|Common Name:||Eastern Gartersnake|
|Scientific Name:||Thamnophis sirtalis sirtalis|
|Genus:||Thamnophis is derived from the Greek words thamnos which means "bush" and ophio meaning "snake".|
|Species:||sirtalis is Latin and means "like a garter".|
|Subspecies:||sirtalis is Latin and means "like a garter".|
|Vernacular Names:||Adder, blue spotted snake, broad garter snake, brown snake, Churchhill's garter snake, common streaked snake, common striped snake, dusky garter snake, first and last garden snake, grass garter snake, green spotted garter snake, hooped snake.|
|Average Length:||18 - 26 in. (45.7 - 66 cm)|
|Virginia Record Length:||43.3 in. (110 cm)|
|Record length:||48.7 in. (123.8 cm)|
Common Ribbonsnake vs. Eastern Gartersnake
PHYSICAL DESCRIPTION: This species is from 5-48 inches long *1101*. It is the only garter snake throughout most of its range with ateral stripes confined to rows 2 and 3. Either stripes or spots may predominate. There are normally 3 yellowish stripes, but they may be brownish, greenish, or bluish. There is usualy a double row of alternating back spots between stripes. The spots are sometimes prominent and invading the stripes. Occasionally, specimens are virtualy stripeless. The belly is greenish or yellowish, with 2 rows of indistinct back spots partialy hidden under the overlapping portions of the ventrals. The scales are keeled *882*. At elevations above 1,067 feet in the Great Smoky Mountain Natinal Park, melanistic individuals have been reported *11502,11523*. In Thorp's observations, specimens in the mountains tend to have a darker body color than in the piedmont or coastal plain *11523*. In Va., max known SVL is 898 mm (35.6 in.) and maximum total lenth is 100 mm (43.3 in.) *10760*. Outside Virginia, the maximum known total length is 48.75 inches *11523*. Adults are usually 18-26 inches in length *11523*. Tail length/total length ratio is 15.4-27.9% (avg. = 22.0+/-2.2, n=151). Scutellation: ventrals 128-155 (avg. = 142.8+.-4.4, n=211); subcaudals 52-81 (avg. = 66.5+/-6.7, n=151); ventrals + subcaudals 189-232 (avg. = 209.5+/-9.8, n=164); dorsal scales keeled; scale rows 19 at midbody; anal plate single; infralabials 10-10 (68.9, n=177), other combinations of 8-11 (31.1%); supralabials 7-7 (78.9%, n=185), other combinations of 6-8 (21.1%); loreal scale present; preoculars 1-1; postoculars 3-3; temporal scales usually 1+2/1+2 (48.6%, n=177) or 1+3/1+3 (24.9%), other combinations of 1-4 (26.5%).
COLORATION and PATTERN: dorsum of body and tail greenish, olive, brown, or black with a distinct yellow or white middorsal stripe: dorsum may have a pattern of alternating, squarish, black and green spots in a checkerboard pattern between the stripes or be almost uniformly dark; in some individuals the upper and/or lower edges of the body scales are white; a lateral white to yellow stripe on scale rows 2 and 3 may be present, although it is less distinct than the middorsal stripe, or mayt be absent in some individuals; color of the first scale row and the lateral margins of the ventral scales is not as dark as those above scale row 3, color varies from yellowish-green to gray; venter cream to yellowish-green and patternless except for one to several small black spots near the lateral margins of each ventral scale; dorsum of head greenish, brown, or nearly black; tip of snout brown; in some individuals 2 black blotches project obliquely from the parietal scales and are bisected by the middorsal stripe; supralabial scales cream-colored and are entirely or partially edged in black; chin and infralabials white. *10760*
SEXUAL DIMORPHISM: Females reach a larger average SVL (515.3+/-105.0 mm, 395-898, n=102) than males (408.7-56.4 mm, 338-585, n=53), and reach a greater max total length (1100 mm, males 727 mm). Sexual dimorphism index is 1.26. The tail length/total length ratio is slightly higher males (18.3-27.9%, avg. = 23.6+/-1.8, n=60) than females (15.4-26.2 %, avg. = 20.9+/-1.7, n=91). Males have higher average numbers of ventral scales (145.5+/-4.2, 137-155, n=73) and subcaudal scales (71.7+/-5.6, 55-81, n=62) than females (ventrals 141.4+/-3.9, 128-154, n=138; subcaudals 63.3+/-5.2, 52-79, n=102). The number of ventrals + subcaudals averages higher in males (217.4+/-7.7, 194-232, n=62) than in females (204.7+/-7.6, 189-232, n=102). Wood & Wilkinson found that relative tail length and number of subcaudal scales in a litter of neonate T. sirtalis from Newport News was distinctly higher in males. Shine and Crews demonstrated that females had significantly longer heads than males for the same body size in museum samples from Va. and other locations.*10760*
