By Boak Wiesner
Snow lightly fell as I made my slow way west on the snowshoe trail. Its packed surface let me walk without my ‘shoes on, actually. This winter of fluffy snow and cold has allowed no crusts form and this makes snowshoeing very arduous when one goes off trail. At the same time, those conditions make the sub-nivean world, under the snow, a much warmer prospect. More on that later.
Reducing foot-load is the purpose for using snowshoes. Each type of snowshoe has its specific uses. I prefer the design attributed to the natives of this area, since that’s where I live. I figure, logically, that a couple of hundred generations of trial-and-error has produced the most efficient design.
The narrow toe lets one jam it through brush and cattails which are then pushed aside like a snowplow. The narrow toe design also let one walk much more normally without so much porcupine-like waddling, as the empty area of one shoe lets the wide area of the other fit. Remember to dorsiflect as you ‘shoe! That means: lift up your toes instead of pushing them down as one would on a sidewalk. You know you’ve done it right when your anterior tibialis muscles are stiff the next day. Toeing-up lets the tail of the ‘shoe act like the skeg of a skiff as it trails behind you which helps them track straight.
Considering the foot-load characteristics of mammals around Minnesota, the winners are, as you might have guessed: lynx, snowshoe hare, and caribou.
Why are there so many romantic songs about rain but so few about snow, when it is this very white stuff that defines the North Country? How does snow help animals survive? How effective is the snowpack as an insulator anyway?
To test this, Monday morning, I made a quick snow-top measurement – yep: darn cold!
Then I dug a snow pit, so I could get measure the thickness of the snowpack and the temperature at the bottom: a balmy -3⁰C! (+27 F.) The difference in temperature between bottom and top is called the temperature gradient. 40 degrees Fahrenheit across just 13 inches of snow – now that’s a good insulator!
Why so warm at the bottom? The heat that the ground absorbed last summer and fall is still there. Some did radiate out as the fall progressed. Until the snow fell. Now there’s a nice, fluffy blanket on the ground which doesn’t let much of that warmth escape. The warmth deeper down in the ground has spread out until it has reached the surface of the soil. 27 degrees is really not all that cold, so small mammals have a relatively easy time of it down there. Plus they are out-of-sight from predators like hawks and owls. Weasels can still get them, though.
Boak Wiesner is a Minnesota Naturalist volunteer.