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Northern Watersnake

Nerodia sipedon sipedon

Family: Colubridae

The Northern Watersnake is a subspecies of the Common Watersnake (Nerodia sipedon).

COSEWIC status:
  • Not Assessed
SARA status:
  • No Status
IUCN status:
  • Least Concern

Description

Northern Watersnakes are grey, brown or dark brown with faint alternating darker (sometimes reddish—particularly after shedding) horizontal banding on the back and sides. Young snakes are greyish with pronounced banding, and they become darker as they age until the patterning can often barely be seen and the snake takes on an almost black appearance. The belly is lighter in colour, often white or tan with dark red, tan or brown crescent-shaped spots. The scales of this species are keeled (ridged down the centre), which gives the snake a rough, rather than a shiny, appearance. Females are larger than males and can grow to over a metre in length, but most are smaller than that. Large adults can appear quite robust.

Similar Species

The Northern Watersnake may be confused with the Gray Ratsnake, Eastern Foxsnake, Eastern Milksnake, Eastern Hog-nosed Snake, Massasauga and Lake Erie Watersnake. Adult Gray Ratsnakes are black with faint blotches, whereas Northern Watersnakes are dark brown with faint banding. Adult Eastern Foxsnakes have a yellow to light brown body with brown blotches down the back and two alternating rows of smaller blotches along the sides. The Eastern Milksnake has red or reddish brown blotches along its back and sides with a distinct black outline around each blotch. The Eastern Hog-nosed Snake has a distinct upturned snout. The Massasauga usually has a rattle on a blunt tail, a vertical pupil and a triangular head, though Northern Watersnakes will sometimes flatten out their body and head, giving the appearance of a more triangular shape. Distinguishing Northern Watersnakes from Lake Erie Watersnakes can be difficult, but their ranges do not overlap.

Distribution

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The Northern Watersnake is widespread and abundant within its range in Canada and is one of the most commonly seen snakes around lakes. In Canada, the Northern Watersnake is limited to southern Ontario, south of Lake Superior, and extreme southern Quebec. The four subspecies of Common Watersnake occur throughout the northeastern and central United States as far south as the Florida Panhandle and as far west as Colorado.

Habitat

Northern Watersnakes inhabit the shorelines of permanent bodies of fresh water, including lakes, rivers and wetlands. Rocks, logs and other debris are important microhabitats that are used for thermoregulation and retreat sites. This species can often be seen conspicuously basking on shoreline embankments, vegetation mats, logs and branches and other sites that offer quick retreat to the safety of water. Northern Watersnakes hibernate underground in mammal burrows and rock crevices or in beaver and muskrat lodges.

Biology

This species breeds in May and June and females give birth to 13–46 (average of 27) live young in late summer or early fall. The size of the hatchlings is related to the mother’s size but averages about 18 cm. Male Northern Watersnakes reach sexual maturity in two years and females in three. Females typically reproduce each year and this species can live for over 10 years. The Northern Watersnake eats fish and amphibians, hunting for its prey along the water’s edge or underwater. It is an excellent swimmer and can be found up to 3 m below the surface of the water and several km from shore. Although this snake usually swallows small prey head first upon capture, it may carry large fish to shore before consuming them. The Northern Watersnake is curious and may approach swimmers as it investigates the source of ripples in the water (which could be from a fish or other prey). Northern Watersnakes are harmless but will bite in self-defence if they are captured. Their bite can cause mild bleeding because the snake’s saliva contains an anticoagulant.

Threats

Habitat loss, road mortality and persecution by humans are the most significant threats to the Northern Watersnake. Waterfront construction and development, as well as water pollution, affect both its habitat and food sources.

Additional Information About This Species In Canada