Groundhog

Name and taxonomy

Carl Linnaeus named the species Mus monax in 1758. He worked from a description that George Edwards published in 1743. The species later moved into the marmot genus, Marmota, within the squirrel family Sciuridae. Monax is an Algonquian word that means digger. Nine subspecies are recognised, and GBIF lists four of them by name.

The name woodchuck has nothing to do with wood or with chucking. It comes from an Algonquian name for the animal, wuchak, possibly from the Narragansett language. The likeness of the two words gave rise to the tongue-twister about how much wood a woodchuck could chuck. Other names include groundpig, whistler, thickwood badger, Canada marmot, land beaver and, in French Canada, siffleux. Young groundhogs are sometimes called chucklings.

Evolution and relatives

The groundhog is a rodent of the order Rodentia and a ground squirrel of the family Sciuridae. It is one of 14 marmot species, and the most widespread marmot in North America. Its closest relatives include the hoary marmot and the yellow-bellied marmot of the western mountains. Those species live among rocks at high altitude, while the groundhog stays in the lowlands. In British Columbia the two ranges meet, and the hoary marmot there is a little larger.

Groundhogs are thought to be the least social of the marmots. Like other marmots, they are true hibernators, and they carry 38 chromosomes. Groundhog bones have turned up in ancient mounds at Aztalan in Wisconsin.

Appearance

The groundhog is stocky, with short strong legs, long broad claws and a short bushy tail. Adults weigh 2 to 6 kilograms, and the tail adds 10 to 16 centimetres to a total length of 41.5 to 67.5 cm. Males average about 3.83 kg over the year and females about 3.53 kg. Every animal is far heavier in autumn than in spring, because it lays down fat for the winter. Weight climbs during the first two or three summers of life and then levels off.

The coat runs from grey through cinnamon to dark brown. Pale tips on the guard hairs give it a frosted, grizzled look. The paws are usually black or dark brown, the tail is dark, and pale patches surround the snout and chin. The tail is about a quarter of the body length, shorter than in other squirrels.

The four incisors are white rather than the orange of most rodents. They grow about 1.5 millimetres a week, and chewing wears them down at the same rate. The groundhog has 22 teeth in all. Its rounded ears can close over the ear canal, which keeps soil out while it digs.

Habitat and range

The groundhog ranges from Alaska across southern Canada to Labrador and south through the eastern United States. Its southern limit runs from eastern Oklahoma and northern Louisiana through Alabama and Georgia to North Carolina. It also reaches down the Rocky Mountains, possibly as far as northern Idaho. GBIF holds records from 7 countries, which include a few animals outside the native range.

It prefers open country next to woodland, and it rarely strays far from a burrow entrance. Typical homes are small woodlots, low forests, fields, pastures, orchards, hedgerows and roadsides. It also lives in urban parks and under buildings and bridges. Cleared forest, roads and farming have given it more food, so it has spread with people.

It digs its burrows in well-drained soil. Most animals keep a summer den near food and a separate winter den near cover. A burrow usually has two to five entrances, one of them a spy hole. The longest burrow measured ran 7.3 metres, or 14.62 metres when its side galleries were counted.

Diet and feeding

The groundhog is mostly a plant eater. It grazes on wild grasses, clover, alfalfa, dandelion and coltsfoot, and it takes berries, leaves, bark and crops. Now and then it eats grubs, grasshoppers, snails, bird eggs and nestlings. It climbs trees for leaves, fruit and soft seeds. It gets most of its water from plant juices and from rain or dew on the leaves.

An adult can eat more than 0.45 kilograms of plants in a day. It usually feeds twice a day in summer, in the morning and in the afternoon. Each feeding bout lasts less than 2 hours. From early June its metabolism slows, and it can double its weight as it stores fat. It does not store food in the burrow, because the fat carries it through the winter.

Behaviour and social life

The groundhog is active by day, most of all in the early morning and the late afternoon. In towns it may also move about at dusk or at night. It often sits upright on its hind feet and stays nearly still while it watches for danger. When a threat appears it runs for the burrow, and it will fight with teeth and claws if the burrow is invaded. It swims well, and it climbs a tree when chased or when it wants a better view.

Adults live alone and defend a territory. A dominant male holds a home range of about 10,000 square metres, which overlaps the ranges of two or more females. A female uses about 2,500 square metres in spring, and more after her pups are born. Young males without a territory wander. Meetings between adults are usually hostile, though close relatives are a little more tolerant.

Groundhogs are true hibernators, and many dig a separate winter burrow below the frost line. In most areas they sleep from October until March or April, but in mild regions the sleep can last only three months. Body temperature falls to about 2 degrees Celsius, the heart slows to 4 to 10 beats a minute, and one breath comes every six minutes. By February a hibernating groundhog may have lost half its body weight. Males wake before females and set up territories before the females appear.

