(Marmota monax Erxleben)
From: Saunders, D. A. 1988. Adirondack Mammals. State University of New York, College of Environmental Science and Forestry. 216pp.
The woodchuck or groundhog is the largest member of the squirrel family in the Adirondacks and has grizzled, coarse fur. Above, the fur is brown to blackish brown, tipped with buffy yellow, white or cinnamon brown, except for the top of the head and most of the tail. The underparts are yellowish orange to chestnut. The cheeks and chin are buffy white to pale brown. Black (melanistic), partially black, or more commonly, blackish brown color phases, the guard hairs glossy (and lacking light) colored tips, are common. The body is compact, the legs short and thick, the head broad, short, and flat. The bushy tail is short, about 10- 15 cm (4-6 in) in length. The short, rounded ears and eyes are located at the top of the head, enabling a woodchuck to survey the area around the burrow without exposing most of the head. Large woodchucks are approximately 60 cm (24 in) in length, and weigh 13-33 kg (6-12 lb), the heavier weight typical of individuals entering hibernation.
Range and Habitat: The range is most of Canada, east-central Alaska, and much of the eastern half of the U.S. except for parts of the South and Southeast. The woodchuck is most abundant in the pastures, fields, and meadows of the Adirondack Park’s periphery, but it occurs throughout the entire region within the clearings, meadows, and edges of roadways and deciduous and mixed forests to elevations of at least 713 m (2340 ft). Roadsides and villages are places where the woodchuck is most common in the central Adirondacks.
Woodchucks live in burrows which they dig in dry, well-drained soils. Burrows may consist of simple tunnels about 15 cm (6 in) in diameter, or a series of interconnecting tunnels. The main entrance, marked by a fan-shaped mound of dirt and usually located at the edge of a large boulder or log, is about twice the diameter of a tunnels. One or more plunge holes, dug from within a tunnel and therefore lacking dirt mounds, serve as inconspicuous auxiliary entrances. Burrow systems, especially those used by succeeding generations of woodchucks, may extend 15-30 m (50-100 ft) in length, but rarely exceed 2 m (6 ft) in depth. The nest is a ball-shaped structure of plant fibers which a wood chuck builds in an underground chamber approximately 38 cm (15 in) in diameter. Woodchucks may have several burrows, generally following pathways 10-15 cm (4-6 in ) wide among them, and they may leave summer burrows in open areas to spend the winter in a burrow located in a nearby wooded area.
Food and Feeding Behavior: Herbaceous plants proved the bulk of the diet of this herbivore which may consume up to 681 g (1.5 lb) of vegetation per day. Clovers, grasses, dandelions, goldenrods, asters, and where available, alfalfa; garden crops such as corn, lettuce, peas, and beans are some of the plants the wood chuck prefers. The buds and even the barks of some deciduous shrubs and trees are spring foods, while fruits, especially raspberries, blackberries, blueberries, cherries, and apples form a part of the summer diet. Animal foods, chiefly insects, make up less than one percent of the diet. Woodchucks forage early in the morning and late in the afternoon during the summer, but mid-day in spring and autumn. Fat reserves rather than food caches supply the energy needed to sustain a woodchuck through the winter.
Activity and Movement: Contrary to the expectations of Groundhog Day, February 2, few woodchucks emerge to search for their shadows. They are more likely to leave their burrows in March, mid to late March at higher elevations. Woodchucks are mainly diurnal, i.e., active during the hours of daylight, although older males which are the first to emerge in the spring, may leave their burrows at night.
The semi-fossorial woodchuck spends most of its life in underground burrows which it excavates with stout claws, powerful legs, and sturdy incisors, the latter used to cut through roots and pry loose small stones. The extensive burrowing of this species is important in mixing the soils and in eventually providing shelters for a long list of other wildlife.
Woodchucks are conspicuous along many Adirondack roads because of the upright, alert posture they adopt periodically while active above ground, and their habit of sunbathing on logs and rocks in the spring. Woodchucks usually move by ambling along on the soles of their feet, but may run by loping or galloping at speeds of 16 km per hour (10 mph). They swim and climb well, sometimes ascending trees to heights of 15 m (50 ft), but spend most of their time on or under the ground.
Woodchucks begin hibernating in September and early October, and spend the winter curled up in the nest in an earthen chamber plugged with soil. Physiological processes slow during hibernation, e.g., the heart rate declines to 4 or 5 beats per minute from the normal rate of 80-100 beats per minute. Woodchucks lose 30-40 percent of their body weight while hibernating because of fat depletion, and emerge gaunt and thin in the spring.
Reproduction: Woodchucks breed soon after emerging in the spring and females bear one litter between late April and early June. The gestation period is 30-33 days. Females give birth to 2-9 young (average 4-5) in an underground nest. The newborn are blind, hairless, pink, each weighing 28-43 g (1.0-1.5 oz). Their eyes open at day 28, and at this age they begin to spend time outside the burrow, the females carries succulent vegetation into the burrow for her young to eat. In July and early August, the young woodchucks disperse, some digging temporary dens near the natal burrow, later establishing their home ranges in unoccupied habitat. A few may breed as yearlings, but most mature sexually as two year olds. Potential longevity is at least 6 years.
Predators: The woodchuck has many predators such as large raptors, coyotes, foxes, bobcats, raccoons, minks, black bears, and weasels.
- Social system - Woodchucks are solitary except for the family group (female and young). Males mate with one or more females, as, or soon after the females emerge from hibernation; females mate with only one male. The availability of den and feeding sites, and their respective locations influence home range size, density, and social organization. Adults defend a small territory around the burrow. Where populations are dense and portions of home ranges overlap, especially feeding sites, hierarchies may result from aggressive encounters. Thereafter, subordinates avoid dominants, and fighting is rare. Home ranges vary from 37-805 m (120-2640 ft) in diameter, the smaller ranges typical with habitat quality as well, and in optimum habitat, may reach 12.5 woodchucks per ha (5 per acre).
- Communication - Woodchucks have well-developed anal glands. Adults rub their muzzels on objects near the burrow; and adults and young press their muzzles together in “greeting” rituals. Glands located inside the corners of the mouth produce a substance with a pungent odor. Chemical cues are likely from both sets of glands. Vocalizations include “purrs”, “grunts”, “chucks”, and a shrill “whistle” given in alarm contexts (thus the colloquial names siffleur, French for whistler, and whistle-pig). Adults tooth chatter or grate their teeth in aggressive situations. Various postures serve as visual signals.
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