When temperatures drop significantly, mammals that stay active in the winter have a variety of ways to keep warm, one of which is to have layers of insulation to prevent their body heat from escaping. Often there is a layer of fat under the skin. In addition to providing a source of energy, fat doesn’t transfer heat as well as other tissues such as muscle or skin, and thus helps to insulate an animal’s body. The next layer consists of a short, dense coat of underfur which is filled with air pockets that provide insulation. Lastly there frequently is a third layer of oily, water-repellent guard hairs which excel at keeping out water. They are often transparent and hollow, providing extra thermal insulation.
Voles, mice, shrews and red squirrels use elaborate tunnels systems under the snow to escape cold temperatures and strong winds. Flying Squirrels huddle together in groups to keep warm. Shivering is a warming technique used by many mammals, including humans. And some active animals, like the pictured Gray Squirrel, simply find a sheltered spot in the sun, close their eyes, and soak up the warmth! (Thanks to Jody Crosby for photo op.)
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