The groundhog (Marmota monax), also known as the woodchuck, land beaver or whistlepig, is a rodent of the family Sciuridae, belonging to the group of large ground squirrels known as marmots. Other marmots, such as the yellow-bellied and hoary marmots, live in rocky and mountainous areas, but the woodchuck is a lowland creature. It is widely distributed in North America and common in the northeastern and central United States. Groundhogs are found as far north as Alaska, with their habitat extending southeast to Alabama.
The groundhog is the largest sciurid in its geographical range, typically measuring 40 to 65 cm (17 to 26 in) long (including a 15 cm tail) and weighing 2 to 4 kg (4.5 to 9 pounds). In areas with fewer natural predators and large quantities of alfalfa, groundhogs can grow to 80 cm (32 in) and 14 kg (30 lb). Groundhogs are well adapted for digging, with short but powerful limbs and curved, thick claws. Unlike other sciurids, the groundhog's spine is curved, more like that of a mole, and the tail is comparably shorter as well – only about one-fourth of body length. Suited to their temperate habitat, groundhogs are covered with two coats of fur: a dense grey undercoat and a longer coat of banded guard hairs that gives the groundhog its distinctive "frosted" appearance.
Groundhogs usually live from two to three years, but can live up to six years in the wild. In captivity, groundhogs can exceed this limit; by example, the 22-year-old Wiarton Willie may indicate the maximum lifespan. Common predators for groundhogs include wolves, coyotes, foxes, bobcats, bears, large hawks, and owls. Young groundhogs are often at risk for predation by snakes, which easily enter the burrow.
Mostly herbivorous, groundhogs primarily eat wild grasses and other vegetation, and berries and agricultural crops when available. Groundhogs also eat grubs, grasshoppers, insects, snails and other small animals, but are not as omnivorous as many other sciurids.
Groundhogs are excellent burrowers, using burrows for sleeping, rearing young, and hibernating. The average groundhog has been estimated to move approximately 1 m³ (35 cubic feet), or 320 kg (700 pounds), of dirt when digging a burrow. Though groundhogs are the most solitary of the marmots, several individuals may occupy the same burrow. Groundhog burrows usually have two to five entrances, providing groundhogs their primary means of escape from predators. Burrows are particularly large, with up to of tunnels buried up to underground, and can pose a serious threat to agricultural and residential development by damaging farm machinery and even undermining building foundations.
Groundhogs are one of the few species that enter into true hibernation, and often build a separate "winter burrow" for this purpose. This burrow is usually in a wooded or brushy area and is dug below the frost line and remains at a stable temperature well above freezing during the winter months. In most areas, groundhogs hibernate from October to March or April, but in more temperate areas, they may hibernate as little as 3 months. To survive the winter, they are at their maximum weight shortly before entering hibernation. They emerge from hibernation with some remaining body fat to live on until the warmer spring weather produces abundant plant materials for food.
Despite their heavy-bodied appearance, groundhogs are accomplished swimmers and climbers, and climb trees to escape predators or survey their surroundings. They prefer to retreat to their burrows when threatened; if the burrow is invaded, the groundhog tenaciously defends itself with its two large incisors and front claws. Groundhogs are generally agonistic and territorial among their own species, and may skirmish to establish dominance.
Outside their burrow, individuals are alert when not actively feeding. It is common to see one or more nearly-motionless individuals standing erect on their hind feet watching for danger. When alarmed, they use a high-pitched whistle to warn the rest of the colony.
Usually groundhogs breed in their second year, but a small proportion may breed in their first. The breeding season extends from early March to mid- or late April, after hibernation. A mated pair remains in the same den throughout the 28-32 day gestation period. As birth of the young approaches in April or May, the male leaves the den. One litter is produced annually, usually containing 2-6 blind, hairless and helpless young. Young groundhogs are weaned and ready to seek their own dens at five to six weeks of age.
The groundhog prefers open country and the edges of woodland, and it is rarely far from a burrow entrance. Since the clearing of forests provided it with much more suitable habitat, the groundhog population is probably higher now than it was before the arrival of European settlers in North America. Groundhogs are often hunted for sport, which tends to control their numbers. However, their ability to reproduce quickly has tended to mitigate the depopulating effects of sport hunting. As a consequence, the groundhog is a familiar animal to many people in the United States and Canada.
Groundhogs raised in captivity can be socialized relatively easily; however, their aggressive nature can pose problems. Doug Schwartz, a zookeeper and groundhog trainer at the Staten Island Zoo, has been quoted as saying "They’re known for their aggression, so you’re starting from a hard place. [Their] natural impulse is to kill ’em all and let God sort ’em out. You have to work to produce the sweet and cuddly."
In the United States and Canada, the yearly Groundhog Day celebration has given the groundhog recognition and popularity, as has the movie of the same name. The most popularly-known of these groundhogs is Punxsutawney Phil, a groundhog kept as part of Groundhog Day festivities in Punxsutawney, Pennsylvania.
The etymology of the name woodchuck is unrelated to wood or chucking. It stems from an Algonquian name for the animal (possibly Narragansett), wuchak. The apparent relationship between the two words has led to the common tongue twister: "How much wood would a woodchuck chuck if a woodchuck could chuck wood? — A woodchuck would chuck as much wood as he could if a woodchuck could chuck wood". Various response lines can answer this, including:
Groundhogs are sometimes eaten for food.