Woodchucks breed in March and April. One litter of 2 to 6, usually 4 young is produced each year after a gestation period of about 32 days. Young are born blind and hairless, and weaned by late June or early July. They leave the nest soon after they are weaned. Young frequently occupy dens or burrows that are abandoned. New burrows that appear during late summer are generally dug by older woodchucks.
Burrows commonly are located in fields and pastures, along fence rows, stone walls, roadsides, building foundations, and bases of trees. The burrow serves as home to the woodchuck for mating, weaning young, hibernating, and protection. Woodchucks maintain sanitary den sites and burrow systems, and replace nest materials frequently. A burrow or den system is used for several seasons. The system is irregular and may be extensive. Burrows may be 5 feet deep and 8 to 66 feet long (Figure 4).
Burrows of woodchucks easily are identified by a large mound of excavated earth at the main entrance, called a porch. The main opening typically is 10 to 12 inches in diameter.
Many burrows have 2 or more entrances. The secondary entrances are dug from below the ground and do not have mounds of earth beside them, making them sometimes difficult to locate. The secondary entrances serve as escapes to, or away from, the den when pursued by predators. Burrows not in use by woodchucks provide habitat for rabbits, weasels, and other wildlife.
Woodchucks enter true hibernation, which generally starts near the end of October or early November and continues until late February and March. In northern latitudes, hibernation generally starts earlier and ends later. Males usually come out of hibernation before females and sub-adults, and may travel long distances in search of a mate.
The lifespan of a woodchuck is 3 to 6 years. Woodchucks usually range 50 to 150 feet from their dens during the daytime, which may vary during the mating season and depend on the availability of food. Woodchucks primarily are active during daylight. They sometimes bask in the sun during the warmest periods of the day and may doze on fence posts, stone walls, large rocks, or fallen logs close to the entrance of their burrow. Woodchucks can climb and sometimes are seen in lower tree branches.
In general, woodchucks prefer open farmland and wooded or brushy areas.
Woodchucks forage in the early morning and evening. They primarily are herbivores and feed on a variety of vegetables, grasses, and legumes. Preferred foods include beans, peas, carrot tops, alfalfa, clover, and grasses.