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Canadian Herpetological Society Société d'Herpétologie du Canada |
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Eastern Ribbonsnake
Thamnophis saurita
Family: Colubridae
The sub-species of Eastern Ribbonsnake that occurs in Canada is the Northern Ribbonsnake (Thamnophis sauritus septentrionalis).
COSEWIC status:- Threatened (Atlantic population)
- Special Concern (Great Lakes population)
- Threatened (Atlantic population)
- Special Concern (Great Lakes population)
- Least Concern
Description
The Eastern Ribbonsnake is black with three yellow stripes: one down the back (dorsal stripe) and one on each side (lateral stripes). The lateral stripes are on the third and fourth scale rows. It has a distinct white crescent in front of the eye, a white chin, a whitish yellow belly and often rust-coloured sides. This species is long and narrow, and the tail makes up approximately one-third of its total length. Individuals can grow to almost a metre in length but are usually considerably shorter.
Similar Species
The Eastern Ribbonsnake is similar to the Eastern Gartersnake, Butler’s Gartersnake and Red-sided Gartersnake. Those three species lack the white crescent in front of the eye and their chin is more yellow than white. Compared with those species, the Eastern Ribbonsnake is more brightly patterned, slender and has a longer tail. The lateral (side) stripes on the Eastern Gartersnake are confined to the second and third scale rows, and the lateral stripes on the Butler's Gartersnake are on the third and part of the second and fourth scale rows. The range of the Red-sided Gartersnake does not overlap with that of the Eastern Ribbonsnake.
Distribution
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The Eastern Ribbonsnake occurs in two disjunct populations in Canada. The larger population is in southern Ontario and a small part of Quebec, and the second, smaller population in Nova Scotia. The various subspecies of the Eastern Ribbonsnake occur throughout the eastern United States, whereas the Northern Ribbonsnake subspecies ranges from Maine west to Michigan and Wisconsin.
Habitat
The Eastern Ribbonsnake is semi-aquatic and inhabits wetlands and the shorelines of lakes and rivers. This species also relies on upland habitat, typically forest, for overwintering and birthing sites. They overwinter – often communally – below the frost line in mammal burrows, rock crevices, crayfish burrows, ant mounds and muskrat lodges.
Biology
Eastern Ribbonsnakes breed in the spring after emerging from hibernation, although fall mating may occur as well. Females give birth to 2–26 live young in late summery, although 9–12 is more common. The young are 16–24 cm long at birth and reach maturity in two to three years. Eastern Ribbonsnakes spend much of their time in or near water, where they feed primarily on amphibians, especially frogs. Ribbonsnakes bask along shorelines in the vegetation, on logs or, occasionally, in low shrubs. When startled, these snakes often move into the water, where they can elude most predators. Natural longevity is unknown, but a captive-born individual lived almost 11 years.
Threats
The loss of most wetland habitat in southern Ontario is the primary reason for the decline of this species, and ongoing habitat loss continues to threaten it. Pollution, such as agricultural runoff, has severe negative effects on amphibian populations, and the loss of amphibian populations may cause the decline or disappearance of ribbonsnakes. Road mortality is also a threat to this species when roads bisect aquatic habitats, and human persecution likely occurs in many areas.