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Eastern Gartersnake

Thamnophis sirtalis sirtalis

Family: Colubridae

The Eastern Gartersnake is a sub-species of the Common Gartersnake (Thamnophis sirtalis).

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


The Eastern Gartersnake is highly variable in colour and pattern but tends to have a dark green, brown or black background colour with three yellow stripes: one down the back (dorsal stripe) and one on each side (lateral stripes). The lateral stripes are confined to the second and third scale row, and are sometimes flecked with red. Some individuals have light chequered or speckled patterning, with or without stripes, and melanistic individuals (all black or black back with no stripes) are common in some geographically isolated areas around the Great Lakes (e.g. Pelee and Toronto Islands, Long Point). The Eastern Gartersnake usually has a yellowish chin and upper jaw. The belly is cream to yellow without patterning. Females, which are larger than males, , can grow to over a metre in length.

Similar Species

The black and yellow striped form of the Eastern Gartersnake is very similar to the Butler’s Gartersnake, Red-sided Gartersnake and Eastern Ribbonsnake. The lateral (side) stripes on the Eastern Ribbonsnake are on the third and fourth scale rows. The Ribbonsnakes also has a distinct white crescent in front of the eye, is more slender than the garternakes and has a longer tail. The lateral stripes on the Butler's Gartersnake are on the third and part of the second and fourth scale rows. That species also has a smaller head than the Eastern Gartersnake, making the neck less obvious. The Red-sided Gartersnake has red or orange bars or spots interspersed on the dark background colour on the sides above the yellow lateral stripes. The Red-sided Gartersnake is found only in northwestern Ontario and Manitoba. A melanistic Eastern Gartersnake can be mistaken for a watersnake or small Gray Ratsnake, but both watersnakes and ratsnakes at that size will have faint blotchy patterning and a patterned belly, which the Eastern Gartersnake lacks. Brown-coloured Eastern Gartersnakes may also be mistaken for a Queensnake, which has no light dorsal (centre of back) stripe, several faint dark stripes down its back and a striped belly.


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The Eastern Gartersnake occurs in Ontario and western Quebec. The various sub-species of Common Gartersnake occur 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.


The Eastern Gartersnake is a habitat generalist and can be found in a wide variety of habitats, including forests, wetlands, shrublands, fields and rocky areas. This species also inhabits many urban and human-dominated landscapes. Eastern 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, ant mounds, anthropogenic structures (e.g. old foundations, cisterns) and other underground cavities.


Eastern Gartersnakes generally breed in the spring, soon after emerging from hibernation, but also breed in the fall. In some areas, mating frenzies — involving many individuals — occur near hibernation sites. Females give birth to 10–40 live young in midsummer. 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 can often adapt to human modification of the landscape. The Eastern Gartersnake primarily forages during the day and eats a wide variety of prey, including frogs, toads, salamanders, earthworms, leeches, small fish, mice and occasionally birds and eggs. This species can live for more than twenty years.


The greatest threat to this snake is road mortality; Eastern Gartersnakes are killed in exceptionally high numbers on roads, especially in southern parts of Canada where road density and traffic volume are high. 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