Spermophilus tridecemlineatusthirteen-lined ground squirrel

Last updated:

Geographic Range

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.

Habitat

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)

Physical Description

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)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    110.0 to 140.0 g
    3.88 to 4.93 oz
  • Range length
    170.0 to 310.0 mm
    6.69 to 12.20 in
  • Average length
    250.0 mm
    9.84 in
  • Average basal metabolic rate
    0.983 W
    AnAge

Lifespan/Longevity

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.

  • Average lifespan
    Status: captivity
    7.9 years
    AnAge

Behavior

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.

(Schwagmeyer 1994)

Communication and Perception

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.

Food Habits

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)

  • Animal Foods
  • eggs
  • carrion
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • leaves
  • roots and tubers
  • seeds, grains, and nuts
  • fruit

Predation

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.

  • Known Predators

Ecosystem Roles

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.

Economic Importance for Humans: Negative

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

  • Negative Impacts
  • crop pest

Conservation Status

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

Other Comments

Previously also known as Citellus tridecemlineatus (Long 1994).

Contributors

Sally Petrella (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

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.

World Map

altricial

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.

bilateral symmetry

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.

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

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.

fertilization

union of egg and spermatozoan

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

iteroparous

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).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

temperate

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).

territorial

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

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

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.