Discover the 3 Water Snakes Lurking in Washington State Waters

Written by Hannah Ward
Updated: June 14, 2023
© K Quinn Ferris/
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The state of Washington has numerous aquatic habitats in it, from its Pacific coastline to the vast Snake River. Therefore, although the state is home to approximately 21 species of snakes, you might be surprised to find that there are no true water snakes in Washington. However, there are still three semi-aquatic snakes that can be found in and around its wetlands. Let’s find out which they are!


Now read on for more detailed information about these three Washington snakes!

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1. Common Garter Snake (Thamnophis sirtalis)

A common garter snake slithering in grass
Common garter snakes rely heavily on the water for food, preying mostly on fish and amphibians.


The common garter snake is the first of the three semi-aquatic snakes in the state. Common garter snakes are one of the most common snakes in Washington and occur statewide. They almost always live in areas close to water, with habitats including swamps, streams, ponds, and rivers. They are excellent swimmers and rely heavily on the water for food, preying on a variety of amphibians and fish. Common garter snakes are ambush predators and seize their prey before swallowing it alive. However, they often slow their prey down through the use of a venom-like substance which is produced in the Durvenoy’s gland. This substance isn’t true venom and isn’t dangerous to humans. It is chewed into their prey instead of being injected.

Common garter snakes can be anything from 18 to 30 inches long and have an appearance that can vary widely. However, they almost all share the same basic identifying features of a dark brown to gray ground color and three lighter-colored stripes. The dorsal stripe is situated down the center of their back, while they also have a lateral stripe on the second and third row of scales on each side of their body. Their stripes are usually yellow or orange, but may be blue or green in some areas. They also often have red or black blotches between their stripes.

Common garter snakes are typically active between March and November. Mating occurs in the spring, and during this period it is not unusual to see large “mating balls”. These balls consist of several males wrapped around a single female in an attempt to mate with her. The females give birth in the late summer or early fall and the juveniles are approximately seven inches long.

2. Western Terrestrial Garter Snake (Thamnophis elegans)

Western terrestrial garter snakes typically live close to water.
Western terrestrial garter snakes can immobilize their prey using a venom-like substance in their saliva.

©Randy Bjorklund/

The next water snake in Washington state is the western terrestrial garter snake. Western terrestrial garter snakes are 18 to 41 inches long and have gray to brown bodies with three thin yellow or cream stripes. Again, the lateral stripes occur on the second and third rows of scales. Western terrestrial garter snakes also have a number of black (and sometimes red) spots which are in alternate rows between the lateral stripe and the one down the center of their back.

Western terrestrial garter snakes are fairly widespread across Washington and predominantly live close to water — in areas such as ponds, stream edges, lakes, rivers, and swamps. Despite this, these snakes typically overwinter on rocky talus slopes and hillsides. Western terrestrial garter snakes have a varied diet but prey heavily on fish and frogs. Like the common garter snake, they immobilize their prey using their toxic saliva. However, again, they pose no threat to humans.

Western terrestrial garter snakes are active from early spring to late fall. In the Puget Sound region pregnant females of all three garter snake species can be found congregating in the same area. These snakes are ovoviviparous so they give birth to live young once their eggs have hatched inside them. This typically occurs in the late summer and early fall, with litters consisting of between eight and 12 snakes.

3. Northwestern Garter Snake (Thamnophis ordinoides)

Northwestern garter snakes can have red, yellow, blue, green, orange, or cream stripes.
Northwestern garter snakes are the smallest species of garter snake in Washington state.


The final snake is the northwestern garter snake which is common across only the western half of Washington state. These snakes are frequently found near water but are not usually associated with open water, preferring areas such as stream edges instead. Northwestern garter snakes prey on a variety of frogs, salamanders, and slugs. They are not venomous and are not dangerous to humans. However, they may sometimes defecate or release a musk-scent if they are threatened.

Northwestern garter snakes are the smallest species of garter snake in Washington and are rarely longer than 23 inches. They are typically have either a black or brown ground color, but the color of their stripes can vary widely. They can be either blue, green, yellow, orange, red, or white. Northwestern garter snakes also often have several small, dark spots between their lateral stripes.

These snakes mate in the early spring, between March and April, when they emerge from the dens that they have overwintered in. The neonates are born in the summer and early fall, although in the lower Puget Sound area they are typically born between late August and early September.

Summary of 3 Washington Water Snakes:

None of these snakes pose a danger to humans. The Northwestern Garter is non-venomous. The Western Terrestrial Garter has a toxic venom it uses to immobilize its prey. The Common Garter has a glandular secretion it chews into its prey to slow it down. The table shows other differences and commonalities:

Name of SnakeLength in InchesFoodHabitat
Common Garter18-30Amphibians and fishSwamps, streams, ponds, rivers
Western Terrestrial Garter18-41Frogs and fishSwamps, stream edges, ponds, rivers, lakes
Northwestern Garterup to 23Frogs, salamanders, slugsStream edges, but not open waters

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Garter snakes are harmless to people, but have mildly venomous saliva.
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About the Author

I have been writing professionally for several years with a focus on animals and wildlife. I love spending time in the outdoors and when not writing I can be found on the farm surrounded by horses, dogs, sheep, and pigs.

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