woodchuck or groundhog, common name of a North American species of marmot, Marmota monax. This large rodent is found in open woods and ravines throughout most of Canada and the NE United States. Its heavyset body is about 2 ft (60 cm) long, excluding the 6 in. (15 cm) tail, and is covered with thick, coarse, brownish hair. A terrestrial, day-active animal, it feeds on green vegetation. It has benefited by the clearing of forests for cultivation, and, despite the attacks of farmers, its numbers have increased. It nests in a burrow of many compartments, where it also hibernates in winter. According to an old superstition the groundhog leaves its burrow on Feb. 2, Groundhog Day, and returns underground for six weeks if it sees its shadow; thus, a sunny Feb. 2 supposedly means six more weeks of winter. Woodchucks are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Rodentia, family Sciuridae.