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.

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: South-central Canada to Texas and from Montana, Wyoming, Utah, and eastern Arizona to Michigan, Ohio, Missouri, and Oklahoma.

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)

Range mass: 110.0 to 140.0 g.

Range length: 170.0 to 310.0 mm.

Average length: 250.0 mm.

Sexual Dimorphism: sexes alike

Average basal metabolic rate: 0.983 W.

Length: 30 cm

Weight: 270 grams

• Terrestrial

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)

Habitat Regions: temperate

Comments: Restricted to dry and sandy (and "tighter") soils of open areas, such as grasslands, cultivated fields, meadows, roadsides, airfields, shrublands, and suburb lawns. Beaches and dry pine barrens also used. Rests, gives birth, and hibernates in underground burrow.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

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

Foraging Behavior: stores or caches food

Primary Diet: omnivore

Comments: Diet consists of plant and animal foods: seeds, fruits, grasses, forbs, as well as insects. May sometimes eat small vertebrates.

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.

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:

• birds of prey (Falconiformes)
• snakes (Serpentes)

Although not colonial, does prefer to live in loosely constituted families. Home ranges range from less than an acre to 12 acres; male range larger than that of female (Gunderson 1976). Densities vary from 1-20 per acre (Schwartz and Schwartz 1981)

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.

Comments: Enters hibernation by October (adults may hibernate beginning in July), emerges in March or early April.

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.

Spermophilus tridecemlineatus is promiscuous. Females mate within five days of spring emergence from hibernation. Copulation stimulates ovulation within 1 to 2 days. Gestation lasts 28 days. Between 7 and 14 young are born, with an average of 8 to 9. They are blind, hairless and toothless and weigh 4 gm. The young gain 1.3 gm/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, offspring dig their own burrow, usually within 100 m of where they were born. Females have one annual litter. Up to 90% of newborns die from predation before hibernation begins. (Kurta 1995, Jones 1988, Palmer 1995)

Breeding interval: Each year females only give birth to one litter.

Breeding season: Upon emergence from hibernation, April or early May

Range number of offspring: 6.0 to 13.0.

Average number of offspring: 8.5.

Average gestation period: 28.0 days.

Average weaning age: 6.0 weeks.

Average age at sexual or reproductive maturity (female): 1.0 years.

Average age at sexual or reproductive maturity (male): 1.0 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Average birth mass: 3.24 g.

Average gestation period: 28 days.

Average number of offspring: 7.

Average age at sexual or reproductive maturity (male)

Sex: male: 225 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 354 days.

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.

Parental Investment: altricial

Breeding period is April-June. Gestation lasts 27-28 days. Litter size averages 8 (13 maximum), perhaps larger in older females than in younger ones; 1 litter per year. Young are weaned in 26 days, emerge from burrow about 5 weeks after birth. Sexually mature by first spring.

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

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

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

Comments: Known to hybridize at several localities with S. mexicanus (see Thorington and Hoffmann, in Wilson and Reeder 2005).