Aquatic Garter Snake
Thamnophis atratus
A strongly aquatic garter snake of Pacific coast streams and rivers, closely tied to clean flowing water.
- Venomous?
- Mildly venomous
- Adult length
- 0.5-1.0 m (1.6-3.3 ft)
- Range
- Pacific coast from southwestern Oregon through California
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Overview
The aquatic garter snake is a water-dependent species found along the Pacific coast from Oregon south through California, often in fast-flowing, rocky streams.
Several subspecies vary in coloration, with some populations showing striking orange or yellow dorsal stripes against dark bodies.
How to identify it
- Dark olive, gray, or black background
- Dorsal stripe may be yellow, orange, or reduced depending on subspecies
- Faint or absent lateral stripes in some populations
- Keeled scales
- Round pupils
- Distinguished by strong association with rocky streams and reduced lateral striping compared to other garter snakes
Habitat & range
Found along rocky, clear streams, rivers, and lake margins in forested and coastal habitats from southwestern Oregon through much of California, including coastal ranges and the Sierra Nevada foothills.
Behavior, diet & reproduction
Highly aquatic, frequently seen basking on rocks near water and diving in when disturbed. Feeds on fish, tadpoles, and frogs, hunting both underwater and along stream banks. Gives birth to live young in summer.
Frequently asked questions
Is the aquatic garter snake venomous?
It has mildly toxic saliva for subduing small prey but is not dangerous to humans.
Where does it live?
It occurs along clean, rocky streams and rivers from southwestern Oregon through California.
How can it be recognized?
Look for a dark body with a variably colored dorsal stripe and strong ties to flowing water habitats.
What does it eat?
It preys mainly on fish and amphibians found in and near streams.
Aquatic Garter Snake guides
In-depth guides for identifying and understanding Aquatic Garter Snake.