JUVENILES: Juveniles are pattered as adults, but are brown dorsally with cream venters and usually exhibit the checkerboard pattern of squarish black or dark brown and green blotches. The dorsal pattern darkens with age. Neonates are 115-150 mm SVL (avg. = 131.2+/-7.5, n=100), 150-200 mm total length (avg. = 169.6+/-9.9, n=100) and weigh 1.0-2.1 g (avg. = 1.7+/-0.2, n=45).*10760* Confusing Species: This species may be confused with the ribbon snake, Thamnophis sauritus, which has distinct, lateral, yellow stripes on scale rows 3 and 4, is much more slender, and has a longer tail (>27% of total length).*10760*
GEOGRAPHIC VARIATION: Thamnophis sirtalis populations in the lower Coastal Plain have the lowest average counts of ventrals and subcaudals, whereas those in the Cumberland Plateau region the highest. Accordingly, ventrals vary from 139.4+/-3.9 (132-152, n=19), to 146.7+/-4.7 (141-155, n=9), subcaudals from 64.0+/-7.5 (55-77, n=11) to 71.6+/-7.8 (58-81, n=7), and ventrals + subcaudals from 203.9+/-10.4 (189-225, n=11) to 217.6+/-11.1 (200-229, n=7). Counts for other Va. populations fall within these values. Upper elevation populations (>3000 feet) of this species usually lack lateral stripes, and the middorsal stripe is reduced to a thin line or is faded. The dorsum of these snakes is often darker than those at low elevations.*10760*
REPRODUCTION: This snake will mate on the 1st warm day after their emergence in spring. The young are born alive in late July or early August *1008,1101*. They have 7-101 young/litter *1104*, which are 5-9 inches long at birth *882*. A single female may be courted by many males at the same time, forming a "mating ball". The estimated age at maturity for females in Kansas is 2 years. Mitchell reports litter size to be between 9-57 (avg. = 26.2+/-16.8, n=22).*10760*
BEHAVIOR: This species is diurnal, becoming nocturnal in hot weather *2065*. It hibernates in November *2068,1008*, through March *2068*, in rocky outcrops with deep crevices or rotting stumps *2068*. The activity range is 2-3 acres, estimated. 482 garter snakes are estimated to inhabit a 48-acre study area *2070*. This species has a preference for damp habitat *2064,1008,883*, although it occurs in a wide variety of habitats *883,2064,1013* including the edges of waterways *882,1101*, meadows, marshes, woodlands, hillsides *882*, weedy or brushy areas and old fields *1013*. They are also in waste places in cities *1013*, and in city lots and dumps where there is moisture, or at least dampness *882*. A Kansas population experienced 36% first-year survival rate, a 50% adult annual survival rate, and an estimated natural longevity of 8 years.*10760* Thamnophis sirtalis will often flatten its head and anterior body and strike if molested. Juveniles especially will perform this behavior and will strike so forcefully that they may completely leave the ground. Adults will also spray musk from glands located at the base of the tail, and sometimes emit feces in attempts to discourage predators.*10760* Thorp has found this species in its natural habitats as well as on roads and under coverboards *11523*.
ORIGIN: This species is native *883,2064*.
POPULATION PARAMETERS: The longevity record for this species is 6 years and 7 months *11523*.
AQUATIC/TERRESTRIAL ASSOCIATIONS: This species is associated with Lumbricus sp., Anaxyrus americanus, Lithobates sp., Thamnophis sauritus sauritus, Storeria dekayi dekayi, Notophalmus viridenscens, Quercus sp., Pinus sp., Dactylis glomerata, Setaria sp. and Crataegus sp. *883,2064*.
References for Life History
*Click on a thumbnail for a larger version.
|Chesapeake||Fairfax Co.||Fairfax Co.||Loundoun Co.|
|Erythristic specimen from Chesapeake||Lynchburg||Prince William Co.||Prince William Co|