Name: Common Gartersnake (Thamnophis sirtalis)
Order: Snakes (Squamata)
Family: Common Snakes (Colubridae)
What they look like
- Common Gartersnake coloration varies based on locality, with up to 13 subspecies described based appearance across their North American distribution. In Washington, two subspecies can be found.
- The Puget Sound Gartersnake (Thamnophis sirtalis pickeringii, pictured), which is slender and black with turquoise or black bellies and bright yellow or turquoise dorsal and lateral stripes and occasional vertical red flecks on their sides;
- The Valley Gartersnake (Thamnophis sirtalis fitchi), which often has more pronounced red blotches in on the sides, thicker yellow dorsal and lateral stripes, and often red bellies. Research is ongoing to determine if these color pattern differences between populations across North America are local adaptations or indicative of shared evolutionary history.
Where they live
- Common Gartersnakes have the greatest distribution of any Gartersnake, with a range extending as far North as northern Alberta Canada and throughout the United States to the exclusion of the desert Southwest.
- In the Pacific Northwest, they can be found near water—marshes, ponds, streams, and other moderately moist habitats with tall grasses.
Average litter size varies considerably across the Common Gartersnake’s range, with most gravid females birthing between 10 and 15 snakes. However, in some populations the average litter size can be as high as 32 and exceptionally large females have been recorded giving birth to up to 85 offspring.
Cool biology facts
The Common Gartersnake is the only animal known to be capable of harboring resistance to tetrodotoxin (TTX), a potent neurotoxin produced by the rough skinned newt and Japanese pufferfish. Frequency of TTX resistance in Common Gartersnake populations is often proportional to the toxicity levels of rough skinned newt populations in the same area.