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The Valley Gartersnake is a subspecies of the Common Gartersnake and is distributed from Canada through Washington, Idaho, and Oregon into northern California and Utah. It is found in extreme western Wyoming, in the foothills and lower montane life zones from Yellowstone NP south into the drainages of the Snake River and Bear River. It is rarely found far from permanent water where it resides in the riparian habitat along streams and floodplains and the margins around ponds and marshy areas.
They are diurnal snakes and active from April through September, feeding on small fish, frogs, mice, and invertebrates such as earthworms, slugs, and leeches. When alarmed or frightened, they have been reported to “stand their ground” by coiling in a defensive posture and striking. When handled they will attempt to bite and smear a cloacal discharge before becoming docile.
These are medium sized snakes with a total length (TL) in the range of 24-30 inches; females are much larger than males. Their scales are keeled and the anal plate is entire. The dorsal background is a dark gray or brown to almost black with three longitudinal stripes running along the body. The midline stripe is a cream to dull yellow and the lateral stripes, located on the 2nd and 3rd row of scales up from the belly, are paler and less distinct. The area between the dorsal and lateral stripes has a black and red checkerboard pattern. The belly is white or cream to bluish-gray and is generally without black spots or blemishes.
In Wyoming they are identified as garter snakes by the three longitudinal stripes. They are distinguished from the Plains Gartersnake by the absence of black margins on the labial scales of the upper jaw. They differ from the Wandering Gartersnake by the presence of the red and black checkerboard pattern between the dorsal and lateral stripes.
Some descriptions in the literature distinguish this subspecies from the Red-sided Gartersnake subspecies by the lack of black spotting on the margins of the belly plates and by having a darker background on the body and head. However, in Wyoming there is considerable blending of these traits between these two subspecies of Common Gartersnake. The presence or absence of black spots on the anterior margins of the ventral scales varies along the length of the body of individual snakes, and the density or amount of black on the head and the background of the body is quite relative.
Their reproductive cycle and mating behaviors are similar to the Red-sided Gartersnake.