Eastern Gray Squirrel Sciurus carolinensis
Eastern gray squirrels are roughly 18 inches long and 1.25 pounds. They have gray heads and backs and white or gray bellies. Some have “melanism,” an increased amount of dark pigmentation that makes them look completely black. Melanistic gray squirrels are abundant in the north and northeast, but in DuPage and other parts of the country where dense forests thinned over the centuries, the lighter color has become more advantageous for survival and, as as result, more prevalent.
Gray squirrels are active during the day year-round and eat acorns, nuts, seeds, fruits and insects, although they often bury food to eat later.
They prefer more mature woods with dense vegetation below and live in tree cavities and leaf nests, called "dreys," but may build nests in attics, garages and eaves. It's not uncommon for a squirrel to use two or more nests at the same time. Gray squirrels do not hibernate but are inactive during bad weather.
They have two breeding seasons, one in winter and one in late spring or early summer. Females under 2 have one litter a year; older females, two. Litters consist of two, three or four young, which are weaned within two months and stay near the female until the next litter is born.
Fox Squirrel Sciurus niger
Fox squirrels are the largest squirrels in Illinois. They can be 20 inches long and weigh up to 2 pounds. They're brownish gray to brownish yellow on top and brownish orange underneath.
Fox squirrels are active during the day year-round and eat acorns, nuts, seeds, fruits and insects. Like gray squirrels, they also bury food for later.
Fox squirrels live alone in tree cavities and leaf nests and build nests as well in attics, garages and eaves. One squirrel may use more than two nests at one time. They do not hibernate but will stay in their nests for days at a time when the weather's severe.
Like gray squirrels, fox squirrels have two breeding seasons, one in winter and one in late spring or early summer. Females under 2 have one litter a year; older females, two. Litters consist of two, three or four young, which are weaned within two months and stay near the female until the next litter is born.
Southern Flying Squirrel Glaucomys volans
From tip to tail, southern flying squirrels are about 10 inches long and weigh about a quarter of a pound. They have gray to brown backs and white to cream bellies and have wide, almond-shaped eyes for nighttime vision.
Flying squirrels are fairly common in Illinois, but because these animals are nocturnal, people do not often see them. They don't actually fly but glide, using a membrane between the front and hind limbs called a "patagium." As they land on trees, they'll quickly scurry to the other side to protect themselves against birds of prey.
Flying squirrels nest in natural cavities, bird and squirrel nests, nest boxes, woodpecker holes, and nests they build from leaves and twigs. Generally, though, they use cavities in winter and during the breeding season and leaf nests for resting sites and shelter. They're extremely social, too. Several will share a single nest in winter, and even in warm months four or five may use the same shelter.
Flying squirrels have two breeding seasons, one in early spring and one in summer, and have an average of four young a year. Young are weened in two months but may stay with their mother until next litter is born.