So far as I know, the groundhog is the only rodent to have its own official day. It also has its own song, an old southern Appalachian banjo tune about an epic hunt. It is only fitting for banjo players to sing about groundhogs–or whistle pigs, an alternative name that shows up in some versions of the song–since groundhog hide was commonly used to make the heads of homemade banjos.

The groundhog has other names as well. Woodchuck is the most common. This name has fed endless speculation on the amount of timber a groundhog would hurl if it was capable of throwing logs around. The question, as so often in philosophy, resolves itself into a semantic argument. “Woodchuck” is actually a corrupted version of Cree or Chippewa words that sound something like “wuchak” or “otchig.” These words have nothing to do with either lumber or throwing. For that matter, they have nothing to do with woodchucks. They actually describe another small mammal, the fisher. However, since nobody but some of Cecil Adams’s daffier correspondents would wonder how much wu a wuchak would chak if a wu chak could chak wu, we may consider this conundrum settled.

You may think I am about a month late in writing about woodchucks, since Groundhog Day is traditionally celebrated on February 2. But the fact is, Groundhog Day is far too early. In most of this animal’s range, it is sunk in deepest slumber in early February. March is a far more likely month for groundhog emergence in Illinois.

Still, it is at least possible that a woodchuck might awaken from hibernation and take a look around in February. For reasons unknown, even the deepest hibernators wake up from time to time during the winter. Some species of ground squirrels store food in their burrows and periodically get up to eat. Woodchucks do not store any food, but some scientists think they get up to pee, since urination is an almost invariable action of an awakened woodchuck.

The general consensus among woodchuck students is that there must be an important reason for the animals to get up. Coming out of hibernation uses large amounts of energy–the process takes about three hours–so selection pressure would probably act against it if it didn’t offer some compensating advantage.

Hibernation is a strategy for conserving energy, for riding out difficult times with a minimum expenditure. There are all sorts of variants of this strategy. Physiologists who study it usually reserve the term “hibernation” for really deep slumbers. The less extreme forms are called “torpor.” Torpor can be very slight and short-lived. Camels and some other desert mammals can reduce their body temperatures slightly during the cold desert night and raise them back up in the morning.

Bears experience torpor rather than true hibernation. In winter a black bear has a rectal temperature of 90 to 95 degrees Fahrenheit. Its heart rate is about 10 to the minute, compared to 40 a minute for a sleeping bear in summer, and its overall metabolic rate is 50 to 60 percent of summer levels. Bears can awaken quickly from this state, so one must admire the bravery of the biologists who obtained those rectal temperatures. Wouldn’t it be great if Bill Kurtis would do a show on these people? Can’t you imagine Bill, thermometer in hand, creeping up on a snoring bear while maintaining a constant whispered voice-over?

An animal is not considered a true hibernator unless its body temperature drops below about 40 degrees. This sort of profound slumber is most highly developed among the rodents, especially the Sciuromorphs, the group that includes squirrels and woodchucks. As it happens, the woodchuck is the largest true hibernator in existence. When it lies down in October or November, its heart rate begins to get slower. It may skip beats as it slows down. Next oxygen consumption declines, and finally body temperature. Once it is fully in its winter sleep, its body temperature drops from a summer level of 97 degrees to hover just a few degrees above freezing. Its heart slows from about 80 beats a minute to about 4. Its breathing rate slows from 25 to 30 breaths per minute to about 1 every five minutes. It is living on the fat reserves it built up during the summer, but it is not using them very fast.

This turns out to be very helpful to the animal. When it emerges from its slumbers in early spring, most plants will still be dormant. There will be no new growth of leaves yet and certainly no flowers or fruits. Woodchucks have to get by on dried stuff left over from last year and on bark.

They need energy right away because reproduction is the spring’s first activity. Woodchucks are generally solitary animals. Each one digs a large and ramified burrow system that usually has at least two entrances and may have as much as 75 feet of interconnected tunnels. Within the burrow will be one or more nests, areas where the tunnel is widened and deepened. These nests may be as much as five feet underground, which puts them well below the frost line. These nests are hibernacula, nurseries, and sleeping areas. Woodchucks also dig a separate defecation chamber in the burrow.

In spring a male woodchuck will move into a female’s burrow for a brief time. This is the only portion of the year when the adults depart from their usual solitary mode of life. The young are born in April after a 32-day gestation period. An average litter consists of four or five animals. They weigh about an ounce at birth, and they are naked, blind, and helpless. They don’t open their eyes until they are about a month old, and they don’t go above ground for another couple of weeks after that.

Food has to be the major interest of young woodchucks. Between April and November they have to grow from one ounce to about six pounds in order to sleep comfortably through their first hibernation. They won’t reach full adult size until their second year, when the males will average close to nine pounds each. The females will be slightly smaller. Woodchucks have been known to weigh as much as 14 pounds.

They achieve this impressive size on a diet of grasses, clovers, leaves, fruit, and bark. They feed mostly on the ground, although they can and do climb trees when they need to. According to various studies, they are able to get enough to eat while feeding only a few hours a day. Even in summer they spend most of their time in their burrows.

Woodchucks are easily recognized. They are thick-bodied animals, much chunkier than squirrels. Their ears are short and rounded. Their fur is reddish brown tipped with white, a combination that produces a grizzled appearance. Their tails are thick and bushy, but not nearly as long as a tree squirrel’s.

You can see woodchucks in lots of places. If you get out in the country, you may see them along country roads. The few hours they spend above ground are always in the daylight. They seem to want to take advantage of the little chance they get to absorb some rays, so you’ll often see them just sitting in the sun. When they see you, they may give a loud whistle before heading for their burrows.

Woodchucks benefited from the changes in the Illinois landscape that accompanied settlement. Robert Kennicott, writing in 1857, noted that they had been rare in northeastern Illinois in the past, but they were then becoming quite common. They are edge animals. You can often find their burrows where woodlands meet grasslands. You probably would not have found them on the unbroken prairie.

The entrances to burrows are large–up to a foot across–and there is likely to be a large heap of earth next to the entrance. In late summer when the grass is tall, trails radiating out from the burrow entrance may mark the customary paths the woodchucks follow to get to feeding areas.

Woodchuck burrows have some importance to the ecosystem. Other animals–rabbits, skunks, opossums, even foxes–use them for shelter. In building the burrows the woodchucks also help turn over the soil, bringing minerals up from the subsoil and depositing–especially in those defecation chambers–organic matter deep below the surface. Somebody once calculated that woodchucks in the state of New York rearranged 1,600,000 tons of soil every year.

In the Cook County forest preserves, woodchucks are likely to be hanging around the borders between woodlands and open fields, and they’re more likely to be out in the middle of the day than at sunrise or sunset.