Life Under Snow
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With deep snow , many small mammals abandon the visible landscape. But if we could see beneath the snow cover, we would find a very active world.

Hi, I'm Bryan Yeaton and this is the Weather Notebook.

Mice and other small mammals build complex tunnel highways beneath the snow to link their burrows with food storage sites. These tunnel s limit exposure to the worst cold and many predators, and provide a means for fresh air to enter burrows.

Why is snow so important to the winter survival of many animals?

The air spaces between the snow crystals in a blanket of loosely packed snow serve as insulation -- a deep-freeze duvet -- for the ground below. So, while a deep snow layer may have its upper surface drop to extremely cold temperatures, the ground temperature beneath may remain around freezing. An extra few degrees of warmth over the winter can mean life or death to many animals, even hibernators.

Snow banks also provide excellent shelters for larger animals. Birds such as the ruffed grouse burrow into snow banks for warmth during extreme winter conditions. Even birds that are not associated with ground-living such as sparrows have been observed burrowing into snow banks for shelter, adding the snow's insulation to that of their feathers.

Soil too acts as a thermal insulation for creatures living underground. Where soil is deep and light, its surface may freeze solid, but three to six feet down, its temperature may not vary much over the year --perhaps a degree or two compared to 120 Fahrenheit degrees or more at the surface. Thus, many burrowing animals live much of their lives in a fairly constant thermal environment.

Thanks today to writer and meteorologist, Keith Heidorn of Victoria, British Columbia. The Weather Notebook is a production of the Mt. Washington Observatory and supported, in part, by Subaru of America.