How to identify it
Typically three light stripes (one down the back, one on each side) on a black, brown, gray or olive ground; stripes may be white, yellow, blue, greenish or brown, sometimes absent or checkerboarded by dark spots. [1][2]
Head wider than neck and uniformly dark; red tongue tipped in black; keeled scales. [1][2]
19 dorsal scale rows at midbody, lateral stripe on rows 2 and 3, 7 upper labials, undivided anal scale. [1][2]
Adults usually 41-66 cm (to about 131 cm); some populations are entirely black; newborns 12-23 cm. [1][2]
Compared with the ribbon snakes (thamnophis sauritus, t. butleri): Close relatives of similar appearance; Animal Diversity Web lists them as the species commonly confused with the common gartersnake. [1][2]
Compared with the plains gartersnake (thamnophis radix): Plains gartersnake has its lateral stripe on scale rows 3 and 4 rather than 2 and 3. [1][2]
Compared with the terrestrial gartersnake (thamnophis elegans): Usually 8 upper labials and 21 scale rows at midbody, versus 7 and 19. [1][2]
Species it is confused with
Check these before deciding what you are looking at. If you are not certain what it is, do not shoot.
- Plains gartersnake · Thamnophis radix
- Terrestrial gartersnake · Thamnophis elegans
Where it lives
Very adaptable: meadows, marshes, woodland and hillsides, preferring moist grassy areas near ponds, lakes, ditches and streams, and common in suburbs with cover such as debris, boards or rocks. [1][2]
How it behaves
Active mainly by day across a wider range of temperatures than most snakes; hibernates from late October to March or early April, often communally in rodent or crayfish burrows, rock piles and stumps, and may bask on mild winter days. [1][2]
Limited legal take
Legal take of this species exists only under narrow conditions — a quota, a draw, a permit, a small area, or animals released or held on private land — set by the authorities below. Nowhere else is a legal opportunity implied, and Hunt shows one only where a certified rule establishes it.
Conservation and protection
- ENDANGERED — San Francisco garter snake (Thamnophis sirtalis tetrataenia): listed as endangered under the Endangered Species Act since 1967-03-11. · ECOS species profile: San Francisco garter snake
Where legal take is listed
- California — reptile take · 2026 California Freshwater Sport Fishing Regulations (updated July 10, 2026), 14 CCR 5.05/5.60
- Iowa — nuisance or unprotected take · 2026-27 Iowa Hunting, Trapping & Migratory Game Bird Regulations (DNR PDF; page numbers cited)
- Mississippi — reptile take · Title 40 Part 5 Rule 2.3 Regulations Regarding Non-Game Wildlife in Need of Management (MDWFP PDF; file dated 2024-04)
- Nevada — reptile take · CR 24-15 2025 & 2026 Seasons & Limits for Noncommercial Collection of Live, Unprotected Reptiles & Amphibians
- Pennsylvania — reptile take · 2026 Summary Book of Fishing Regulations, p.18 Reptiles and Amphibians
- Utah — reptile take · Reptile and amphibian species classification tables (R657-53), updated Apr. 22, 2026
Being listed is not an open season. Seasons, zones, licences, methods and limits decide whether this animal may be taken on a given day and place — check Hunt or the authority before you go. Listings read 2026-09-30.
Where it is found
Across much of North America from Florida to coastal Quebec and west to British Columbia, south into southern California east of the Sierras and through the less arid Southwest (largely absent from the arid southwestern United States).
Sources
Every claim above is attributed to one of these published sources.
NatureServe · reviewed 2026-09-30
NatureServe
University of Michigan Museum of Zoology · reviewed 2026-09-30
University of Michigan Museum of Zoology