(Thamnophis sirtalis)

Description

Ranges from 18 – 30 inches in size, with females being larger. Coloration varies widely, but is usually ranges from brown to almost black with a light colored dorsal stripe and lateral stripes on the second and third scale rows up from the belly scale. The Texas Gartersnake usually has a broad, orange mid-dorsal stripe, however hues can vary in tone from reddish to nearly yellow. Furthermore, it has a lateral stripe on scale rows 2, 3, and 4. The red-sided subspecies usually has a cream-colored dorsal stripe (or more orange within intergrade zones with annectens) and has bright red or orange coloration between its scales. The Eastern subspecies usually has a narrow, yellowish mid-dorsal stripe and an overall yellowish hue on the sides.

Distribution

The Common Gartersnake is widespread throughout Eastern, Central, and northwest Oklahoma. It is absent from most of southwest Oklahoma as well as the western portion of the panhandle.

Habitat

A habitat generalist in many respects as long as a water source is nearby. It can be found in habitats ranging from open woodlands, prairies, and bottomland hardwood forests to abandoned lots and urban waterways. Individuals can adapt to a fair amount of urban development and are occasionally found around human dwellings.

Diet

Feeds primarily on amphibians, earthworms, and small fish, but will occasionally prey on small reptiles and rodents.

Reproduction

Common Gartersnakes are ovoviviparous. They mate shortly after emerging from hibernation in early spring and females will give birth to live young in early to mid-summer. Litter sizes can range from 5 to over 30.

Similar Species

The Orange-striped Ribbonsnake is found almost statewide and occurs in similar habitats as T. sirtalis. However, the lateral white lines are higher up on the sides and the labial scales are all-white. Furthermore, ribbonsnakes are typically more slender and less bulk overall. The Plains Gartersnake (T. radix) is overlapping in range in northwestern Oklahoma and can strongly resemble the Texas subspecies of T. sirtalis (annectens) but is typically found in more open and dryer sites. It also tends to have a lighter base color than most specimens of T. sirtalis and often has a checkerboard pattern.

Remarks

Oklahoma has three subspecies of T. sirtalis, all three of which are relatively poorly delineated in distribution and require further study; these include the red-sided gartersnake (T. s. parietalis), Texas Gartersnake (T. s. annectens), and Eastern Gartersnake (T. s. sirtalis). As noted by Lardie (Lardie 2001) and more recently in Powell et al. 2016, T. s. parietalis is mapped as occurring throughout the central part of the state and ranging all the way south to the Red River, with T. s. annectens having a disjunct distribution in Northwest Oklahoma and T. s. sirtalis only occurring in a very narrow strip along the eastern edge of Oklahoma from the Ozark Highlands to the Ouachita Mountains and Gulf Coastal Plain. However, snakes that appear to be phenotypic T. s. annectens occur consistently throughout south-central Oklahoma, where they meet with T. s. parietalis in central Oklahoma. T. sirtalis in central Oklahoma counties (notably Logan, Oklahoma, Cleveland, and McClain) vary in appearance and can display characteristics of both annectens and parietalis. In addition to northwestern Oklahoma, T. s. annectens may also range further into east-central portions of the state, as snakes in south Tulsa Co. resembling the phenotype have been reported. T. sirtalis in LeFlore and McCurtain counties are thought to be annectens x sirtalis intergrades; however, more research needs to be done on snakes within this portion of the state. The Texas and Red-sided subspecies most likely meet and interbreed throughout much of central Oklahoma, probably in a “U”-shape ranging from Woods Co., going south to Logan Co., and to the northeast reaching Tulsa Co.

Sources

Lardie, R. 2001. The Subspecific Status of the Common Gartersnake, Thamnophis sirtalis, in Western Oklahoma. Kansas Herpetological Society Newsletter No. 123 (March 2001). Powell, R., Conant, R. & J. T. Collins. 2016. Peterson Field Guide to Reptiles and Amphibians of Eastern and Central North America. Houghton Mifflin Harcourt Publishing. Sievert, G. and L. Sievert. 2011. In L. B. Carson and M. D. Howery (Eds.). A Field Guide to Oklahoma’s Amphibians and Reptiles (pp. 192-193).