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Canadian Herpetological Society Société d'Herpétologie du Canada |
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Gray Ratsnake
Pantherophis spiloides
Family: Colubridae
The common and scientific names of this species have changed several times recently, and it has also been known as Black Ratsnake and Eastern Ratsnake.
COSEWIC status:- Endangered (Carolinian population)
- Threatened (Great Lakes / St. Lawrence population)
- Endangered (Carolinian population)
- Threatened (Great Lakes / St. Lawrence population)
- Least Concern
Description
The Gray Ratsnake is the largest snake in Canada and can grow to 2.5 m in length. Juveniles have distinct blotches over a tan to grey background colour, but older individuals become increasingly black with only faint light patterning. The belly is whitish with black checkered pattern, and the throat is a uniform cream or white.
Similar Species
An adult Gray Ratsnake can be confused with the Northern Watersnake and melanistic (all black) Eastern Hog-nosed Snake. Although all three have patterning that becomes less distinct with age, if pattern is visible, the watersnake has distinct banding and keeled scales, whereas the ratsnake is blotched. The belly of the Northern Watersnake is also white to yellow but has crescent-shaped markings rather than the checkerboard patterning of the ratsnake. The watersnake lacks white or cream on its throat. Melanistic Eastern Hog-nosed Snakes have a stout body and an upturned snout. Melanistic (black phase) gartersnakes have an unpatterned belly (either black or white) and keeled (ridged) scales, while those of the ratsnake are weakly keeled (the ridges are not very pronounced).
Distribution
Click for larger image
The Canadian distribution of the Gray Ratsnake is limited to two small areas in Ontario: the north shore of Lake Erie and the Frontenac Arch at the eastern end of Lake Ontario. The species occurs throughout much of the eastern United States as far southwest as southern Texas.
Habitat
In Ontario, this species inhabits forest, woodland, savannah and adjacent open habitats, such as forest clearings, rock outcrops, old fields or meadows. Rocks, logs and other cover objects are important microhabitats, as are snags and hollow trees. Individuals overwinter in rock crevices, talus slops along rock outcrops, mammal burrows or anthropogenic structures such as old foundations or wells. Eastern Ratsnakes often overwinter communally and show strong fidelity to their hibernaculum. Eggs are generally deposited in hollow logs and stumps, in piles of vegetation or under rocks.
Biology
Gray Ratsnakes breed in late spring and the females lay 7–23 eggs in late June or August. Females typically only reproduce every two or three years. The hatchlings, which are approximately 30 cm long, emerge in late August to October. In Canada, individuals of this species may not reach maturity until they are 7 years of age, and they can live for 25–30 years. Gray Ratsnakes forage primarily in forest habitat but require open and edge habitats for thermoregulation. Ratsnakes primarily prey on small mammals and birds, and frequently climb trees in search of birds' eggs or nestlings
Threats
The Gray Ratsnake has disappeared from much of its historic range along the north shore of Lake Erie due to extensive conversion of natural habitat to urban and agricultural uses. Much of the Ontario distribution of this species overlaps with areas of high human population density. Consequently, road mortality is a major contributing cause of ongoing population declines. This species is also persecuted by misinformed people who dislike or fear these harmless snakes.