In the winter squirrels don't hibernate; they will often be well stocked on food and stay up in their nests to keep warm. I know when I see snow cover and low temperatures, it might be days before I see one or even a sign of one. Eventually, though, they will venture down from their tree and have to find some more food, or they will go find a stash they made when it was warmer. This one looks like he found some nuts on the ground and must have been hungry because he sat there munching away, not a care in the world other than the nut he just found.
