Marmots are large ground squirrels that have a reputation for making loud, shrill whistling sounds when they sense danger. The most widely known marmot is the groundhog, which according to tradition in the United States will emerge from hibernation on February 2 in order to prognosticate the weather.

Native to Eurasia and North America, there are 14 known species of marmots. Most of the rodents are quite bulky in size, their bodies usually extending from one to two feet long and weighing as much as 15 pounds. Marmots, which are mostly active at night, reach their highest weight in late summer or early fall because they build up fat reserves in preparation for winter hibernation. Their diet primarily consists of grasses and other green vegetation, a fact that results in their often being considered garden pests. The fur of marmots varies in color and length depending upon species and habitat. They may exhibit, for instance, various shades and mixtures of brown, red, black, gray, and white. Also, those that live in colder climes tend to have longer, thicker hair then those that live in warmer areas.

Marmots are excellent diggers, but are also capable of swimming or climbing trees, though they do not often do so. With their stocky legs and powerful claws, the rodents are capable of excavating sizeable burrows. Some marmots, like the hoary marmot, are gregarious, and may live in groups. Others, such as the groundhog, are solitary animals, except for a short period soon after the end of hibernation when they search for a suitable mate. The marmot gestation period last about a month and litters, which are born in a nesting area within the den, usually include four or five individuals.