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Canadian Herpetological Society Société d'Herpétologie du Canada |
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Puget Sound Gartersnake
Thamnophis sirtalis pickeringii
Family: Colubridae
The Puget Sound Gartersnake is a subspecies of the Common Gartersnake (Thamnophis sirtalis).
COSEWIC status:- Not Assessed
- No Status
- Least Concern
Description
The Puget Sound Gartersnake is dark grey to black with three yellow or bluish-grey stripes: one narrow stripe down the back (dorsal stripe) and one on each side (lateral stripes). The lateral stripes are confined to the second and third scale row. Unlike the other subspecies of the Common Gartersnake that occur in B.C., the red bars on the sides between the dorsal and side stripes are often very faint or absent. The Valley Gartersnake typically only has seven scales on the upper lip and has a yellowish chin and belly. Individuals can grow to just over a metre in length.
Similar Species
The Puget Sound Gartersnake may be confused with Terrestrial Gartersnake, the Northwestern Gartersnake and the other two-subspecies of Common Gartersnake that occur in B.C., the Valley and Red-sided Gartersnakes. 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 often invade the dorsal stripe and give it a jagged or wavy edge. The Puget Sound Gartersnake’s range does not overlap with the other sub-species of Common Gartersnake in B.C.
Distribution
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This Puget Sound Gartersnake has a limited geographic distribution. It is restricted to Vancouver Island and the adjacent mainland coast in Canada and to Northwestern Washington. Including all subspecies, the Common Gartersnake is found throughout 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 Puget Sound Gartersnake is a habitat generalist and can be found in a wide variety of habitats, including forests, wetlands, shrublands, wetlands, shorelines, fields and rocky areas. This species also inhabits many urban and human-dominated landscapes. Puget Sound 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, crayfish burrows, anthropogenic structures (e.g. old foundations, cisterns), ant mounts and other underground cavities.
Biology
Puget Sound 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 cm 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 Puget Sound 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 Puget Sound 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.