Life and Habitat
Groundhogs or woodchucks are the major hole-digging mammal of eastern North America.
The average groundhog excavates over 700 pounds of dirt digging just one den, and a single groundhog may have four or or five dens scattered across its territory, moving in and out of them as crops and weather change.
Groundhog burrows are important shelter resources for red fox, gray fox, opossum, raccoon, and skunk, most of whom do not dig their own burrows, but simply occupy those of groundhogs.
Over the course of the last 300 years, as forests have fallen to farms, the population of woodchucks and mid-sized predators such as fox and raccoon, have skyrocketed.
All of these animals are classified as "edge" creatures that thrive on multiple food sources found where forests meet field and yard.
Today, there are more groundhogs, red fox, gray fox, opossum and raccoon in the United States than at any previous time in U.S. history.
The most common locations of permanent groundhog dens are fence lines and thickets bordering hay and corn fields, vegetable farms, and fruit orchards. Here tangles of multiflora rose, kudzu, honeysuckle and small trees provide the kind of cover that enable a groundhog to enter and leave its den, shielded from the rushing attack of farm dogs, coyotes, and fox.
Drainage is a critical issue for groundhogs. Dens are never dug in damp or swampy areas, and stony ground is avoided as well. Look for groundhog dens in hedge rows along the edges of rolling farms fields, often on slight rises or on gentle slopes.
The main entrance of an active groundhog den is fairly easy to spot, as a small mound of exposed dirt will be packed at the entrance, providing a small rise from which the groundhog can view the world, or sun itself.
Loose soil is a sign of an active den, as is the slightly musty smell of urine-soaked soil pushed out of the main entrance.
Grass growing in the den entrance is a good visual cue that a den is no longer in active use.
The side entrances, or bolt holes, of a groundhog den will be smaller than the main entrance. These bolt holes will also be better concealed, with dirt from at least one bolt hole pulled through the main den pipe, leaving almost no evidence of its existence if the vegetation is very thick.
The average groundhog sette will have three or four holes, though some very old settes may have as many as six or seven, and some newer settes may have only one eye.
The den pipe of a groundhog den may plunge straight down as much as two or three feet. It is very common for a groundhog pipe to have at least one or two right angles in it -- locations from which the groundhog can slash at foxes and dogs that might try to pursue them underground.
Den pipes may be anywhere from 15 to 50 feet long, and will typically contain one more underground chambers 2 to 6 feet underground. These den chambers are lined with dried grass for winter warmth, padding, and to form nests in which the young are whelped in early Spring.
The groundhog breeding season begins in mid-February, soon after the animals emerge from hibernation. Pregnancy lasts 31-33 days and the single, annual litter of 2 to 9 pups is born toward the end of March or early April.
At birth, baby groundhogs are naked, blind and helpless and measure less than four inches long. A baby groundhog opens its eyes when it is about 4 weeks old, but they seldom venture outside until they are between 6 or 7 weeks old. By midsummer, young groundhogs are about 20 inches long and weigh about four pounds. These "teenage" groundhogs will start to move out from their natal den, and dig their own "starter" burrows, often just a few dozen yards down the fence row.
Groundhogs are naturally solitary creatures except during breeding season, and by late summer, the rapidly growing first-year groundhog will have moved some distance away from its natal den in order to establish its own territory and dig its own "permanent" burrow.
Groundhogs are vegetarians, eating leaves, flowers and soft stems of various grasses, and field crops such as clover and alfalfa. Certain garden crops like peas, beans and carrots are favorites. Groundhogs occasionally climb trees to obtain apples and pears -- one reason they are disliked by many orchard owners.
Groundhogs are capable of consuming as much as three-fourths of a pound of vegetable matter a day -- the equivalent of a 175-pound person eating 15 pounds of salad a day. In order to maximize food intake, groundhogs will often dig summer burrows in the middle of pastures or meadows, so that that they do not have to go far to go to get to the "salad bar."
Groundhogs are considered a major agricultural pest in most areas, and most farmers are anxious to get rid of them or reduce their number. It is very common for a single groundhog to take a bite out of dozens of pumpkins in just a few days, ruining each of them for Halloween sale. The same kind of destruction is visited on bell peppers, squash and zucchini.
Another reason for the animosity between farmers and groundhogs can be traced to the fact that groundhogs are lazy animals. As a consequence, they tend to start new burrows anywhere a farmer has already disturbed the ground. This means that groundhogs see fence posts and new orchard trees as construction opportunities -- places where new burrows can be dug quickly and with a minimum of effort. The result: expensive new fences that are weakened, and orchard trees that may lose several years worth of growth as groundhogs trim away underground roots.
Groundhogs burrows can also be quite destructive to both livestock and to farm machinery. Groundhog dens may undermine a patch of ground to the point that tractors and cultivators fall into ditches and holes deep enough to break an axle or sheer an alignment pin. In addition, horses and cattle can step into den holes and break a leg -- a tragic occurrence that generally results in the death of the animal.
Groundhog skull, side and from top.
Teeth grinding and chattering are common when woodchucks are cornered. Woodchucks have also been heard to bark, squeal, and whistle when fighting with other woodchucks (see the quarry sounds page at http://www.terrierman.com/sounds.htm).
How big can a groundhog get? Adult groundhogs typically tip the scale at 8 to 10 pounds by fall, but larger groundhogs are fairly common. To see a few pictures of "big ones," go to: http://www.terrierman.com/bosshog.htm
Because groundhogs have short bodies, they tend to have relatively large chests for their weight. An adult groundhog will typically have a chest span of 12-15 inches -- about the same size as that of a red fox or a good working terrier. For more on this, see: http://www.terrierman.com/terriersizearticle.htm
Most groundhogs live only a year or less, but some groundhogs always survive disease and predation, and really large den holes that were once occupied by three- or four-year-old groundhogs are fairly common. To read more about groundhog mortality, see: http://www.terrierman.com/groundhogdeath.htm