Wow, I never heard of a ground squirrel before and would not have thought of a groundhog!
According to wikipedia, "ground squirrel" is a totally generic term that covers a rather large number of related грызуны (rodents).

The group includes prairie dogs (луговые собачки, lit. "meadow dogs"); chipmunks (бурундуки); marmots (сурки); susliks (суслики), and others -- although they come in very different sizes and have different lifestyles.

The American "groundhog" (aka "woodchuck") -- as seen in rockzmom's photo -- technically belongs to the "marmot" sub-group of ground-squirrels, and is called a лесной сурок ("forest marmot") in Russian.

And, by the way, although the name "woodchuck" seems to mean "one who chucks wood" (тот, кто бросает или выбрасивает дерево), it actually comes (via "false folk etymology") from a native Algonquian term for the animal -- wutchak.

P.S. Thanks, wikipedia!