Three species of tree squirrels are common the the Northeast Illinois region. The Eastern Gray Squirrel, the Red Squirrel and the Fox Squirrel. All are small mammals characterized by a long, bushy tail, prominent ears, and long hind feet. None of the tree squirrels hibernate, but they do have periods of reduced activity during severe cold weather. Fox and gray squirrels have similar food requirements. In fall and winter, acorns, hickory nuts, osage orange fruit and walnuts are important food sources. In winter and early spring, squirrels may eat tree buds or bark if other food is scarce. Both fox and gray squirrels cache (store) food for later use by burying it. Fox, gray, and red squirrels are diurnal meaning that they are active during the day. All tree squirrels are active year round, although they will take shelter in their nests during extreme cold weather. Like most rodents, tree squirrels have a relatively short lifespan. Most live only a year or two. Hawks, owls, foxes and coyotes all depend on squirrels as a food source.


Fox squirrels are common throughout Illinois, even in urban areas. Loss of mature, wooded habitat has decreased the population of gray squirrel in Illinois, although they remain common throughout the state and are locally abundant in urban areas. Red squirrels are found only in the northeastern part of the state, particularly along the Kankakee and Iroquois Rivers.


Each squirrel species has two breeding seasons, one in winter and the other in late spring or early summer. Female fox and gray squirrels that are at least two years old have two litters per year, younger females have only one litter per year. Average litter size is two to four, with young weaned around eight weeks of age.


Tree squirrels in Illinois are not considered to be a public health concern. They can be carriers of various parasites, but none have serious public health implications.


Squirrels are excellent climbers and jumpers. They are well known as unwelcome guests at birdfeeders. Besides consuming seed, they may damage bird and wildlife feeders by chewing on them. They may also occasionally damage lawns when caching food for the winter. They will also sometimes damage garden plants, particularly corn. While inconvenient, these behaviors can usually be handled by modifying the habitat or excluding the squirrels. In urban areas, squirrels may cause substantial property damage when they chew through siding or enlarge openings to gain access to attics. Once inside a building they may do further damage if they chew on insulation or electric wiring. Squirrels may also cause power outages when they short out transformers. It will likely be necessary to use several techniques to control property damage by squirrels. Exclusion is typically the most effective method when dealing with squirrels.