Groundhogs are not hogs at all but rodents. They are, in fact, a type of rodent called a marmot, and they are native to North America. They live in dens dug in the ground and often have one den for summer and one for winter.
Groundhogs are plump-looking animals with short tails, round ears and fur that ranges from gray to dark brown. The tips of their guard hairs are white. They weigh between 4 and 13 pounds, and are between 16 and 26 1/2 inches long on average. Males are larger than females. Groundhogs have 22 teeth, and their teeth are unusual because of their whiteness.
Groundhogs mate in the spring, and the female gives birth to up to nine pups. The mother weans the pups after about a month and a half, and the pups leave the nest when they're only about two months old. They can live six years in the wild when not felled by disease or predators.
Except for the breeding season, groundhogs are solitary. They are active during the day, when they forage. They eat mostly vegetation but also eat bird eggs and insects. During the winter in more northerly climates, groundhogs hibernate. Sometimes, they interrupt their hibernation to venture outside their den but return if it is too cold. This habit probably gave birth to the legend of Groundhog Day.