Marmota monax


Mus monax (Linnaeus, 1758), Maryland, United States. Eleven subspecies.


English: Groundhog, forest marmot, whistle pig; French: Marmotte commune; German: Waldmurmeltier; Spanish: Marmota canadiense.


16.5-26.2 in (41.8-66.5 cm), females 6.8-10.6 lb (3.1-4.8 kg); males 6.8-11.2 lb (3.1-5.1 kg). The underfur is gray with yel-

low tips, and the guard hairs are banded yellowish to reddish brown with white tips.


Central Alaska through Yukon and below Great Slave Lake, Northwest Territories to Labrador. The eastern range extends south to Georgia, Alabama, northwestern Louisiana, and Arkansas. The western range extends south through central British Columbia into northern Idaho.


Generally found in low elevation woodland-field ecotones, foraging in meadows, orchards, and pastures. Hibernacula preferentially constructed in soils with good drainage in hedgerows, woods, south-facing inclines, rocky areas, and even haystacks.


The Latin word monax means solitary and is appropriately assigned to the woodchuck because it is the only asocial marmot except during breeding and raising of pups. Dominant males aggressively defend hibernacula of females while subordinate males are transient. Approximately 65% of juvenile females and 90% of juvenile males disperse before their first hibernation, the rest remain within the natal home range and disperse the following year. Activity peaks in mid-day during spring and late summer. Although the woodchuck can facilitate heat loss through their feet and nose they will avoid the afternoon heat during mid-summer by seeking refuge in their burrows.


Alfalfa, clover, and dandelions are highly preferred but also forage on a wide variety of other plants and grasses. They have also been observed foraging for bark, twigs, and leaves in various shrubs and trees. Invertebrates and birds' eggs are also eaten.


Breeding occurs shortly after emergence from hibernation, which varies from February to March in southern areas of its range (New York and Pennsylvania) and March to April in more northern areas (Ontario). Pregnancy rates are lower for yearling females (10-25%) than for adult females (56-80%). Gestation is 31-32 days. Only a single litter of 3.4 to 4.6 pups are born per year per female. Litters up to nine pups have been observed. Young are weaned at 44 days.


Not threatened. Populations have proliferated in response to agriculture.


The woodchuck is celebrated annually in North America on Groundhog Day, February 2, for its spring prophecy. The folklore is that if the woodchuck sees its shadow on that day then the woodchuck will stay above ground because spring is close. If the woodchuck see its shadow, it will return to its den since there will be another six weeks of winter. Woodchucks are used as an animal model in studies of many human medical concerns in metabolism, endocrinology, reproduction, and neurology. They are used extensively in research on the hepatitis B virus (HBV) that can cause chronic liver damage in humans. A related virus known as woodchuck hepatitis virus causes a similar disease in woodchucks as HBV does in humans and therefore serves as a good animal model for studying infection and treatments of HBV in humans. Woodchucks are considered an agricultural pest. ♦

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