‹ Compare two snakes
Checkered Gartersnake vs Common Gartersnake
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(c) Jason Layman, some rights reserved (CC BY-SA)
Checkered Gartersnake
Thamnophis marcianus
Non-venomousMatt Kenne, no rights reserved
Common Gartersnake
Thamnophis sirtalis
Mildly venomousThe quick way to tell
Look at where the pale side stripe sits near the head. The Checkered Gartersnake's side stripe is on the third row of scales up from the belly, with bold black checkerboard squares above it. The Common Gartersnake's side stripe is lower, on the second and third rows.
Pattern ★ This settles it
Thin yellow, cream or orange stripe down the middle of the back, and a pale stripe low on each side (near the head it sits on the third row of scales up from the belly). Between the stripes are black squarish spots in an alternating checkerboard. The belly is cream to light gray with few or no markings. The scales are keeled.
Three pale stripes - spine and low on each side - often with red flecks between.
Head
A cream or yellow crescent at the back of each side of the head, with a dark blotch on the neck just behind it. The lips have light and dark vertical bars, and there is a small light spot on top of the head.
Small head barely wider than the neck; often with pale jaw markings.
Eyes
Round pupils.
Round pupil, fairly large dark eye; no heat-sensing pit.
Pits
None. There is no pit between the eye and the nostril.
None. There is no pit between the eye and the nostril.
Tail
—
Fairly short, about a quarter of its length; no rattle.
What it does
May bite when first caught and may smear musk and droppings on the handler. Good at finding new water sources such as isolated cattle tanks. Groups may spend winter together.
Flees for cover; musks and may give a scratchy bite if held.
Where it lives
Southwestern and south-central US (southeastern California, Arizona, New Mexico, Texas, Oklahoma, southern Kansas) south through Mexico to Central America (Costa Rica).
Nearly all of the United States and southern Canada, except the driest Southwest.