Groundhogs, also called Woodchucks, are in the Squirrel family, Sciuridae. They are the largest vertebrates in the Squirrel family.
Woodchucks hibernate in the winter and come out of their burrows in the spring when they mate and have their offspring. They are most active in the morning and then in the late afternoons when they are foraging for vegetation.
Check with your local authorities regarding control of Woodchucks in your area as some states and counties they are protected. And as with any pest control program, know and use the appropriate personal protection as some Woodchucks have been found to carry the plague.