Family Sciuridae: (Squirrels) - Squirrels are medium-sized, mostly diurnal (active in the daytime) mammals. There are four toes on each front foot and five toes on each back foot. The tail is hairy. Some squirrels are arboreal (tree-dwellers), and some live on the ground.
     eastern chipmunk (Tamias striatus)
     woodchuck (Marmota monax)
     thirteen-lined ground squirrel (Spermophilus tridecemlineatus)
     Franklin's ground squirrel (Poliocitellus franklinii) [Illinois threatened]
     eastern gray squirrel (Sciurus carolinensis)
     eastern fox squirrel (Sciurus niger)
     red squirrel (Tamiasciurus hudsonicus)
     southern flying squirrel (Glaucomys volans)