Woodchucks are considered diurnal in their aboveground activities, although they have been observed feeding in dim light or even at night, especially when food is scarce. In the spring and autumn, activity peaks near midday and late in the day. In the summer, the animal appears more active in the morning and afternoon, preferring clear and sunny skies for maximum activity. When not feeding, woodchucks sun, scratch, and preen themselves outside their den while watching for potential enemies. When alarmed, a woodchuck gives a loud, shrill whistle.
Teeth grinding and chattering are common when woodchucks are cornered.
Woodchucks have also been heard to bark, squeal, and whistle when fighting with other woodchucks. Dens are situated in well-drained locations. With strong, clawed, forelimbs and large teeth, woodchucks can easily construct burrows with as many as five entrances. A plunge hole is often near the major den entrance and may have a vertical drop of as much as 2 ft to a main tunnel. These dens are also very long, up to 45 ft of tunnels, extending as far underground as 5 ft.