I repeated my little gift of apple slices tonight and was surprised to find that the footprints that I had been seeing were actually the markings of a mouse.
Footprints in the snow
More by the door
The mouse comes out of the bottom of his little snow tunnel and walks to the top hole.
He then proceeds to shallowly tunnel under the snow every now and then.
He alluded me in getting a picture of him running around and making footprints in the snow, though.