Janesville20.3°

In brutal cold, life goes on under snow

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D.S. Pledger
January 26, 2014

I've written from time to time about what winter was like in the “old days” when I was growing up in Wausau.

The cold weather and snow blew in around Thanksgiving and then there were almost four months of unrelenting bitter cold with temperatures often sagging below zero for the high for the day.

Sound familiar? This year my childhood seems to be repeating itself weather-wise.

As I started this column, the 1:10 p.m. temperature in my hometown up north was 20-below zero in the heat of the day. The sun was shining brightly over a cover of deep snow, but with feeble January rays about as warm as a witch's heart.

This kind of extreme cold has many effects on nature's flora and fauna. On an icy winter night we used to listen to trees pop like the report of a .22 rifle as the moisture inside a limb froze and expanded, causing the branch to crack open.

Out on the lake, the groaning of “ice-making” could be heard, as pressure ridges formed due to expansion, and then buckled. On such a night one wonders how any living thing in the outdoors can survive such temperatures.

One group of woodland denizens that is shielded from much of winter's onslaught, however, is that which lives in a thin layer where the ground meets the bottom of the snow.

During the season's first snowfall, vegetation on undisturbed ground keeps the snow from packing down tight and creates small openings and cavities. When the snow is about 12 inches deep, the layer becomes a maze of tiny “snow caves” as the temperature stabilizes at a couple of degrees above freezing.

This is possible because of the fact that the earth is giving off a small amount of heat and the snow acts as an insulating blanket, trapping the warmth.

There is actually enough heat to form ice crystals and the small openings are enlarged. In this honeycomb, small creatures such as mice, voles and shrews make tunnels and can carry on their lives in comparative comfort, protected from the wind and bitter cold. Not only are they safe from the harsh environment above, but this “subnivean” layer, as it is correctly called, also offers sustenance.

Seeds keep well in it and some types of vegetation stay succulent all winter. Then too, the layer is used by insects, which add to the food source. Rodents are also known to chew bark from the bases of trees, but their foraging must be done in semi- or total darkness since the snow pack cuts off most of the sunlight reaching the forest floor.

Although it would seem that subnivean dwellers would be immune from predators, the keen ears of canids like the fox and coyote can hear the sound of them rummaging in their tunnels and will pounce on a noisy rodent.

I've watched Yellowtail, our Labrador, listen, then sniff and snuffle in the snow, then jump in headfirst like a fox—occasionally coming up with a mouse. Ermine have been known to enter a big tunnel complex and do their hunting beneath the snow, running down a mouse on its own turf.

There are some things that can destroy this ideal cold-weather environment, too. A mid-winter rain can saturate the ground, collapse the tunnels and force the inhabitants above ground where they're easy prey for owls and hawks.

During extremely cold and windless nights, enough heat is lost through radiation to cause the ground to freeze, which can also have adverse effects for those who live there.

In spite of the risks, living in a habitat sheltered from the wind where temperatures can be as much as 60 degrees warmer than those only a few feet above is a pretty good place to be during a winter—especially one that seems to have blown out of the 1950s.

D.S. Pledger is an outdoors columnist for The Gazette. Email him at maus16@centurytel.net.



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