Son of the forest

Red Squirrel, Sciurus vulgaris

Here in Finland squirrels changing their colors for winter time to grey

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Tree squirrels do not hibernate during the winter months, but they keep all activities to a minimum to conserve energy. Hence, they often seem almost completely to disappear during the winter months. Winter tree nests (called dreys) are often shared for warmth where tree squirrels keep warm by snuggling with their family members. When they sleep, they use their big furry tails to cover themselves to keep as warm as possible.

A squirrel will come out now and then to search for hidden stores of food. These stores of nuts and other items (like pine cones in the case of the red squirrel) are buried by a squirrel in the ground in late autumn, a period also spent on instinctive binge eating.

citation : http://wiki.answers.com/Q/What_do_squirrels_do_during_winter