The 13-lined ground squirrel (Spermophilus tridecemlineatus) is one of 40 species of ground squirrels in North America. They are largely a species of the Midwest and also are known as gophers, striped gophers, leopard ground squirrels, and squinneys.
Fifteen species of native chipmunks in the genus Eutamias and one in the genus Tamias are found in North America. The eastern chipmunk (Tamias striatus, Figure 1b) and least chipmunk (Eutamias minimas, Figure 1c) are the most widely distributed species.
Chipmunks and 13-lined ground squirrels are unprotected by federal law but may be protected by some state and provincial regulations. Most states allow landowners or tenants to capture and kill chipmunks when they are causing or about to cause damage. Some states (e.g., Georgia and Arkansas) require a permit to kill non–game animals. Other states are developing laws to protect all non–game species. Consult local and state regulations before enacting control.
Thirteen-lined ground squirrel
As the name implies, 13 stripes run the length of the body. Five of the light-colored lines break up into a series of spots as they progress down the back and over the rump. Five light and four dark stripes extend along the top of the head and end between the eyes. The cheeks, body, and legs are yellow or tan, with an orange cast. The chest and belly are thinly covered with light tan fur. Each front foot has four toes with long, slender claws. Five toes occur on each hind foot. Some of the common names include “13-liners,” “stripers,” “striped ground squirrels,” “striped gophers,” and “gophers.” Thirteen-lined ground squirrels weigh about 8 ounces. They grow to a length of about 10 inches, including a tail of 3 inches.
Eastern chipmunks are small, brown, ground-dwelling squirrels. They are 5 to 6 inches long and weigh 3 ounces. Two tan and five black longitudinal stripes occur on the back, and two tan and two brown stripes occur on each side of the face. The stripes end at the rump. The tail is 3 to 4 inches long and hairy.
Least chipmunks are the smallest of the chipmunks. Typically, they are 3 to 4½ inches long and weigh 1 to 2 ounces. Color varies from yellow–gray with tawny dark stripes (Badlands, South Dakota) to gray-tawny-brown with black stripes (Wisconsin and Michigan). The stripes continue to the base of the tail.
Chipmunks often are confused with 13-lined ground squirrels and red squirrels (Tamiasciurus hudsonicus). When startled, a ground squirrel carries its tail horizontally along the ground; chipmunks carry their tails upright. Red squirrels are larger than chipmunks, have bushier tails, and lack longitudinal stripes. Red squirrels spend a great deal of time in trees, while chipmunks spend most of their time on the ground, although they can climb trees.
The original range of 13-lined ground squirrels was in the prairies of the North American Great Plains. When Europeans started clearing forests and establishing pastures, 13-lined ground squirrels extended their range into the new habitat. Today, they range from Alberta, Manitoba, and Saskatchewan in the north to Texas in the south, and from central Ohio in the east to Colorado in the west (Figure 2a). A few colonies occur in Venango County, Pennsylvania, where they were introduced in 1919. The range of eastern chipmunks includes most of the eastern US (Figure 2b), excluding the southeastern coast and Florida. The range of least chipmunks (Figure 2c) includes most of Canada, the US Rocky Mountains, the Great Basin, and parts of the upper Midwest.
Figure 2a. Distribution of the 13-lined ground squirrel in North America.
Image by Prevention and Control of Wildlife Damage (PCWD).
Figure 2b. Distribution of the eastern chipmunk in North America.
Image by PCWD.
Figure 2c. Distribution of the least chipmunk in North America.
Image by PCWD.
Tracks and Signs
It is rare to find tracks of 13-lined ground squirrels (Figure 3) or chipmunks. Squirrels normally are identified by entrances to dens or visual sightings. Chipmunks usually are quite noticeable, as they are active during daylight hours.
Voice and Sounds
Thirteen-lined ground squirrels exhibit six different calls. The call that is most commonly heard is a high-pitched trill that is used to signal danger. However, 13-lined ground squirrels do not consistently use warning calls.
Chipmunks vocalize a sharp “chuck-chuck-chuck” call. Their warning call is a high pitched “wee,” which commonly is heard when perceived danger approaches.
Figure 3. Tracks of a 13-lined ground squirrel.
Image by Dee Ebbeka.