tunnel under the snow at mid-day to caches of dried mushrooms and softwood cones. At our place, they also guard ample stores of walnuts, much to my chagrin. Under the river ice not far away, adult trout and Atlantic salmon seek out quiet backwaters or pools. They do slow down, but remain active and feed only occasionally, since digestion in cold water takes much longer. In trees near the river, a snowy owl perches overlooking a field. Driven by hunger, these owls, along with others like snow buntings and northern shrikes, migrate to Atlantic Canada from the north to conserve their energy and find sustenance.
They're all getting by as best they can until a new spring arrives.