General Description: The Lined Snake is a small fossorial snake, with adults ranging from 8–12 inches (20.3–30.5 cm) in length. The background coloration is gray, brown, or olive with three (one middorsal, two lateral) gray-white stripes running the length of the body. The belly is off-white with two rows of black half-moon shaped markings that run the length of the body (two marks per ventral scale). Juvenile coloration is similar to adult coloration. Scales are keeled and the anal scale is not divided. Lined Snakes are superficially similar to both the Common Gartersnake (Thamnophis sirtalis) and the Plains Gartersnake (Thamnophis radix) in appearance, but can easily be differentiated by the presence of the half-moon markings on the underside.
Behavior: Information on the behavioral ecology of this species is limited, especially at the northern extent of the range. The Lined Snake is active from April–October and may even be active into November provided warmer temperatures. Similar to most other snakes, Lined Snakes are solitary in behavior. Individuals can be found in close proximity while they are overwintering in den sites and when males seek out females during the reproductive season. Lined Snakes feed primarily on small invertebrates and earthworms. Like many snakes, this species will release a foul-smelling musk if captured.
Reproduction: Lined Snakes are ovoviviparous (gives birth to live young). Female Lined Snakes gave birth in mid-August, and the average clutch size is seven individuals (range: 2–12). The exact reproductive timing of Lined Snakes in South Dakota is currently unknown. Mating is thought to occur in the late fall after parturition (September, October) and again in the early spring after emergence from overwintering sites.
Habitat: Lined Snakes use many different habitats including prairie grasslands, scattered oak forests, and various residential and suburban areas; however, most literature suggests this species inhabits remnant, undisturbed prairies along woodland corridors.
Species Range: This species has a distribution across much of the Great Plains and the Rocky Mountains. Populations span from southern Texas and reach their northern limit in southeastern South Dakota and the southwest corner of Minnesota, and isolated populations exist in Wisconsin, Iowa, Illinois, Colorado, and New Mexico.
South Dakota Range: Lined Snakes have a limited distribution in South Dakota and are found along the Big Sioux River corridor north to Palisades State Park in Minnehaha County. Recently, a population of Lined Snakes was in Hutchinson County, suggesting this species may also occur along the James River corridor.
South Dakota Status: This species is listed as endangered by South Dakota Game, Fish and Parks. Any sightings of this species should be reported to South Dakota Game, Fish and Parks (report observation).