Spermophilus tridecemlineatus is found in central North America. Originally confined to the prairie, it has extended its range northward and eastward over the past two centuries as land has been cleared. Currently S. tridecemlineatus can be found as far east as Ohio and as far west as Montana and Arizona. It reaches its northern limit in central Alberta and Saskatchewan and is found as far south as the Texas coast.
Spermophilus tridecemlineatus prefers open areas with short grass and well-drained sandy or loamy soils for burrows. It avoids wooded areas. Mowed lawns, golf courses, cemetaries, well-grazed pastures, parks and roadsides are common habitats for it now that it is no longer limited to prairie regions. (Jones 1988, Kurta 1995)
total body length: 225 to 300 mm tail length: 75 to 109 mm
Spermophilus tridecemlineatus is a small slender ground squirrel with alternate longitudinal stripes of dark brown and tan, extending from the nape to the base of the tail. The dark brown stripes are broader than the tan lines and have tan rectangular spots along the midline. The "thirteen lines" consist of either (1) seven broad dark brown stripes alternating with six thin tan bands or (2) 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 head pointed up.
The skull of Spermophilus tridecemlineatus is sciurognathous and sciuromorphous, meaning that the lower jaw is v-shaped and that there is a large zygomatic plate anterior to the orbit where the lateral masseter arises. The infraorbital foramen is small and shifted forward. A postorbital process is present. The dental formula is 1/1, 0/0, 2/1, 3/3. Like all rodents, S. tridecemlineatus lacks canines, has evergrowing incisors with enamel only on the front and sides, and has a large diastema separating incisors and cheek teeth.
(Kurta 1995, Jones 1988, Palmer 1995, Lawlor 1979)
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 blind-end emergency burrows as well as complex deeper underground burrows used for nesting and hibernation. These squirrels are not colonial but may concentrate in one area with desirable substrate. Home ranges are 4.7 ha. for males and 1.4 ha. for females. Density ranges from 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 dormancy. 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, S. tridecemlineatus can lose up to 1/3 of its body weight. Food caches are consumed during hibernation arousals, especially just prior to emergence.
Thirteen-lined ground squirrels are important prey species for carnivores, raptors and snakes. They also play host to many ectoparasites including fleas, lice, mites, ticks and other endoparasites. They molt twice yearly.
(Jones 1988, Kurta 1995, Palmer 1995, Livoreil 1996)
In the spring, males arise from hibernation before the females and soon begin their search for available females to breed. A male copulates several times with a female before leaving to search for other females. Seventy five percent of each litter is sired by the first male to breed the female. There is no post-copulatory guarding behavior. Males breed with one female until they have successfully bred for over 9 minutes. A delay between breeding by other males and a long copulatory duration are correlated with breeding success for specific males.
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.
Spermophilus tridecemlineatus is omnivorous. Spermophilus means "seed lover," and this squirrel eats the seeds of weed plants as well as available crop species like corn and wheat. It will eat the leaves of grass and clover and hoardes plant material underground, transporting it in cheek pouches. Animal matter consumed includes insects, occasional small vertebrates, bird eggs and carrion. (Kurta 1995, Palmer 1995)
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.
Previously also known as Citellus tridecemlineatus (Long 1994).
Sally Petrella (author), University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
flesh of dead animals.
uses smells or other chemicals to communicate
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
union of egg and spermatozoan
Referring to a burrowing life-style or behavior, specialized for digging or burrowing.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
an animal that mainly eats all kinds of things, including plants and animals
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
places a food item in a special place to be eaten later. Also called "hoarding"
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
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.