Common Garter Snake (Thamnopis sirtalis)

A close up picture of a garter snake
Common Garter Snakes are slender and stealthy, blending in with grass to ambush prey.

NPS Photo

Common Garter Snake
Thamnopis sirtalis

  • The common garter snake is a slender, medium-sized snake.
  • Adults range from 18-30 inches in total length.
  • Typically, active from March to November. This is an active snake, but during the summer may shift activity to become more nocturnal to avoid the heat.
  • Individuals have a tan or pale yellow middorsal stripe extending down the entire length of their body.
  • The secondary coloration is typically tan, and an additional lateral stripe exists on each side of the body that occurs on scale rows two and three.

  • Their diet consists mostly of amphibians, earthworms, or other soft-bodied invertebrates.
  • These snakes will also eat other snakes when available.

Interaction with other animals
  • Predators include coyotes, foxes, other snakes, and most birds of prey.
  • When threatened, they often flatten and extend their bodies, showing the red color on their scales.
  • Upon capture, they will release a foul-smelling musk.

Last updated: January 9, 2024

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Contact Info

Mailing Address:

11149 U.S. Hwy. 16
Building B12

Custer, SD 57730


605 673-8300
The main phone line connects visitors with staff at the visitor center. Throughout the year, the phone line is monitored by staff on a daily basis, excluding holidays and days with limited visitor services. Please be advised that after-hours messages are not taken on the system; visitors are encouraged to call the visitor center during normal operations and speak with a park ranger for assistance.

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