How Woodchucks Spend Their Time?

Two woodchucks live under the spring house. I don't know whether they are even acquainted with each other. They are so skittish that even the act of looking out the window at them sends them rumpling back into their holes. They are the same color as the stones on their front door step.

Yesterday would have been a perfect day for basking, but I never caught them at it. The day before, though, the one who lives in the lower flat came out as far as the apple tree, selected an apple, and then went home via a circuitous route over the rock pile down wind, as if to be sure he wasn't followed.

What on earth can they be doing down under ground all this time? Intensifying their baseless suspicions of each other?