The groundhog (Marmota monax), also known as a woodchuck, 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 groundhog is a lowland creature. It is widely distributed in North America and common in the northeastern and central United States and Canada. Groundhogs are found as far north as Alaska, with their habitat extending southeast to Georgia.
The groundhog is the largest sciurid in its geographical range, typically measuring 40 to 65 cm (16 to 26 in) long (including a 15 cm (6 in) tail) and weighing 2 to 4 kg (4 to 9 lb). In areas with fewer natural predators and large amounts of alfalfa, groundhogs can grow to 80 cm (30 in) and 14 kg (31 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.
The etymology of the name woodchuck is unrelated to wood or chucking. It stems from an Algonquian (possibly Narragansett) name for the animal, wuchak. The similarity between the words has led to the clever tongue-twister:
- How much wood would a woodchuck chuck
- if a woodchuck could chuck wood?
- A woodchuck would chuck all the wood he could
- if a woodchuck could chuck wood!
Distribution and habitat
The groundhog prefers open country and the edges of woodland, and 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.
In the wild, groundhogs can live up to six years with two or three being average. In captivity, groundhogs reportedly live from 9 to 14 years. Common predators for groundhogs include wolves, cougars, coyotes, foxes, bobcats, bears, eagles, and dogs. Young groundhogs are often at risk for predation by snakes, which easily enter the burrow.
Despite their heavy-bodied appearance, groundhogs are accomplished swimmers and occasionally climb trees when escaping predators or when they want to 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, hence the name "whistle-pig". Groundhogs may squeal when fighting, seriously injured, or caught by a predator. Other sounds groundhogs may make are low barks and a sound produced by grinding their teeth. When groundhogs are frightened, the hairs of the tail stand straight up, giving the tail the appearance of a hair brush.
Mostly herbivorous, groundhogs primarily eat wild grasses and other vegetation, including 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 Sciuridae. Like squirrels, they also have been observed sitting up eating nuts such as shagbark hickory, and pecans, but unlike squirrels, do not bury them for future use.
Groundhogs are excellent burrowers, using burrows for sleeping, rearing young, and hibernating. The average groundhog has been estimated to move approximately 1 m3 (35 cu ft), or 2,500 kg (5,500 lb), of soil 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 14 metres (46 ft) of tunnels buried up to 1.5 metres (5 ft) underground, and can pose a serious threat to agricultural and residential development by damaging farm machinery and even undermining building foundations. William Schoonmaker dug out eleven groundhog dens finding the longest, not including side galleries, was twenty-four feet with the average of all being about fourteen feet. Typically there are two chambers, one nest for resting and sleeping, the other an excrement or toilet chamber. The nest may be about twenty to thirty six inches below ground and is about sixteen inches wide and fourteen inches high, located above the main burrow. Although dens differ somewhat, typically the den has a main entrance, spy hole, one excrement chamber in use, and one nest. Only one deviation was found where a mother and four young were living together. Measurements of this den, from the extreme entrances, were twenty-nine feet one way and twenty-four feet the other, an area more than twenty-five feet square.
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 three 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. Groundhogs are mostly diurnal, and are often active early in the morning or late afternoon.
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 31–32 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 two to six blind, hairless and helpless young. Young groundhogs are weaned and ready to seek their own dens at five to six weeks of age. Groundhog mothers introduce their young to the wild once their fur is grown in and they can see. They encourage their young to copy their behaviors and during this time may differ from usual routines.
Relationship with humans
Both their diet and habit of burrowing make them serious nuisance animals around farms and gardens. They will eat many commonly grown vegetables, and their burrows can destroy farm ponds and undermine foundations and there is a thriving business exterminating them. Jackson (1961) suggested that the amount of damage done by the woodchuck had been exaggerated and that excessive persecution by people had substantially reduced its numbers in Wisconsin. In intensive agricultural and dairying regions of Wisconsin, particularly in the southern areas, the woodchuck by 1950 had been almost extirpated. In some areas marmots are important game animals and are killed regularly for sport, food or fur. In Kentucky, an estimated 267,500 Marmota monax were taken annually from 1964 to 1971. (Barbour and Davis 1974)  Their preferred habitat of grassy areas near woods also makes them abundant along roads and highways where they often become the victims of passing cars.
Hibernation is of interest to scientists with speculation that something similar might be of advantage to humans in space travel, and periods of induced hibernation would benefits patients undergoing or recovering from types of medical treatment. (Bil Gilbert)
Very often the dens of groundhogs provide homes for other animals including skunks, red foxes, and cottontail rabbits. Red fox and skunk feed upon field mice, grasshoppers, beetles and other creatures that destroy farm crops. Indirectly, the woodchuck helps the farmer. In digging, the groundhog brings subsoil to the surface aiding in soil improvement. The woodchuck is a valuable game animal and is considered difficult sport when hunted in a fair manner.
A report in 1883 by the New Hampshire Legislative Woodchuck Committee illustrates the attitude of some people toward this animal. In part this report stated "The woodchuck, despite its deformities both of mind and body, possesses some of the amenities of a higher civilization. It cleans its face after the manner of squirrels, and licks its fur after the manner of a cat. Your committee is too wise, however, to be deceived by this purely superficial observance of better habits. Contemporaneous with the ark, the woodchuck has not made any material progress in social science, and it is now too late to reform the wayward sinner. The average age of the woodchuck is too long to please your committee...The woodchuck is not only a nuisance, but also a bore. It burrows beneath the soil, and then chuckles to see a mowing machine, man and all, slump into one of these holes and disappear... Your committee is confident that a small bounty will prove of incalculable good at all vents, even as an experiment , it is certainly worth trying; therefore your committee would respectfully recommend that the accompanying bill be passed."
Groundhogs may be raised in captivity, but 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 February 2 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 are Punxsutawney Phil, kept as part of Groundhog Day festivities in Punxsutawney, Pennsylvania.
Groundhogs are used in medical research on hepatitis B-induced liver cancer. A percentage of the woodchuck population is infected with the woodchuck hepatitis virus (WHV), similar to human hepatitis B virus. Humans do not get the hepatitis virus from woodchucks but the virus and its effects on the liver make the woodchuck the best available animal for the study of viral hepatitis in humans. The only other animal model for hepatitis B virus studies is the chimpanzee, an endangered species.
Groundhog burrows have been known to reveal at least one archaeological site, the Ufferman Site in the U.S. state of Ohio. Although archaeologists have never excavated the Ufferman Site, numerous artifacts have been found because of the activities of local groundhogs. They favor the loose soil of the esker upon which the site lies, and their many diggings for their burrows have brought to the surface significant numbers of human and animal bones, pottery, and bits of stone. Woodchuck remains were found in the Indian mounds at Aztalan, Jefferson County, Wisconsin (Somers, in Barrett, 1933:386) 
Robert Frost's poem "A Drumlin Woodchuck" uses the imagery of a groundhog dug in to a small ridge as a metaphor for his emotional reticence. A groundhog figures prominently in the movie Groundhog Day.
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