The groundhog, or woodchuck, is one of 14 species of marmots. As one of the largest members of the squirrel family, these rodents live a feast-or-famine lifestyle: They gorge themselves all summer to build up plentiful reserves of fat, then after the first frost retreat to their underground burrows to snooze until spring, drawing their sustenance from body fat. While hibernating, the animal's heart rate plunges, and its body temperature is not much warmer than the temperature inside its burrow.

Groundhog Day

Groundhog hibernation gave rise to the popular U.S. custom of Groundhog Day, held on the second of February every year. Tradition dictates that if a groundhog sees its shadow that day, there will be six more weeks of winter, though such a prediction seems a sure bet over much of the groundhog's North American range.


Groundhogs are widely distributed across North America, ranging as far south as Alabama and as far north as Alaska. They build extensive burrows—anywhere from eight to 66 feet long—with multiple entrances and rooms, including bathrooms. Some groundhogs even have more than one burrow. But these mammals tend to keep to themselves, only seeking one another out when it’s time to mate.


After roughly three months of hibernation, evidence suggests that male groundhogs wake up early to prepare for the mating season. As early as February, they leave their burrows to scope out where females are hibernating. Then they go back to sleep for another month or so until it’s time to mate.

Mating season starts in early March, ideal timing as food becomes more abundant—and there’s just enough time to start packing on the body fat they’ll need for the winter ahead.Females welcome a litter of perhaps a half-dozen newborns, which stay with their mother for several months.

Behavior and diet

Though they are usually seen on the ground, groundhogs can climb trees and are also capable swimmers. These rodents frequent the areas where woodlands meet open spaces, like fields, roads, or streams. Here they eat grasses and plants as well as fruits and tree bark. Groundhogs are the bane of many a gardener. They can decimate a plot while voraciously feeding during the summer and fall seasons.

Which Animals Hibernate?