Northern Watersnake
Nerodia sipedon sipedon

** Harmless **

Common Name:

Northern Watersnake

Scientific Name:

Nerodia sipedon sipedon



Nerodia is derived from the Greek words neros meaning "flowing" or "liquid" and dia meaning "through".


sipedon is derived from the Greek word sepedon which means "a serpent whose bite causes mortification".


sipedon is derived from the Greek word sepedon which means "a serpent whose bite causes mortification".

Vernacular Names:

Banded watersnake, black watersnake, moccasin, mud moccasin, spotted water adder, spotted water snake, water adder, water viper

Average Length:

24 - 42 in. (61-106.7 cm)

Virginia Record Length:

54.1 in. (137.4 cm)

Record length:

55.3 in. (140.5 cm)

PHYSICAL DESCRIPTION: This species is from 24-42 inches long, a large water snake. It has dark crossbands on the neck and foreparts of the body, but alternating dorsal and lateral blotches on the rest of the body. The dark markings are wider than the spaces between them. There are black or reddish half-moons on the belly. The adults tend to darken so that the pattern becomes obscure. It may disappear altogether, resulting in a plain black or dark brown serpent (putting specimen in water will often reveal pattern details in what seems like a virtually unicolor snake). Half-moons on the belly may be arranged in a regular pattern, scattered at random, represented by dusky areas, or they may be entirely absent. Some specimens have their bellies almost uniformly stippled with gray, except for a yellow, orange, or pinkish mid-ventral stripe. The underside of the tail is patterned virtually to the tip. The scales are keeled *882*. In Virginia, maximum known SVL is 1294 mm (50.9 in.) and maximum total length is 1374 mm (54.1). Tail length/total length ratio is 12.9-29.1 (avg. = 22.9+/-2.7, n=239). Outside Virginia, the maximum known total length is 55.125 inches *11523*.

COLORATION and PATTERN: dorsum of body and tail with a variable number of complete, closely spaced, dark crossbands anteriorly that break up at about midbody to form a series of rectangular, alternating, middorsal and lateral blotches; the alternating blotches in contact or separated by one scale; body color brown to gray with varying amounts of red, yellow, or white; the total number of dorsal blotches and crossbands (24-39, avg. = 30.0+/-2.5, n=142) varies from solid back to reddish brown with black borders; venter cream to yellowish, sometimes pinkish, with two irregular rows of dark half-moons on the ventral scales; half-moons vary from all black to reddish and tan in the center with black borders; shape of markings highly irregular among individuals; in some areas, ventral pigmentation may consist of two dark stripes on either side of the midventral line, forming a midventral yellow to cream stripe; head usually uniform dark brown, but may have one or more dark stripes on a reddish-brown background in some areas; chin usually cream; labial scales light brown, reddish, or yellowish brown and bordered by black or dark brown; reds and yellows fade to cream in preservative. This is a heavy-bodied snake with a rounded, chunky head.*10760*

SEXUAL DIMORPHISM: Sexual dimorphism occurs in body size and scutellation. Adult females average longer (SVL avg. = 774.3+/-151.9 mm, 505-1294, n=142) and weigh more (avg. = 454.2+/-239.6 g, 100-1215, n=52) than males (SVL avg. = 572.7+/-99.6 mm, 403-915, n=119; mass avg. = 196.1+/-111.3, 63-555, n=39).

JUVENILES: Juveniles are patterned and colored as adults. At birth, juveniles are 116-193 mm SVL (avg. = 171.3+/-12.5, n=100), 158-254 mm total length (avg. = 226.8+/-16.8), and 3.8-5.5 grams body mass (avg. = 4.7+/-0.9, n=means of 8 litters).*10760*

CONFUSING SPECIES: Nerodia sipedon is often confused in Virginia with the venomous cottonmouth or "water moccasin" (Akistrodon piscivorus). The cottonmouth has broad crossbands that occur as such along the entire length of the body, a large, angular head (sharp angle from dorsal to lateral in front of the eyes), vertical pupils, and pit between the eye and nostril. Cottonmouths lack the half-moons on the venter and occur only in southeastern VA. Nerodia erythrogaster has a uniform brown dorsum and red venter as adults, and a plain venter and six or fewer complete anterior body crossbands in juveniles. Nerodia taxispilota is brown with a series of alternating dorsal and lateral dark brown blotches along the entire body.*10760*

GEOGRAPHIC VARIATION: With a few exceptions the dorsal pattern of this snake is similar throughout VA. However, populations in 3 areas of VA. possess variations different from that described above. 1) The N. sipedon occurring in brackish marshes on the VA. side of the Potomac River between Arlington and Quantico are generally uniformly patterned. They are colored dark brown dorsally and are nearly patternless and white or cream-colored ventrally. A series of 46 juveniles from a patternless female contained 30.4% with a dorsal pattern and 69.6% without.*10760* 2) Many of the N. sipedon from southwestern VA. west of the New River drainage are patterned dorsally as those in the rest of the state, but lack the half moon pattern on the venter. Of the 42 snakes examined from this area, the ventral patterns of 81% consisted of a peppered stripe or series of half dark moons on either side of the patternless midline. The center along the midline is cream, yellow, or pinkish.*10760* 3) The N. sipedon from southeastern VA. are the most problematic because a number of specimens possess characteristics that suggest identification as the banded water snake (Nerodia fasciata) which occurs in N. Carolina and farther south in the Coastal Plain. Nerodia sipedon in the southeastern region has a higher average of complete body crossbands (12.1+/-6.4, 2-34, n=55) than in other regions in the state (avg. range 5.33+/-1.2 [4-6, n=3] in the Ridge and Valley north of the New River to 8.7+/-4.5 [2-32, n=30] in the northern Piedmont), except the Cumberland Plateau (avg. = 13.7+/-4.0, 10-18, n=4). Many of the southeastern specimens possess an eye-jaw stripe. The amount of black in the dorsal and ventral patterns is higher than elsewhere in Virginia. Conant determined that all the watersnakes from southeastern VA. he examined were N. sipedon and the N. fasciata occurred below Albemarle Sound in North Carolina.*10760*

