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Canadian Herpetological Society





Société d'herpétologie du Canada



Nerodia sipedon sipedon
Northern Watersnake / Couleuvre d'Eau


Northern Watersnake
Click on image for video of specimens on Pelee Island

The Watersnakes, and other live-bearing, harmless snakes, which were included within the Family Colubridae, have recently been placed in the Family Natricidae.

Description
The Northern Watersnake (N. s. sipedon) is red to brown with alternating dark blotches on the back and sides at the midbody. Older snakes are darker, eventually becoming almost black. The belly is lighter in colour, often white or yellow with dark crescent shaped spots on it. The Lake Erie Watersnake (N. s. insularum) is a subspecies of the Northern Watersnake which is only found on islands and the southern shore of Lake Erie. It is uniformly gray above rather than banded or blotched.

Confusing Species
There are a number of other boldly blotched snakes in eastern Canada. The Northern Watersnake may be confused with the Foxsnake (which has a yellowy background colour), Milksnake (which has a Y- or V-shaped blotch on the back of its head) or the Eastern Hog-nosed Snake (which has an upturned snout). Darker individuals can be confused with the rare Gray Ratsnake, which may be jet black in colour.

Distribution
In Canada, the Northern Watersnake is limited to southern Ontario, south of Lake Superior, and extreme southern Quebec. In the US, it is found as far south as Louisiana and as far west as Oklahoma.

Habitat
The Northern Watersnake can be found in almost any permanent body of freshwater within its range, although the preferred habitat is clear, running streams. They are rarely found more than a few metres from water.

Reproduction
Breeding occurs in the spring after emerging from hibernation. Aggregations of up to 12 males and one female have been reported. Females develop the eggs within their bodies and give birth in later summer or early autumn. In Ontario, females give birth to an average of 23 young. A given clutch of hatchlings often has more than one father. Hatchling size is related to the mother's size, but averages about 18 cm. In Canada, it takes 3-4 years to reach maturity at a size of 50-60 cm. As in many species, young adults may not breed annually.

Natural History
The Northern Watersnake is often found hunting for prey along the water's edge or underwater. It is an excellent swimmer (video)and can be found up to 3 m below the surface of the water and several kilometres from shore. It commonly eats fish and amphibians. Although small prey are usually swallowed head first upon capture, large fish may be carried to shore before being eaten. The Northern Watersnake frequently basks in the open, often in large groups. If captured, it will bite and the wound will generally bleed profusely, because although not poisonous, the saliva contains an anticoagulant. The Northern Watersnake hibernates in groups, sometimes even with other species, in a variety of different sites including burrows, hollow logs, rock piles or muskrat dens.

Conservation Concerns
The Northern Watersnake is widespread and abundant in Canada and is one of the most commonly seen snakes around lakes. The Lake Erie Watersnake, a subspecies found only on islands in the western end of Lake Erie is designated Endangered by COSEWIC, largely due to the population's small size, habitat loss, traffic mortality and persecution by humans.