The Southern Durango spotted garter snake (Thamnophis nigronuchalis) is a species of snake of the family Colubridae. It is endemic to the state of Durango, Mexico.
This is a heavy-bodied, medium sized garter snake. It has an oval-shaped head with two supralabial scales, two preocular scales, and a distinct black blotch on the dorsal surface of its neck. It has 149-165 ventral and 63-70 caudal scales. Ventral scales are heavily pigmented, often forming an irregular black stripe. The dorsal pattern consists of rufous-colored spots outlined in black in 5-10 rows, with no dorsal or lateral stripes.[1]
While it is now considered a valid species,[2] some authorities have classified this snake as a subspecies of the narrow-headed garter snake under the name Thamnophis rufipunctatus nigronuchalis.[3]
The specific name nigronuchalis references the Latin word nigro meaning black, and nuchal meaning of the nape, and is derived from the black neck patch characteristic of the species.[1]
This snake is endemic to Durango state in Mexico,[4] where it is found in wet meadows and riparian areas at altitudes of 8500–9000 feet.[1] It appears to be restricted to high elevation drainage basins of the Sierra Madre Occidental.[5]
This species has been documented to eat earthworms and amphibians, including Rana pipiens and Hyla species.[1]