As herbivores, groundhogs feed mainly on green plants (clover, alfalfa, buttercups, dandelions, plantains). They are not averse to eating the bark or twigs of some shrubs and will, on occasion, consume garden fruits and vegetables as well as certain insects. They have also been known to feed on rockery flowers from time to time.
Groundhogs are sedentary and solitary creatures. Curious by nature, they climb mounds and hills to examine their surroundings. They spend long hours basking in the sun, using the rest of their time to search for food. At the slightest sign of danger, groundhogs warn each other with spasmodic, high-pitched cries, hence the name "whistle pigs." Groundhogs have excellent vision and hearing. They climb and swim with ease and, thanks to their strong forepaws, can vanish beneath the surface of any soft ground in an instant.
Groundhogs hibernate from October to March, only waking up periodically to urinate or defecate. They seldom leave their den before February and even then, only if the weather is mild enough.