Features: The Eastern Ratsnake (Elaphe obsoleta), also known as the Gray Ratsnake, is Ontario's largest snake, attaining a length of 200 centimetres or more. Adults are shiny black, with a white chin and throat, while young snakes are grey with dark blotching on the body and tail. They are constrictors and feed mostly on rodents or birds, although frogs and other snakes are also eaten.

The two Canadian populations of Eastern Ratsnake were originally considered to be one species, however based on the fact that the populations are genetically distinct and geographically isolated from one another, the species was split into two subspecies – the Great Lakes-St. Lawrence population and the Carolinian population - in April 2007. The status for the two populations is different, with the Carolinian population being Endangered Nationally, and the Great Lakes-St Lawrence population being Threatened Nationally.

The two populations have different habitat preferences. The Great Lakes/St. Lawrence population prefers edge habitats, particularly old fields next to deciduous forest, and can often be found in hollow logs or rock crevices, or basking on bedrock outcrops. The Carolinian population prefers wooded areas, although they may be found in meadows and fields.

These snakes are excellent climbers, and you may encounter one up a tree or bush hunting for prey. From October to April, they overwinter in underground, communal hibernacula. Hibernacula are usually in warmer, south-facing slopes and may contain many snakes belonging to several species.

Status: Threatened Provincially, Threatened and Endangered Nationally

Range: The Eastern Ratsnake ranges across much of eastern North America, from New England south to Georgia, and west to Texas. In Canada, the Great Lakes/St. Lawrence population occurs in a region of eastern Ontario that includes Frontenac, Leeds and Grenville Counties. The Carolinian population occurs in small sections of Carolinian forest along the northern edge of Lake Erie. Range Maps

Threats: In the Great Lakes-St. Lawrence region, Eastern Ratsnake habitat is threatened as land is developed for recreational use and roads are built. Not only has this fragmented the population, but road deaths have contributed to the species’ decline. Predation by raccoons (which eat eggs) and hawks (which prey especially on young snakes) are additional pressures on this population. Loss of habitat has been the main threat to the Carolinian population of Eastern Ratsnake. The northern shores of Lake Erie are dominated by agriculture and roads, which have severely fragmented this population’s habitat. In addition, high incidences of mortality due to road deaths could reduce the number of individuals below what is considered necessary for the population to survive.

Protection: Ontario's Endangered Species Act that came into effect in June, 2008 now protects the Eastern Ratsnake. The species is also protected by Ontario's Fish and Wildlife Conservation Act. The federal Species at Risk Act (SARA) protects the Eastern Ratsnake on the federal lands on which it occurs. One of the key measures identified for this species is identification and protection of the hibernacula, which are used year after year by the snakes.

Text Sources: COSEWIC 2007; MacCulloch 2002; Prior and Weatherhead 1996

Last Modified Date: October 2008