Sciuridae
Sciurus carolinensis
(eastern gray squirrel)

Image Caption:
An eastern gray squirrel sits on an oak branch in winter.  Eastern gray squirrels are non-hibernating homeotherms (warm-blooded animals) that maintain a body temperature of 37 to 40 degrees Celsius.  When outside their nest, the tail and fur act to decrease heat loss, but even so, in cold weather, squirrels must shiver to stay alive.  About three quarters of the heat lost to cold air is regained by shivering, and if need be, squirrels can generate 10.3 times more heat than their standard metabolic rate by shivering, the highest reported rate for any mammal. (Feldhamer et. al, 2003).

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Eastern Gray Squirrel (Sciurus carolinensis carolinensis) on Tree Branch
Works Cited:

Feldhamer, G. A., Thompson, B. C., & Chapman, J. A.  (2003). Wild Mammals of North America.  JHU Press.
Image Location: United States, Virginia, Norfolk
Image Date: 2008JAN13
Image Species:  Sciurus carolinensis carolinensis
(EXIF information is accurate – stamped in UTC).

Web Page and Pictures By Peter Leitheiser
Updated: 2009JAN01