Tropidoclonion lineatum (Hallowell, 1856)
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Basis for Listing
The lined snake occurs within the Great Plains states, extending from southeastern South Dakota to Texas. Disjunct populations occur in New Mexico, Colorado, and Illinois. Despite this wide range, the species has only been recorded in Minnesota at Blue Mounds State Park in Rock County. It was first reported in Minnesota in 1980, although an earlier reference (Wright and Wright 1957) lists it as ranging into southwestern Minnesota. Due to its limited distribution in the state, the lined snake was listed as a special concern species in Minnesota in 1984.
The lined snake is a small, slender snake. Adults range from 22-38 cm (8.7-15 in.) long, with the record size being 54.4 cm (21.4 in.) long (Conant and Collins 1998). The young are 7-13 cm (2.8-5 in.) long (Ernst and Barbour 1989; Oldfield and Moriarty 1994). The dorsal (back) color is grayish to brownish, and there is a stripe down the back that varies from whitish to orange. There are 2 additional stripes down the sides on the second and third dorsal scale rows (Oldfield and Moriarty 1994; Conant and Collins 1998). The ventral (belly) scales are light-colored with a double row of black half-moons. The scales are keeled and the anal plate is single (Oldfield and Moriarty 1994; Conant and Collins 1998). Gartersnakes (Thamnophis spp.) in Minnesota may resemble the lined snake, but they lack the double row of black half-moons on their belly (Oldfield and Moriarty 1994).
The lined snake is typically found in grassland and open woodland habitats, but it has been found in urban areas in some part of its range. In Minnesota, its habitat consists of rock outcrops in rolling prairie in Blue Mounds State Park. The lined snake is secretive, hiding under rocks, logs, boards, leaves, or other surface debris.
Biology / Life History
The lined snake is believed to overwinter in rock crevices and animal burrows located beneath the frost line, and emerge from hibernation in late April (Oldfield and Moriarty 1994). This species is primarily nocturnal, but may bask during the day in the spring and early fall (Ernst and Barbour 1989; Oldfield and Moriarty 1994). Females mature in 2 years, and may give birth yearly (Oldfield and Moriarty 1994). Breeding generally takes place in the fall, but fertilization is delayed until the spring (Ernst and Barbour 1989; Oldfield and Moriarty 1994). In August, 2-13 young are born alive in thin transparent membranes from which they emerge (Oldfield and Moriarty 1994). Hatchlings range from 7-13 cm (2.8-5 in.) in length (Ernst and Barbour 1989; Oldfield and Moriarty 1994). Lined snakes feed primarily on earthworms, but they have also been recorded eating sowbugs (Ernst and Barbour 1989; Oldfield and Moriarty 1994). They forage at night or during a rainstorm when earthworms are active. Lined snakes are preyed upon by carnivorous mammals and a variety of birds (Ernst and Barbour 1989).
Conservation / Management
Although the lined snake is somewhat tolerant of disturbed habitats, it is highly susceptible to mortality on busy roads. Additionally, the preferred habitat of the species is vulnerable to agricultural cultivation, grazing, and residential and commercial development. Lined snakes are declining in Iowa with the loss of woodland and edge habitats, and in 2004, Illinois afforded the species threatened status due to urbanization and loss of habitat.
Conservation Efforts in Minnesota
In Minnesota, Blue Mounds State Park is the only site where lined snakes have been documented, although surveys have been conducted elsewhere. Lined snakes are occasionally observed in the park but the status of this population is unknown. In 1984, a survey conducted by the Minnesota Herpetological Society in the Missouri River drainage documented one road-killed specimen within Blue Mounds State Park, but searches outside the park were unsuccessful at locating additional records (Moriarty 1984). The Minnesota Biological Survey targeted this species during surveys of southwestern Minnesota in 2006. Two adult snakes and one juvenile were captured among scattered rock outcrops in grasslands at Blue Mounds State Park. In addition, four lined snakes (three dead; one alive) were found on roads within and adjacent to the park. No lined snakes were located in searches outside the park during this survey. Further survey efforts are needed to locate additional populations of this species in southwestern Minnesota. Conservation measures that connect protected patches of habitat across the landscape would enhance the viability of Minnesota's only known lined snake population.
Conant, R., and J. T. Collins. 1998. A field guide to reptiles and amphibians of eastern and central North America. Third edition. Houghton Mifflin Company, New York, New York. 616 pp.
Ernst, C. H., and R. W. Barbour. 1989. Snakes of eastern North America. George Mason University Press, Fairfax, Virginia. 282 pp.
Moriarty, J. J. 1984. Amphibians and reptiles of the Missouri River drainage of southwestern Minnesota. Final report submitted to the Minnesota Department of Natural Resources. 19 pp.
Oldfield, B., and J. J. Moriarty. 1994. Amphibians and reptiles native to Minnesota. University of Minnesota Press, Minneapolis, Minnesota. 237 pp.
Wright, A. H., and A. A. Wright. 1957. Handbook of snakes of the United States and Canada. 2 Volumes. Comstock Publishing Associates, Ithaca, New York. 1105 pp.