Garter Snake Identification Key

The garter snakes found in Washington can be locally common as these range maps demonstrate for the Common, Northwestern, and Western garter snakes.

With a little practice, identifying the three different species can be as easy as counting scales.

By looking more closely at the head and specifically the row of scales along the upper lip (called labial scales), you can narrow down the species of garter snake.

photo: RAN

If the snake has 7 upper labials (as shown in the picture), you have either a Northwest garter snake or a Common garter snake.

If you count 8 upper labials it is a Western garter snake.

Now to distinquish between the Northwest garter snake and the Common garter snake, you have to turn the snake over. and count the scales along the belly.

photo: RAN

Count across diagonally or in a 'V' pattern. You'll get the same number.

17 belly scales = Northwest garter snake
19 belly scales = Common garter snake

...There are always some individuals who will be an exception to the rule. If you find one, record the snake's color and markings.

Photo acknowledgments: RAN=R. A. Nussbaum et. al., Amphibians and Reptiles of the Pacific Northwest, University of Idaho Press, Moscow, Idaho 1983