National Geographic : 1925 May
594 THE NATIONAL GEOGRAPHIC MAGAZINE EXCAVATIONS MADE IN SEARCHING FOR HIBERNATING SQUIRRELS At first, for fear that they were missing the squirrels, the investigators carefully followed every burrow. Later, before beginning the work of careful excavation, deep trenches were dug down to subsoil completely around the main body of the den for fear the squirrels might awaken and escape through some radiating burrow. A fairly large den may cover a radiating area of 30 by 40 feet. From the knife at THE VERTICAL SECTION OF A HIBERNATING DEN the left is. first, the exposed nest; next, the round hole leading upward for the spring exit; and then the drain leading downward.