Description: The common watersnake can grow up to 4 ft 5 inches in total length (including tail). Per one study, the average total length of females was 2 ft 8 inchces, while that of males was 2 ft 3+1/2 inches. From known studies of this species in the wild, adult females can weigh between 5+1/2 and 14+1/2 ounces typically, while the smaller male can range from 2+7/8 to 5+3/8 ounces. The largest females can weigh up to 20 ounces while the largest males can scale 13 ounces.
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; killing 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.
Habitat:N. sipedon inhabits streams, lakes, and ponds, as well as wetlands. Juveniles typically inhabit lower-order streams adjacent to the larger-order waterways where adults are found. This helps juveniles to avoid predators such as fish, birds, and turtles present in large water bodies.
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. In 2007 an introduced population was discovered in California, where the related species N. fasciata has been introduced since at least 1992.
Diet: They feed primarily on fish, but also frogs, toads, salamanders, insects, crayfish, and rarely mice and shrews.
Reproduction: The common watersnake mates from April through June. It is ovoviviparous (live-bearing), which means it does not lay eggs like many other snakes. Instead, the mother carries the eggs inside her body and gives birth to free-living young, each one 7+1/2–9 inches long. A female may have as many as 30 young at a time, but the average is eight. They are born between August and October. Mothers do not care for their young. Multiple mating by females is common, leading to a focus in sperm competition. Research suggests successful males are not the ones who dedicate more energy to size, but to sperm.
Status: Listed as Least Concern in view of its wide distribution, tolerance of habitat modification, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.
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Disclaimer: ITIS taxonomy is based on the latest scientific consensus available, and is provided as a general reference source for interested parties. However, it is not a legal authority for statutory or regulatory purposes. While every effort has been made to provide the most reliable and up-to-date information available, ultimate legal requirements with respect to species are contained in provisions of treaties to which the United States is a party, wildlife statutes, regulations, and any applicable notices that have been published in the Federal Register. For further information on U.S. legal requirements with respect to protected taxa, please contact the U.S. Fish and Wildlife Service.