The red-sided gartersnake (Thamnophis sirtalis parietalis) is variable in colour but normally is dark green to black with three yellow stripes: one down the back and one on each side, on the second and third scale row. Between the yellow stripes down the back and sides are vertical red or orange bars. This species can grow to 45 to 80 centimetres in length.
The red-sided gartersnake is very similar to the eastern gartersnake (of which it is a subspecies), Butler’s gartersnake and northern ribbonsnake. In Ontario, the red-sided gartersnake occurs only in the northwest, and neither the ribbonsnake nor Butler’s gartersnake occur that far north. Although many eastern gartersnakes exhibit strong reddish colouration, their red patterning often occurs on the chin and along the body below the lateral (side) stripes, whereas the red-sided gartersnake has red bars or spots between the dorsal (back) and lateral stripes.
The red-sided gartersnake is a habitat generalist and, during its active season, occupies habitat similar to that of the eastern gartersnake – forests, shrublands, wetlands, fields and rocky areas. High-quality hibernation sites that are deep and below the frost line are crucial for this snake, because its range reaches further north than that of any other land-dwelling reptile in Canada.
View an interactive map of the known ranges of red-sided gartersnakes in Ontario.
Red-sided 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, among which many males compete for access to a few females – occur near hibernation sites. Females typically give birth to five to 27 live young in midsummer but have been recorded as having up to 50 young! The young are 19 to 23 centimetres long at birth and mature in two or three years.
Red-sided gartersnakes overwinter in deep crevices formed in rock and in sinkholes in grassy pastures.
These snakes primarily eat frogs and leeches.
Other names: Coluber parietalis
Threats and Trends
This subspecies of the eastern gartersnake is abundant in its northern Ontario range and is able to persist in many human-modified landscapes. The greatest human-induced threat to this species is road mortality, especially during the period of emergence and dispersal when snakes travel great distances and cross roads. Because these snakes hibernate in large groups, occasional events, such as flooding of the den and freezing due to limited snow cover, can result in mass mortality. Although infrequent, these events are responsible for much more mortality than all other threats (e.g., road kill, predation) combined.
Current Status and Protection
Neither the Committee on the Status of Species at Risk in Ontario nor the Committee on the Status of Endangered Wildlife in Canada has assessed the status of the red-sided gartersnake. The species has no protection under the Ontario Fish and Wildlife Conservation Act. The International Union for Conservation of Nature has not yet assessed the red-sided gartersnake, but lists the common gartersnake (of which the red-sided gartersnake is a subspecies) as Least Concern. The common gartersnake’s status was last confirmed March 2007.
Learn more about reptile and amphibian conservation and what you can do to help these species on our Reptile and Reptile and Amphibian Stewardship page.
What You Can Do
- Report a sighting
- Get involved in reptile and amphibian conservation on your property, on the road and in your community
- Donate to support reptile and amphibian conservation
- Watch for reptiles and amphibians on the road
- Don’t release pet reptiles and amphibians into the wild
- Read more about the red-sided gartersnake in the Ontario Reptile and Amphibians Atlas publication.