Squirrels Bulk Up During Hibernation

Squirrels build up muscle mass despite inactivity, during the last weeks of hibernation.
Thirteen lined ground squirrel (courtesy Phil Myers)
The thirteen-lined ground squirrel, named for its many stripes, lives on the prairies and grasslands of North America. Like many hibernators, it survives the winter months by living off body fat, slowing its heart rate and metabolism and lowering its body temperature. But researchers were mystified by how the squirrel is able to emerge from months of hibernation in such good physical shape, without any exercise or nutrition. Dr. Alysson Hindle, a Canadian scientist studied this mystery in laboratory conditions at the University of Colorado. MRI's conducted periodically throughout hibernation revealed that two months prior to emerging from their dormancy, the squirrels start building up muscle mass - even though their overall body weight is down by as much as 40 percent. In the future, it is hoped that understanding where the muscle building resources come from in the squirrel can be applied to humans who suffer from muscle atrophy.  

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