Thirteen-lined ground squirrels are small and slender rodents, with alternate stripes of dark brown and tan, extending from the neck to the tail. The dark brown stripes are wider than the tan stripes, and have tan rectangular spots along the midline. These stripes are where the thirteen-lined ground squirrel got its name. The "thirteen lines" consist of either seven broad dark brown stripes alternating with six thin tan bands or seven narrow yellow stripes alternating with six broader dark brown stripes.
The ears are short, and the tail is thin and sparingly bushy. This squirrel often sits erect with nose pointed up. Males and females are similar in appearance. Total length ranges from 170 to 310 mm, with the tail making up from 60 to 132 mm of that. Weight ranges from 110 to 140 grams in the spring but these squirrels may double their weight just before entering hibernation in the winter.
Thirteen-lined ground squirrels are native to the Nearctic region and found in central North America. Originally confined to the prairie, they have extended their range northward and eastward over the past two centuries as land has been cleared. Currently they can be found as far east as Ohio and as far west as Montana and Arizona. They are found as far north as central Alberta and Saskatchewan and are as far south as the Texas coast.
Thirteen-lined ground squirrels prefer open areas with short grass and well-drained sandy or loamy soils for burrows. They avoid wooded areas. Mowed lawns, golf courses, cemetaries, well-grazed pastures, parks and roadsides are also common habitats.
Up to 90% of newborns die from predation before hibernation begins. Once they have reached adulthood Thirteen-lined ground squirrels probably live for only a few years.
Thirteen-lined ground squirrels are diurnal and most active at midday and on warm sunny days. They dig shallow emergency burrows that do not go anywhere, but stop ina dead end. They also build complex deeper underground burrows used for nesting and hibernation. These squirrels are not colonial but may live close to others in a small area because of access to good habitat. There are usually 1 to 20 animals per acre depending on the season. Home burrows are defended.
In the fall, thirteen-lined ground squirrels rapidly gain weight (up to 4 gm fat per day) to prepare for winter hiibernation. They hibernate in underground burrows from August through March. They are true hibernators, allowing their body temperature to drop to just above freezing and their heart rate to drop to as low as 20 beats per minute from their usual 200. During hibernation, they can lose up to 1/3 of their body weight. Stored up food is consumed during hibernation breaks, especially just before emergence.
Thirteen-lined ground squirrels have excellent senses of vision, touch, and smell. They use alarm calls and other sounds, as well as using special scented secretions, to communicate with other squirrels. They rub glands around their mouth on objects to leave scent marks. They also greet one another by touching noses and lips.
Thirteen-lined ground squirrels are omnivorous. Their genus name, Spermophilus, means "seed lover," and these squirrels eat the seeds of weed plants as well as available crop species like corn and wheat. They will eat the leaves of grass and clover. They will also store plant material underground, transporting it in cheek pouches. They also consume animal matter, such as insects, occasional small vertebrates, bird eggs, and carrion.
Thirteen-lined ground squirrels give alarm calls when they sense the presence of a predator, then all surrounding squirrels escape into their burrows. Main predators include snakes and hawks, such as red-tailed hawks and Cooper's hawks.
Thirteen-lined ground squirrels impact plant communities by eating seeds and foliage. They act as important prey bases for small predators, such as weasels, raptors, and snakes, and help to recycle soil nutrients through their burrowing activities. They also play host to many ectoparasites including fleas, lice, mites, ticks and to endoparasites.
Consumes agricultural crops like corn, wheat, oats and sunflowers although the damage is limited to the harvest season, not during winter storage.
This animal has been expanding its range from the prairie states northward and eastward as land is cleared for human building and agriculture.
Previously known as Citellus tridecemlineatus.
Sally Petrella (author), University of Michigan-Ann Arbor.
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