These are dark-colored snakes, brownish, tan or grayish in appearance. The back and sides have a series of square blotches alternating with each other that may merge to form bands. Adult snakes can appear solid brown or black, especially when dry. The belly is usually white, yellowish, or orangish with dark half-moon-shaped black edges. Juveniles have reddish brown saddles on a tan, brown, or gray background. Males are usually smaller than females. (Behler and King, 1979; Harding, 1997; Jordan, 1929; Tyning, 1990)
Northern water snakes are medium to large snakes, ranging from 61 to 140 cm. They range from 19 to 27.3 cm at birth.
Northern water snakes are found in southern Ontario and the northeastern United States from Nebraska and Kansas in the west to the Atlantic coast and as far south as North Carolina and southern Missouri. (Harding, 1997)
Northern water snakes utilize many different aquatic habitats, such as: rivers, streams, sloughs, lakes, ponds, bogs, marshes, and impoundments. They prefer open areas that provide many spots for them to bask in the sun and relatively still waters. They may move onto land, especially the juveniles, but they never go to far from the aquatic environment. When they are not basking or searching for prey items they can be found beneath flat rocks, logs, boards or other types of cover. Northern water snakes are the most common snakes near water sources throughout northeastern North America. (Harding, 1997)
Male northern water snakes are able to reproduce when they are 21 months old. Female snakes begin to breed when they are three years old and produce a single litter each year. Most reproduction occurs while in or near their hibernation sites between mid-April and mid-June. Temperature and latitude may cause variation in these times. (Bauman and Metter, 1977)
Gestation can last anywhere from 3 to 5 months. Young snakes are born alive (not laid as eggs) from July to September. The litter ranges in size from 4 to 99 offspring. Larger females tend to have larger litters.
Female northern water snakes nurture and protect their young before they are born. Young water snakes become independent at birth, and are capable of hunting and caring for themselves.
Northern water snakes have been known to live up to 9 years and 7 months in captivity. Their lifespan in the wild is unknown.
Northern water snakes are only social during the fall and spring after overwintering. They can be found in groups at basking sites coiled together. For the most part they are solitary animals, especially in the warmer months. It is quite common to find northern water snakes sunning themselves during the warm part of days. They can be found on overhanging branches, walkways, beaver lodges, dried cattail stems, and many shallow areas in the water.)
Northern water snakes can be found during the day or at night, but are more active during the daylight hours. Because of their preference for aquatic habitats they are commonly mistaken for venomous water moccasins, Agkistrodon piscivorous. Northern water snakes are not venomous but they are aggressive and should always be treated with care and respect. (Tyning, 1990)
Northern water snakes probably communicate with each other primarily through touch and smell. They also use their sense of sight and detection of vibrations to locate prey.
Northern water snakes are carnivores and scavengers. They eat a variety of prey items, including amphibians (adults and tadpoles), fish (alive or dead), crayfish, large insects, leeches, other snakes, turtles, birds, and small mammals such as white-footed mice. They have been known to herd schools of fish or tadpoles to the edge of bodies of water where they can prey upon many at one time. Northern water snakes hunt both during the day and at night. They are not constrictors, they simply swallow their prey alive. (Tyning, 1990)
Northern water snakes often escape predators by swimming off across a body of water or by diving below the surface, where they anchor themselves to vegetation or logs. They usually remain submerged for about 5 minutes but are capable of remaining below water for an hour and a half.
When confronted, northern water snakes flatten their bodies and jaws and begin to strike and bite ferociously. They also release a foul-smelling musk and may defecate to discourage predators. When extremely agitated they will also regurgitate their last meal. Northern water snakes are preyed on by large snakes, such as milk snakes and racers, and by raccoons, skunks, and foxes.
Northern water snakes control the populations of their primary prey, including fish, amphibians, and other reptiles.
Northern water snakes could potentially be a problem for fish hatcheries and fish farms. (Harding, 1997)
Contrary to popular belief, northern water snakes are quite beneficial to fish populations. They feed on diseased and dying fish and help to control areas where overpopulation may exist and could stunt fish growth. This may actually help the sport fishing industry. (Harding, 1997)
Northern water snakes are abundant throughout their range.
Snakes of this species are often killed by people who are afraid of them, and confuse them with venomous species, such as rattlesnakes. Northern water snakes will bite if you bother them, but they are not venomous.
Allison Poor (editor), University of Michigan-Ann Arbor.
Merritt Gillilland (author), Michigan State University, James Harding (editor), Michigan State University.
Bauman, M., D. Metter. 1977. Reproductive cycle of the northern water snake, Nerodia sipedon (Reptilia, Serpentes, Colubridae). Journal of Herpetology, 11(1): 51-59.
Behler, J., F. King. 1979. The Audubon Society Field Guide to North American Reptiles and Amphibians. New York: Alfred A. Knoph, Inc..
Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor, Michigan: The University of Michigan Press.
Jordan, D. 1929. Manual of the Vertebrate Animals. New York: World Book Company.
Tyning, T. 1990. Stokes Nature Guides: A guide to Amphibians and Reptiles. Boston, MA: Little, Brown and Company.