What do they look like?

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.

Where in the world do they live?

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.

What kind of habitat do they need?

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.

How do they reproduce?

After mating, female ground squirres remain pregnant for 28 days. Between 6 and 13 young are born at the same time, with an average of 8-9 young. This group of babies is called a litter.

The young are born blind, hairless, and toothless and weigh 4 g. They are nursed and cared for in the burrow by their mother. The young gain 1.3 g each day, open their eyes at day 13, leave the burrow for the first time at 28 to 35 days, and are full grown in 90 days. At six weeks old, members of the litter begin digging their own burrows, usually within 100 m of where they were born.

How long do they live?

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.

How do they behave?

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.

How do they communicate with each other?

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.

What do they eat?

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.

What eats them and how do they avoid being eaten?

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.

What roles do they have in the ecosystem?

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.

Do they cause problems?

Consumes agricultural crops like corn, wheat, oats and sunflowers although the damage is limited to the harvest season, not during winter storage.

Are they endangered?

This animal has been expanding its range from the prairie states northward and eastward as land is cleared for human building and agriculture.

Some more information...

Previously known as Citellus tridecemlineatus.

Contributors

Sally Petrella, University of Michigan

References

Jones, J.K. Jr. 1988. Handbook of Mammals of the North Central States. University of Minnesota Press, Minneapolis, MN.

Kurta, A. 1995. Mammals of the Great Lakes Region. Fitzhenry and Whiteside, Toronto, Ontario.

Lawlor, T.E. 1979. Handbook to the Living Orders and Families of Mammals. Mad River Press, Eureka, CA.

Livoreil, B. and C. Baudoin. 1996. Differences in Food Hoarding Behavior in two Species of Ground Squirrels Spermophilus tridecemlineatus and S. spilosoma. Ethology Ecology and Evolution 8: 199-205.

Long, C.A. 1974. Environmental Status of the Lake Michigan Region. Volume 15. Mammals of the Lake Michigan Drainage Basin. Argonne National Laboratory, Argonne, IL.

Palmer, E.L. and H.S. Fowler. 1995. Fieldbook of Natural History. Second edition. McGraw-Hill, Inc., NY.

Schwagmeyer, P.L. and G.A. Parker. 1994. Mate-quitting Rules for Male Thirteen-lined Ground Squirrels. Behavioral Ecology 5(2): 142-150.