GROUND SQUIRRELS (Thirteen-Lined Ground Squirrels)
Identification
The thirteen-lined ground squirrel is a slender rat-sized rodent weighing about 8 ounces (227 g) with a length of about 10 inches (25 cm) including a tail of 3 inches (8 cm). As its name implies, 13 stripes run the length of this ground squirrel's 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 animal's eyes. The cheeks, sides of the body, and legs are yellowish, tan, 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 digging claws. There are five toes on each hind foot. Some of the common or colloquial names for this species include "thirteen-liners," "stripers," "striped ground squirrels," "striped gophers," and "gophers."
Range
The thirteen-lined ground squirrel is a grassland animal. Its original range was limited to the prairies of the North American Great Plains. When Europeans arrived and started clearing forests and establishing pastures, the thirteen-lined ground squirrel was quick to extend its range into the new habitat. Today, it ranges from central Alberta , Manitoba , and Saskatchewan in the north to Texas and New Mexico in the south, and from central Ohio in the east to Colorado in the west. The forests of the Appalachian Highlands and the Rocky Mountains have halted their east/west range expansion. There are a few colonies in Venango County , Pennsylvania , the result of introductions made in 1919.
Habitat
The thirteen-lined ground squirrel is a grassland animal. Its original range was limited to the prairies of the North American Great Plains. When Europeans arrived and started clearing forests and establishing pastures, the thirteen-lined ground squirrel was quick to extend its range into the new habitat. Today, it ranges from central Alberta , Manitoba , and Saskatchewan in the north to Texas and New Mexico in the south, and from central Ohio in the east to Colorado in the west. The forests of the Appalachian Highlands and the Rocky Mountains have halted their east/west range expansion. There are a few colonies in Venango County , Pennsylvania , the result of introductions made in 1919.
Food Habits
Thirteen-lined ground squirrels are omnivorous. At least 50% of their diet is animal matter - grasshoppers, wireworms, caterpillars, beetles, cutworms, ants, insect eggs, mice, earthworms, small birds, and each other. The vegetative portion of the diet includes seeds, green shoots, flower heads, roots, vegetables, fruits, and cereal grains. They rarely drink water, depending instead on water contained in their food. They cache large quantities of seeds and grass, but never meat. The cached food may be eaten during periods of bad weather or in the late autumn and early spring when other food is scarce.
General Biology, Reproduction, and Behavior
Thirteen-lined ground squirrels are strictly diurnal, coming above ground when the sun is high and the earth is warm, and returning to the warmth and safety of their burrows long before sundown. They rarely venture out of the burrow on damp, dark, or overcast days. When they venture out, they will often stand upright, with front paws held close to the chest, surveying their domain. If danger threatens, they run, with tail held horizontally, to the nearest burrow. The inconspicuous 2-inch (5-cm) diameter burrow opening is often concealed by vegetation and rarely has soil scattered in front of it like a woodchuck's burrow. The main entrance plunges down 6 inches (15 cm) or more before angling off into a complex system of galleries and side entranceways. The nesting chamber, about 9 inches (23 cm) in diameter and lined with fine dry grass, is located somewhat deeper than the main burrow system. The thirteen-lined ground squirrel's natural enemies include just about all predators, especially hawks, badgers, weasels, foxes, coyotes, bull snakes, and black snakes.
Thirteen-lined ground squirrels begin hibernation in September or early October and emerge between late March and early May in the northern portions of their range. In southern Texas , they have been observed above ground as late as October 27 and as early as January. Males usually begin hibernation earlier in the fall and emerge earlier in the spring than females. When they hibernate, their body temperature is generally within o C of the ambient air temperature. When active, their body temperature can vary 8 to 10o C, without ill effect.
Mating activity begins within 2 weeks after the squirrels emerge from hibernation. Both sexes are sexually active for about 2 weeks. After a gestation period of 28 days, 3 to 14 (average 10) blind, naked, and toothless young are born. Only 1 litter is produced per year. Young ground squirrels weigh about 1/10 ounce (3 to 4 g) at birth. Their stripes begin to appear after about 12 days and their eyes open 28 to 30 days after birth. Young squirrels are weaned and on their own after 6 to 12 weeks. Thirteen-lined ground squirrels are sexually mature at 9 or 10 months of age.
Damage and Damage Identification
The thirteen-lined ground squirrel's preference for insects and field mice may provide some benefit to the agricultural community. Large concentrations of these ground squirrels in pastures, fields, and gardens can, however, cause loss of forages and crops. They dig up newly planted seeds, clip emerging plant shoots, and pull over-ripening wheat, barley and oats to eat the grain. They will readily feed on commonly grown home or truck garden vegetables, often damaging much more than they consume.
Thirteen-lined ground squirrels will invade golf courses, parks, lawns, athletic fields, cemeteries, and similar wide open grassy sites. Their burrowing and feeding activity can cause major economic and aesthetic damage in such places.
Legal Status
Thirteen-lined ground squirrels are not protected by federal law. They are protected by some state and provincial regulations.
Damage Prevention and Control Methods
Exclusion
Buried galvanized hardware cloth is effective, but very expensive.
Habitat Modification
Destroy burrows and habitat by deep soil tillage. Allow growth of tall rank vegetation. Plant as early as conditions permit before squirrels emerge from hibernation. Provide alternative foods in minimum-tillage fields.
Repellents
None are registered.
Toxicants
Zinc phosphide.
Fumigants
Aluminum phosphide. Gas cartridges.
Trapping
Live traps. Glue boards. Wooden-base rat-sized snap traps. Leghold and body-gripping traps. Snares.
Shooting
Effective if persistent.
Other Methods
Burrow flooding.
ACKNOWLEDGEMENTS
The above information was adapted from PREVENTION AND CONTROL OF WILDLIFE DAMAGE with permission of the editors, Scott E. Hygnstrom, Robert M. Timm, and Gary E. Larson (Cooperative Extension Division, Institute of Agriculture and Natural Resources University of Nebraska-Lincoln, United States Department of Agriculture Animal and Plant Health Inspection Service, Animal Damage Control, Great Plains Agricultural Council Wildlife Committee).
