By Justin Smith, Oakwoods Metropark Interpreter
Winter is a season of transformation, and snow is one of its greatest agents of change. As the green and growing earth browns and draws into itself, both plants and animals shift from patterns of exuberant abundance to ones of brilliant survival. And snow, or the lack thereof, is one of the major factors in this shift.
Just an inch of the fluffy white stuff is enough to hide mice, voles and other small mammals from the hungry gaze of predators, and that same inch of snow also covers the many seeds on the forest floor that our winter songbirds seek. A good half-foot of snow might slow you or me down on a walk along our favorite Metropark path, but it isn’t enough to cause concern to a fox or coyote who carefully high-steps through the fluffy white stuff, delicately placing each hind foot in the hole left by the previous step. However, any more accumulation and these mid-sized mammals are forced to leap and bound, using up precious energy in this coldest time of the year.
Even deep snow benefits some of our animal neighbors. High drifts provide perfect cover for grouse to plunge into each evening, forming makeshift snow caves in which to survive the winter nights. Deep snow lifts up our native eastern cottontail rabbits so that they can nibble buds and branches far higher than they could normally reach. However, as the snow piles up, even our long-legged whitetail deer find travel both difficult and dangerously tiring.
But paradoxically, this deep snow traps life-saving warmth against the crust of the earth itself. Even in the dead of winter, the area where the snow meets the soil stays within a degree or so of freezing. This subnivian, or “beneath the snow,” space captures the heat radiating up from the earth, and as the bottom layer of snow continually melts and refreezes, a miniature crawl space develops just above the ground, with a snowy ceiling held up by thousands of tiny ice pillars. Even as wind chills hit -40 degrees in the air above, this well-insulated subnivian zone protects skittering mice, germinating seeds, and even the occasional creeping spider, still active in the wintertime beneath this blanket of snow.
So enjoy the beauty of winter in your favorite Metropark this season. And as you grab your snow shovel or maybe your favorite sled, think about all the other Michigan creatures whose lives are shaped by how they, too, deal with the fluffy white stuff we call snow.