Sciuridae: Chipmunks

The eastern chipmunk keeps busy by building burrows and storing food. Photo: Steven Katovich, Bugwood.org

While the family Sciuridae also includes ground squirrels, we are focusing on two of the 15 species of native chipmunks found in North America: the eastern chipmunk (Tamias striatus) and the least chipmunk (Eutamias minimus). The eastern chipmunk is a small, brownish, ground-dwelling squirrel. It is distributed across most of the eastern half of the United States, although it is absent from Florida, most of the Carolinas and the southern half of Georgia. The eastern chipmunk is typically 5 to 6 inches long and weighs about 3 ounces. It has two tan and five blackish longitudinal stripes on its back, and two tan and two brownish stripes on each side of its face. The longitudinal stripes end at the reddish rump. The tail is 3 to 4 inches long and hairy, but not bushy.

The least chipmunk is the smallest of the chipmunks. It occurs throughout most of Canada, the U.S. Rocky Mountains, the Great Basin and parts of the Upper Midwest. It is typically 3.5 to 4.5 inches long and weighs 1 to 2 ounces. The color varies from a faint yellowish gray with tawny dark stripes (in the Badlands of South Dakota, for example) to a grayish tawny brown with black stripes (in Wisconsin and Michigan). The stripes, however, continue to the base of the tail on all least chipmunks.

Chipmunks often are confused with 13-lined ground squirrels (Spermophilus tridecemlineatus), also called striped gophers, and red squirrels (Tamiasciurus hudsonicus). The 13-lined squirrel is yellowish and lacks the facial stripes; its tail is not as hairy as the chipmunk’s. As its name implies, it has 13 stripes extending from the shoulder to the tail on each side and on its back.

The red squirrel is vocal, with a high-pitched chatter. It is larger than the chipmunk, has a bushier tail, and lacks longitudinal stripes. Red squirrels spend a great deal of time in trees, whereas chipmunks spend most of their time on the ground.

Population densities of chipmunks typically are between two and 10 animals per acre. Under good conditions, such as a suburban yard with rock gardens, oak trees, abundant low-lying vegetation and year-round bird feeders, the infestations can become severe.

The home range of a chipmunk may be up to 0.5 acre, but the adult defends a territory only about 50 feet around the burrow entrance. Although chipmunks tend to be solitary, home ranges often overlap when conditions are good.

Chipmunk burrows often are hidden near stumps, woodpiles, brush piles, basements and garages. The entrance usually is about 2 inches in diameter. There are no obvious dirt mounds around the entrance because the chipmunk carries the dirt in its cheek pouches and scatters it away from the burrow, making the entrance less obvious to predators. This behavior in itself makes the chipmunk a dangerous pest, because months or years can go by before the homeowner realizes the extent of the damage as a result of a collapsed slab or wall.

Burrow systems typically are about 25 feet in length, and normally include a nesting chamber, one or two food storage chambers, various side pockets connected to the main tunnel, and separate escape tunnels.

Chipmunks are most active during the early morning and late afternoon. With the onset of cold weather, chipmunks enter a “restless” hibernation and are relatively inactive from late fall to early March. They do not enter a “deep” hibernation like ground squirrels do; rather, they rely on the cache of food in the burrow.

Source: Truman’s Scientific Guide to Pest Management Operations, Seventh Edition, available for purchase at MyPMP.net/shop.