This is the tunnel of the eastern mole (Scalopus aquaticus) that we have all seen in our yards.

Southern shorttail shrew (Blarina carolinensis) tracks heading in the direction of the arrows.  They are the darker spots indicated by the arrows.  The tracks are often indistinct, but if one sees a bounding pattern or walking pattern in snow, very soft mud, or dry sand that is too small to be anything else (except an insect, and insects have very different track patterns) it is probably a shrew.  Shrews are also noted for diving under snow, tunnelling, and then resurfacing again.  Trail Width: 29 mm (1 1/8 in)