Communication and senses

Sight, smell and sound all matter to the groundhog. It relies on its eyes to spot predators and to threaten rivals. Glands on the face and near the anus produce scent, which it rubs on stumps and rocks to mark its ground. A threatened animal arches its body, bares its teeth and raises its tail.

The best-known call is a shrill whistle, given when danger is near. That alarm warns other groundhogs, especially the young, and it gave the animal the name whistle-pig. It also hisses, growls, barks, shrieks and chatters its teeth. A groundhog squeals when it fights, when it is badly hurt, or when a predator catches it. On the rare occasions when two meet peacefully, they may touch noses.

Reproduction and life cycle

Groundhogs are polygynous, and a male mates with several females in a season. Mating comes soon after hibernation ends, from early March to late April, and later in the north. A female comes into heat once a year. The pair may share a den during the 31 to 32 days of pregnancy, and the male leaves before the birth. In Ohio, some males and females stay together through the year and from year to year.

A female bears one litter a year, of 1 to 9 pups, most often 3 to 5. A newborn weighs 26 to 27 grams and is blind and naked. The mother does all the rearing. The pups nurse for about 44 days. They leave the burrow at five to six weeks, once their fur has grown and their eyes are open. They are independent at about 2 months, and most scatter to dig their own burrows by the end of August.

Most groundhogs first breed at 2 years old, though some yearlings breed with less success. They keep growing for two to three years. A wild groundhog lives 4 to 6 years, and a captive one has reached 14. Many die before their third year from predators and disease.

Predators and threats

Coyotes, red foxes, grey foxes, bobcats and badgers take adult groundhogs across eastern North America. Most of these hunters stalk and surprise a groundhog before it can reach its burrow. Badgers probably dig them out. In one Pennsylvania study the groundhog was the third most important prey of the coyote. Wolves, black bears, lynx and cougars take some in Canada.

Young groundhogs also fall to mink, cats, hawks and timber rattlesnakes. Red-tailed hawks catch animals up to yearling size, and goshawks take some young adults in spring. Golden eagles and great horned owls can kill an adult but seldom meet one. Near towns the main killers are people, dogs and cars.

Groundhogs carry botflies, ticks, fleas and mites, and some die from parasites or the bacteria they spread. A share of the population carries the woodchuck hepatitis virus, which harms the liver. They can also carry tularemia and rabies.

Population and conservation

The IUCN lists the groundhog as Least Concern. It is abundant, its range is wide, and its numbers are stable. Forest clearance and farming have helped it, and it thrives near people. No one appears to have counted the whole population.

Local numbers can still fall under heavy hunting. In the dairy country of southern Wisconsin the species was nearly wiped out by 1950 after exaggerated reports of crop damage. Wisconsin then protected it until 2017. Kentucky hunters took an estimated 267,500 a year between 1964 and 1971. Numbers appear to have dropped in Illinois.

Relationship with humans

Farmers and gardeners see the groundhog as a pest. It eats vegetables, hay, cereals and orchard fruit. Its holes can break farm machinery, injure livestock and, over many years, weaken a foundation. A New Hampshire committee report of 1883 called the woodchuck a nuisance and a bore.

In many states the groundhog is a game animal, hunted for sport, meat and fur. In parts of the United States people have long eaten it, and some still call it a delicacy. Its burrows at the Ufferman Site in Ohio brought bones, pottery and stone tools to the surface for archaeologists.

Groundhogs matter in medicine, because the woodchuck hepatitis virus resembles human hepatitis B. The virus cannot infect people, so the groundhog is the main animal model for liver cancer caused by hepatitis. Researchers also study its hibernation in the hope of slowing a patient's heart during surgery. In captivity it stays aggressive, and a zookeeper has to work hard to tame one.

In culture and myth

In the United States and Canada, Groundhog Day falls on 2 February. If the groundhog sees its shadow, the story says, six more weeks of winter are thought to follow. The custom is thought to descend from European Candlemas lore, in which Pennsylvania German settlers swapped the badger for the groundhog. Punxsutawney Phil in Pennsylvania is the most famous forecaster, alongside Buckeye Chuck, Wiarton Willie, Shubenacadie Sam and Staten Island Chuck. The 1993 comedy film Groundhog Day put Phil and his ceremony on cinema screens.

The Algonquian names monax and wuchak show how long the animal has been part of North American life. In Ojibwe tradition, symbolism writers suggest, a groundhog clan is tied to healing. Robert Frost's poem A Drumlin Woodchuck uses a groundhog dug into a ridge as a picture of his own reserve. The tongue-twister about the woodchuck chucking wood is the animal's best-known line in English.