Every September arctic ground squirrels in Alaska, Canada and Siberia retreat into burrows more than a meter beneath the tundra, curl up in nests built from grass, lichen and caribou hair, and begin to hibernate...

Every September arctic ground squirrels in Alaska, Canada and Siberia retreat into burrows more than a meter beneath the tundra, curl up in nests built from grass, lichen and caribou hair, and begin to hibernate...
 Seven months later the squirrels wake up and return to the surface—famished, eager to mate and perfectly healthy.
#squirrelsaturday  
http://www.scientificamerican.com/article.cfm?id=arctic-ground-squirrel-brain