They are restricted in their ability to add insulating fat and/or fur and depend on sufficient snowpack for winter survival. To maintain a relative heat balance in the face of decreased air temperatures, they minimize body-air temperature differences by remaining under the subnivian layer. The subnivian layer is the area above the soil and below the top of a snowpack that can be several millimeters to several centimeters deep.
Snow reflects the sun's warming radiation and is a thermal blanket under which much biological activity takes place through the winter season. Snow can be a nuisance to those animals that must scratch through its sustenance for food but it is the salvation and protection to many animals and several plant species that depend on it through the cold. Snow separates two distinct worlds; the ours and the world beneath the snow. Therefore, the next time you are walking, hiking, skiing and snowshoeing this season, think about the world under your feet and tread lightly.