The Vermin Reports:
13 Lined Ground Squirrels

Description

A common small mammal pest of landscapes is the thirteen-lined ground squirrel often called a striped gopher in Wisconsin and frequently confused with chipmunks. This rodent is capable of causing significant damage to turf and other landscape and garden plants as a result of its burrowing and feeding. Ground squirrels are primarily a problem in the southern 2/3 of the state.

Thirteen-lined ground squirrels are small mammals in the squirrel family (Sciuridae) that reach 4.5 - 6.5 inches in length, excluding their tail. They are brown with a whitish belly and 13 alternating light and dark stripes running the length of their back. Unlike gophers and moles, thirteen-lined ground squirrels have relatively large eyes.

Thirteen-lined ground squirrels are often confused with chipmunks but chipmunks can be distinguished by the way it carries its tail upright when running. Chipmunks have only two sets of stripes on their back and are more common around walls, wood piles and wooded areas.

Ground squirrels breed in early spring and remain active through October at which time they enter their burrow and hibernate. While active during the summer months, ground squirrels are omnivorous and have a diet consisting of seeds, roots, and insects. They can be particularly disruptive in flower beds when they dig up newly planted seeds.

Damage

Thirteen-lined ground squirrels prefer grassy areas and are most active on bright, sunny days. Population densities are usually 2-8 ground squirrels per acre however, the animals themselves are solitary. Higher populations may be found in favorable habitats such as parks and playgrounds.

Like moles and gophers, thirteen-lined ground squirrels excavate subterranean burrows. Burrows are about the diameter of a 50 cent piece. Rarely will there be excavated soil located near the entrance to a burrow. This is one way to determine whether the burrowing animal is a ground squirrel since both gophers and moles will leave excavated soil near the burrow entrance. Thirteen-lined ground squirrels have notoriously shallow borrows making them subject to flooding.

Monitoring

Thirteen-lined ground squirrels are easier to identify and monitor than gophers and moles since they are often seen poking out of their burrows, scurrying across the ground, or standing upright surveying the landscape.

Cultural Control

Any control measure implemented must be persistent since ground squirrels will readily re-infest an area from surrounding areas. Control should be initiated in the spring as soon as ground squirrels are apparent, before litters are born.

Unlike moles and gophers, thirteen-lined ground squirrels are not easily excluded from a site with the use of fencing.

Flooding the burrow with a garden hose will flush out the animal from a confined location but may not be practical on the large grassy areas in which many ground squirrels reside.

Snap traps and box traps are very effective in ground squirrel control. Locate the traps near burrows where thirteen-lined ground squirrels have been sighted. Snap-type rat traps are better for trapping adult ground squirrels than the smaller mouse trap. Mouse traps can be used in early summer along with the rat traps to trap the young ground squirrels. Bait the trap with peanut butter, grain, or nuts. Fasten nuts to the trigger to prevent the rodents from removing the bait without being caught in the trap. Check the traps frequently. To prevent injury to children, it is best to set traps when an area is not being used or when close supervision is available such as when ground crews are working in the area.

In areas where permitted, pellet guns work well to eliminate ground squirrels. It is important to use this alternative only when children are not present.

Biological Control

Thirteen-lined ground squirrels are preyed upon by hawks, snakes and a variety of mammals such as foxes, coyotes, and badgers.

Chemical Control

Rodenticides are inexpensive and effective but are a toxic means of controlling thirteen-lined ground squirrels. Zinc phosphide is registered for rodent control but is very toxic to non-target species and a restricted use pesticide at concentrations >2% which require the applicator to be certified. Anticoagulants are less harmful to non-target species particularly when the baits are placed inside the burrow. There are several varieties available at local coops or garden centers.

Source

UWEX Publication G3238 "Ground Squirrels: Their Ecology and Control" by Scott R. Craven. 4pp.