The animals also usually have several different places to which they can retreat during inclement weather or to avoid detection by predators. The ground-dwelling members of the squirrel family usually live in burrows. Prairie dogs and various ground squirrels live in open prairies. Marmots are most commonly seen on open grassy hillsides or meadows that may be alongside forests or in rocky areas. Some species dig their own intricate burrows, while others will use almost any available space a hole in the ground, an opening between rocks, or a hollow in a low-lying tree or stump.
Prairie dogs are communal and create large burrow systems that all members of the colony can use.
The burrow systems of marmots can be quite extensive and may have several openings to the outside. Most members of the squirrel family have one or two small litters each year. In the typical reproductive cycle of the several species of tree squirrels that have been studied, the males compete for available females. Following mating and fertilization, the gestation period lasts for about 38 to 44 days. The young are hairless and helpless at birth and are nursed by the mother.