American Bullfrog

Eastern gartersnake Joe Crowley

Eastern Gartersnake
(Thamnophis sirtalis sirtalis)

Other names: common gartersnake, Coluber sirtalis

The gartersnakes, and other harmless snakes that bear live young, were included in the family Colubridae but recently have been placed in the family Natricidae.

Characteristics

The eastern gartersnake is highly variable in colour and patterning but tends to be dark green to black with three yellow stripes: one down the back and one on each side, on the second and third scale row. Some individuals have whitish chequered or speckled patterning along the back, and melanistic individuals (black back with no stripes) are very common in some regions (such as on Pelee Island). The eastern gartersnake has a yellowish chin and belly. This species can grow to over a metre in length.

Similar Species

The eastern gartersnake is very similar to the Butler’s gartersnake, red-sided gartersnake and northern ribbonsnake. The lateral (side) stripes on the northern ribbonsnake are on the third and fourth scale rows. That species 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 between the back and lateral stripes. Although many eastern gartersnakes can also exhibit strong reddish colouration, the red often occurs on the chin and along the body below the lateral stripe, and these snakes lack red bars or spots along the back. The red-sided gartersnake is found only in northwestern Ontario.

A melanistic eastern gartersnake can be mistaken for a watersnake or small eastern ratsnake, but both watersnakes and ratsnakes have faint patterning, which the eastern gartersnake lacks. It may also be mistaken for a queen snake, which has two yellowish lateral stripes and several faint dark stripes down its back.

Habitat

The eastern gartersnake is a habitat generalist and can be found in a wide variety of habitats, including forests, shrublands, wetlands, fields and rocky areas. This species also inhabits many urban and human-dominated landscapes. 

 

Biology

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 typically give birth to 10 to 30 live young in midsummer. Up to 85 young have been reported from one female! The young are 13 to 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 eastern gartersnake eats a wide variety of food, including frogs, toads, salamanders, earthworms, small fish and mice. It hibernates underground in burrows, rock outcroppings or the foundations of old buildings. In some areas, hundreds or even thousands of eastern gartersnakes hibernate communally.

Threats & Trends

The eastern gartersnake is widespread and abundant in Ontario and has demonstrated the ability to persist in many human-modified landscapes. The greatest threat to this snake is road mortality; eastern gartersnakes are killed in exceptionally high numbers on roads throughout Ontario. Seeing 10 to 15 dead gartersnakes on the road during an hour of driving on a nice summer day is not uncommon.

Current Status & 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 eastern gartersnake. The species has no protection under the Ontario Fish and Wildlife Conservation Act and is not listed by the International Union for Conservation of Nature.

Learn more about reptile and amphibian conservation and what you can do to help these species on our Reptile and Amphibian Stewardship page.

 

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Range

To view an interactive map of the known ranges of eastern gartersnakes in Ontario, click here.

The eastern gartersnake occurs in Ontario and western Quebec and is the most wide-spread reptile in Ontario, ranging into the northern reaches of the province. The eastern gartersnake and subspecies of it occur throughout most of the United States, with the exception of the driest areas in the southwest.

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