Common Watersnake

The common watersnake (Nerodia sipedon) is a species of large, nonvenomous, common snake in the family Colubridae. The species is native to North America. It is frequently mistaken for the venomous cottonmouth (Agkistrodon piscivorus).

Common names

Common names for N. sipedon include banded water snake, black water adder, black water snake, brown water snake, common water snake, common northern water snake, eastern water snake, North American water snake, northern banded water snake, northern water snake, spotted water snake, streaked snake, water pilot, and water snake.

Description

The common watersnake can grow up to 135 cm (4 ft 5 in) in total length (including tail). Per one study, the average total length of females was 81.4 cm (2 ft 8 in), while that of males was 69.6 cm (2 ft 3+1⁄2 in). From known studies of this species in the wild, adult females can weigh between 159 and 408 g (5+1⁄2 and 14+1⁄2 oz) typically, while the smaller male can range from 80.8 to 151 g (2+7⁄8 to 5+3⁄8 oz). The largest females can weigh up to 560 g (20 oz) while the largest males can scale 370 g (13 oz).

N. sipedon can be brown, gray, reddish, or brownish-black. It has dark crossbands on the neck and dark blotches on the rest of the body, often leading to misidentification as a cottonmouth or copperhead by novices. As N. sipedon ages, the color darkens, and the pattern becomes obscure. Some individuals become almost completely black. The belly also varies in color. It can be white, yellow, or gray; usually, it also has reddish or black crescents.

The common watersnake is nonvenomous and harmless to humans, but superficially resembles the venomous cottonmouth. It is often killed by humans out of fear; attempting to kill snakes greatly increases the chance of being bitten. The two can be easily distinguished: the watersnake has a longer, more slender body and a flattened head the same width as the neck, round pupils, and no heat-sensing pits. The cottonmouth has a fatter body, a wedge-shaped head with prominent venom glands that are wider than the neck, cat-like pupils, and heat-sensing pits between the eyes and the nostrils.

Subspecies

These four subspecies are recognized as being valid:

Nota bene: A trinomial authority in parentheses indicates that the subspecies was originally described in a genus other than Nerodia.

Geographic range

The common watersnake is found throughout eastern and central North America, from southern Ontario and southern Quebec in the north, to Texas and Florida in the south. The northern watersnake (Nerodia s. sipedon) naturally occurs as far west as Colorado, east of the Rocky Mountains, and is commonly found in riparian ecosystems along river systems, such as the South Platte River and Arkansas River. In 2007 an introduced population was discovered in California, where the related species N. fasciata has been introduced since at least 1992.

Introduction