REPRODUCTION: This species will emerge from hibernation in late March or April and mate soon thereafter *1008*. Mating may occur on branches or rocks over or near water *2075*. The female gives birth in a sheltered spot, such as under a large, flat stone *1008*. There are up to 70 young *1008*, from 7.5-9.0 inches long *882*. They are born in late August, September, or early October *1008*. Hibernation is from October to March *2075*, in the burrows of muskrat, crayfish, meadow mouse, old rock dams, or rock piles near the water *2075*. Nerodia sipedon bears living young. Mating has been observed in VA. between 17 April and 12 June. Mating usually takes place out of the water on snags, logs, and vegetation, and on the ground. The smallest mature female measured was 505 mm SVL and the smallest mature male was 403 mm SVL. Records of birth in VA. are from 17 August to 12 Sept. Litter size is 11-56 (avg. = 28.5, n=24).*10760*

BEHAVIOR: This species will hide and bask by day and forage by night *1008*. They are less active on cloudy days than sunny days *2065*, and most active from May-July *2065*. This species will hide under flat stones at or near the water's edge, or under the edge of a waterway's banks *2065*. They bask on logs, branches, driftwood, or banks near water *883*. This species prefers permanent aquatic habitats *1013*. It resides in virtually every swamp, marsh, bog, stream, pond, or lake border within its range *2065,2082,2083*. They are occasionally found in the woods near water, but prefers sunny areas to dense shaded locations *949*. They may follow waterways into urban areas *949*. The home range is limited and they tend to stay in one pond *2082*. Repeated trapping indicates movement of less than 100 yards *2083*. They occasionally traverse large bodies of water *2065*. Nerodia sipedon almost always bites repeatedly when captured, especially the adults. Their long teeth adapted for holding struggling fish, can inflict a nasty wound. They also discharge musk from glands at the base of the tail and sometimes eject feces. Many were on roads, but most have been basking on banks or in tree branches over water. Thorp has also observed that this species is more nervous than cottonmouths (Agkistrodon piscivorus) or brown watersnakes (Nerodia taxispilota) and that this species will flee to the water quickly when approached, with the exception of cool mornings in spring *11523*. or brown watersnakes

AQUATIC/TERRESTRIAL ASSOCIATIONS: This species is associated with Hyla sp., Lithobates catesbeiana, crayfish, fish, Notophthalmus viridescens, Heterodon platyrhinos, Coluber constrictor, Thamnophis sirtalis, Regina septemvittata, Thamnophis sauritus and Terrapene carolina. Plant associations are unknown *2065,2075*. Thorp has observed predation on this species by a cottonmouth (Agkistrodon piscivorus) *11523*.

LIMITING FACTORS: The longevity record for this species is 9 years and 7 months *11523*.

References for Life History

  • 882 - Conant, R., 1958, A field guide to reptiles and amphibians of the United States and Canada east of the 100th Meridian, 366 pgs., Houghton Mifflin Co., Boston, MA
  • 883 - Conant, R., 1975, A field guide to reptiles and amphibians of Eastern and Central North America, 429 pgs., Houghton Mifflin Co., Boston, MA
  • 949 - Minton, S.A., 1972, Amphibians and Reptiles of Indiana, Indiana Academy of Science Monograph, Vol. 3, 346 pgs., Indiana Academy of Science, Indianapolis
  • 1008 - Barbour, R.W., 1971, Amphibians and reptiles of Kentucky, 334 pgs., Univ. of Kentucky Press, Lexington, KY
  • 1013 - Jackson, J.J., 1983, Snakes of the Northeastern United States, 111 pgs., Ext. Serv., Univ. of GA, Athens, GA
  • 2065 - Conant, R., 1938, The reptiles of Ohio, Am. Midl. Nat., Vol. 20, pg. 1-200
  • 2075 - Wright, A.H., Wright, A.A., 1957, Handbook of snakes of the United States and Canada, Vol. 1, 564 pgs., Comstock Publ., Ithaca, N.Y
  • 2082 - Fraker, M.A., 1970, Home range and homing in the watersnake, Natrix sipedon sipedon, Copeia, Vol. 1970, Num. 4, pg. 665-673
  • 2083 - Brown, E.E., 1940, Life history and habits of the northern water snake, Natrix sipedon sipedon, Ph.D. Dissertation, Cornell Univ., Ithaca, N.Y.
  • 10760 - Mitchell, J. C., 1994, The Reptiles of Virginia, 352 pgs., Smithsonian Institution Press, Washington, DC
  • 11523 - Thorp, T.J., 2001, Personal Communication, Expert Review for GAP Analysis Project, Three Lakes Nature Center and Aquarium


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