The gray ratsnake is the largest snake in Canada and can grow to 2.5 metres in length. Juveniles are distinctly blotched, but older individuals become increasingly black with only faint patterning. The belly is whitish with black checkerboard markings, and the throat is a uniform cream or white.
Due to its large size and dark coloration, an adult gray ratsnake can be confused with the northern watersnake. Although both have patterning that becomes less distinct with age, the watersnake has distinct banding, whereas the ratsnake is blotched. The belly of the northern watersnake is also whitish but with dark, crescent-shaped spots rather than the checkerboard patterning of the ratsnake. The watersnake lacks white or cream on its throat. Melanistic (black phase) gartersnakes have keeled (ridged) scales, while those of the ratsnake are weakly keeled (the ridges are not very pronounced).
In Ontario, this species inhabits forests and wooded areas but may spend part of the summer in open areas, such as old fields or meadows.
View an interactive map of the known ranges of gray ratsnakes in Ontario.
Gray ratsnakes breed in spring, the females laying their eggs – as many as 24 but more commonly 12 to 16 – in rotting logs or under rocks. The hatchlings, which are 30 to 40 centimetres long, emerge in late summer or early fall.
Although people in Canada generally do not expect to see a two-metre-long snake draped across the branches of a tree, the ratsnake frequently climbs trees to eat birds’ eggs or nestlings. It also eats small mammals and frogs. In eastern Ontario, ratsnakes hibernate communally in rocky outcrops.
The common and scientific species names of this species have changed a number of times over the past few years.
Other names: Scotophis spiloides, Elaphe spiloides, Elaphe obsoleta, Elaphe obsoleta spiloides, central ratsnake, black ratsnake, eastern ratsnake, midland ratsnake
Threats and Trends
The gray ratsnake has disappeared from much of its historic range along the north shore of Lake Erie. The small size of its range and increasing development pressures in southern and eastern Ontario make this species vulnerable to further decline. Ratsnakes occur in areas of high human population and, unfortunately, insensitive people who dislike or fear these harmless but large snakes often kill them. They are also killed on roads.
Current Status and Protection
The Carolinian population of the gray ratsnake is currently listed as Endangered under the Ontario Endangered Species Act, 2007 and Endangered under the federal Species at Risk Act. The Great Lakes–St. Lawrence population of this species is currently listed as Threatened under the Ontario Endangered Species Act, 2007 and Threatened under the federal Species at Risk Act.The species has also been designated as a Specially Protected Reptile under the Ontario Fish and Wildlife Conservation Act. These acts offer protection to individuals and their habitat. The habitat of this species is further protected in Ontario by the Provincial Policy Statement under the Planning Act. The International Union for Conservation of Nature lists the global status of grey ratsnake as Least Concern. The species’ status was last confirmed in January 2010. Additional detail about legal protection for species at risk in Ontario is available on our Legal Protection page.
Learn more about reptile and amphibian conservation and what you can do to help these species on our Reptile and Amphibian Stewardship page.