Chipmunks

The eastern chipmunk, Tamias striatus, one of Illinois’ smaller mammals, is quite active in our area  from late spring until mid-autumn.  Chipmunks are abundant throughout Illinois, and they are one of four species of ground squirrels that also includes the thirteen-lined ground squirrel, the Franklin’s ground squirrel and the woodchuck.  Chipmunks are the smallest of the four, weighing from two to five ounces and growing eight to twelve inches in length.  They have alternating dark and light stripes on their backs, sides, and cheeks; light bellies; small, erect ears; and furry, flattened tails. 

A chipmunk’s eyes are located on the sides of its head and provide excellent ninety-degree views from directly in front of their face around to both left and right sides.  They can easily detect any nearby motion and moving shadows cast by birds or any other overhead object.  Chipmunks have a poor sense of smell, but an excellent sense of hearing.  They climb trees to escape predators and to search for food.  Their fur is reddish-brown on top and a buff colored below, making them hard to see from overhead or underneath when they are up in the trees.

After finding a mate, chipmunks construct an underground nest of extensive tunnels and chambers using their noses and clawed feet.  A work tunnel is started by digging a well-hidden entrance hole followed by a wider tunnel leading to a large, centrally located nest chamber lined with leaves.  Several smaller chambers are dug for food storage.  A second exit hole is handy for emergencies, and several tunnels extend downwards to draw water away from the main tunnel system.  Nests are often re-used each winter, adding many tunnels and chambers through annual remodeling.

Mated chipmunks will enter their nest in mid-November and stay together underground until late March.  Chipmunks do not accumulate bodily fat reserves and do not hibernate.  They can reduce their metabolic rate by 85% during sleep periods lasting from three to seven days.  Awake for one to two days between sleep periods, they restore energy by eating from cached food supplies.  Mating occurs in early spring followed by a 31-day gestation period.  Two to eight hairless and completely dependent young are born in late April.  The male chipmunk may leave the nest in spring, leaving the female to handle all rearing of the young,  which are weaned at about six weeks.

Chipmunks have cheek pouches used for gathering food.  These extend from the mouth down either side of the neck and are expandable, carrying up to two tablespoons of seeds and grass.  Food may include seeds, nuts, fungi, bulbs, moles, grasshoppers, small frogs, salamanders, and bird eggs.  Cheek pouches reduce the number of excursions outside the nest needed to fill food caches.  However, they usually do not carry a maximum load because they still need to fit their head through their tunnel opening of about two inches in diameter.  They find water in fallen leaves or small pools and will drink as much as 25% of their weight daily.

Chipmunks are common visitors to woodlands and backyards where food is easily found.  When danger is nearby, they immediately freeze all movement and can hold their position for several minutes.  When the tail is held upright, this is a signal of danger nearby.  When establishing or defending territory, they will stomp their feet and swish their tails.  Chipmunks take frequent dust baths to remove mites, fleas and other bugs from their fur.  Active mainly in the early morning and late afternoon, they are fun to observe, especially when exhibiting their unique behaviors.