Ground squirrels range in size from the small pygmy squirrels, which are only 3 to 4 inches in size, to larger varieties that can reach up to a foot in size. The ones commonly seen in most parts of the United States typically are 7 to 8 inches and weigh just under a pound when they reach adulthood. They eat grains, nuts, seeds and grasses but will also eat scraps of human food if they come across them. They can carry extra food in cheek pouches and will take some into their burrows to store for later.
Burrowing ground squirrels usually dig numerous holes to get in and out of their burrows. The burrows are where they live, sleep and hibernate. They also run into their burrows when frightened or threatened. In cold-weather climates, the squirrels may hibernate for four to six months. In warmer climates, the squirrels will not actually hibernate but will remain underground in their burrows for extended periods, surviving on stored food. Some varieties also estivate, or sleep for periods of several weeks at a time, during the summer months.
The burrows of some varieties of ground squirrels are surprisingly complex. The burrows consist of "rooms" for sleeping and eating; some even have what in a human home would be a bathroom. The rooms are connected to each other by tunnels, with three to five outlets to the surface. There are also separate rooms in which individual squirrels hibernate. In most ground squirrel species, the adult females "own" the burrows; each has at least one but sometimes more burrow systems. These complexes can be as deep as 6 feet under the surface and may extend as far as 40 feet.
Most of the problems caused by burrowing squirrels are of the nuisance variety---piles of dirt in your yard or garden, for example. Some are more serious, however. Certain varieties of ground squirrels come up at night and eat eggs from birds' nests, seeds recently sown for crops and the seedlings or sprouts of farm crops. Others have been known to carry infectious diseases that are harmful to humans. The burrow systems themselves may also cause problems, ranging from the tripping hazards caused by the entrance holes to land subsidence and permanent erosion of sub-surface soil.