How to identify it
Checkered pattern of black and light-gray spots along the body, with pale-yellow stripes on the spine and sides and a cream belly. [1][2]
Olive-green head with a single thick black line on the neck and a pale-yellow crescent just behind the head; red tongue with a black tip. [1][2]
21 rows of keeled dorsal scales; adults 45-106 cm, average about 55 cm; females bulkier and longer than males. [1][2]
Juveniles show the same checkerboard as adults. [1][2]
Compared with the black-necked gartersnake (thamnophis cyrtopsis): Black-necked has 19 dorsal scale rows and two black blotches on the neck sides, versus 21 rows and a single black neck line in the checkered. [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.
- Black-necked gartersnake · Thamnophis cyrtopsis
Where it lives
Sea level to about 2,200 m, from wetlands to drylands, always at or near water (rivers, ponds, springs, irrigation ditches, lakes); also backyards and gardens, and it is spreading west along irrigation canals. [1][2]
How it behaves
Mainly diurnal, but active at night in southern habitats; solitary, hibernating in groups of around 100 from October to March and basking on warm winter days. [1][2]
Hunts small prey in irrigation ditches and streams using smell and sight; eats earthworms, tadpoles, frogs, salamanders, fish, lizards, mice, slugs and eggs (juveniles favour earthworms, adults tadpoles). [1][2]
Uses species-specific pheromone trails to find mates; males follow females more than females follow males. [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.
Where legal take is listed
- California — reptile take · 2026 California Freshwater Sport Fishing Regulations (updated July 10, 2026), 14 CCR 5.05/5.60
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
Southwestern California, southwestern Arizona and southern New Mexico in the United States (abundant along the Gila and Colorado rivers), plus Mexico and Central America per Animal Diversity Web. Not in Canada.
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