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Valley Gartersnake

Thamnophis sirtalis fitchi

Family: Colubridae

The Valley Gartersnake is a subspecies of the Common Gartersnake (Thamnophis sirtalis).

COSEWIC status:
  • Not Assessed
SARA status:
  • No Status
IUCN status:
  • Least Concern

Description

The Valley Gartersnake is brown to black with three yellow stripes: one stripe down the back (dorsal stripes) and one on each side (lateral stripes). The lateral stripes are confined to the second and third scale row. This sub-species has pronounced red bars on the sides between the dorsal and lateral stripes. The Valley Gartersnake typically has only seven scales on the upper lip and has a yellowish chin, upper jaw and belly. The top of the head is usually black and the sides of the head often red. Individuals can grow to just over a metre in length.

Similar Species

The Valley Gartersnake may be confused with Terrestrial Gartersnake, the Northwestern Gartersnake and the other two-subspecies of Common Gartersnake that occur in BC, the Puget Sound and Red-sided Gartersnake. The Terrestrial and Northwestern Gartersnakes tend to be lighter in colour and lack the red bars on the sides. Further, the Terrestrial Gartersnake typically has eight scales on the upper lip and has rows of large dark spots that invade the dorsal stripe and give it a jagged or wavy edge. The Valley Gartersnakes range does not overlap with the other sub-species of Common Gartersnake in B.C.

Distribution

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In Canada, the Valley Gartersnake occurs throughout central B.C. north to Hazelton and the Nass River. In the United States this species ranges south along the coast to central California and east to western Wyoming. Including all subspecies, the Common Gartersnake is found throughout much of southern Canada and most of the United States, with the exception of the driest areas in the southwest, and in a small part of northern Mexico.

Habitat

The Valley Gartersnake is a habitat generalist and can be found in a wide variety of habitats, including forests, wetlands, shrublands, shorelines, fields and rocky areas. This species also inhabits many urban and human-dominated landscapes. Valley Gartersnakes are commonly found under cover objects, such as rocks and logs, which provide important microhabitat for shelter and thermoregulation. They overwinter — often communally — below the frost line in mammal burrows, rock crevices, talus slopes, crayfish burrows, anthropogenic structures (e.g. old foundations, cisterns), ant mounts, and other underground cavities.

Biology

Valley Gartersnakes breed in the spring, soon after emerging from hibernation. Females typically give birth to 5–40 live young in July or August. The young are 13–23 centimetres in length at birth and mature in two or three years. This species is the most commonly encountered snake in most parts of its range and adapts well to human modification of the landscape. The Valley Gartersnake primarily forages during the day and eats a wide variety of prey, including frogs, toads, salamanders, earthworms, slugs, small fish, mice and occasionally birds and eggs. This species can live for more than twenty years.

Threats

Road mortality can be a significant threat to Valley Gartersnake populations located near busy roads. Although intensive habitat loss is a threat to all snakes, this species is able to persist in areas with low to moderate human disturbance. Human persecution and subsidized predation may also present a risk to this species in areas of high human density. 

Additional Information About This Species In Canada