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)

Systematics: Carolus Linnaeus originally described this snake as Coluber Sipedon in 1758, based on a specimen sent to him by Pehr Kalm from "North America." Schmidt (1953) restricted the type locality to the vicinity of New York City. Rossman and Eberle (1977) changed the generic name from Natrix to Nerodia. Until that time, most authors in the Virginia literature used the genus Natrix for this species (e.g., Dunn, 1918,1936; Richmond and Goin, 1938; Uhler et al., 1939; Conant, 1945; Burger, 1958; Mitchell, 1974b). Cope (1900) included sipedon as a subspecies of N. fasciata (= fasciatus). Subsequent authors have used the current nomenclature. Four subspecies are recognized: N. s. insularum (Conant and Clay), N. s. pleuralis (Cope), N. s. sipedon (Linnaeus), and N. s. williamengelsi (Conant and Lazell). Conant and Collins (1991) illustrated the distributions of these races. Only the nominate subspecies occurs in Virginia.

Description: A moderate- to large-sized snake reaching a maximum total length of 1,405 mm (55.3 inches) (Conant and Collins, 1991). In Virginia, maximum known snout-vent length (SVL) is 1,294 mm (50.9 inches) and maximum total length is 1,374 mm (54.1 inches). Tail length/total length in the Virginia sample was 12.9-29.1% (ave. = 22.9 ± 2.7, n = 239).

Scutellation: Ventrals 125-154 (ave. = 135.2 ± 3.4, n = 358); subcaudals 36-83 (ave. = 66.9 ± 8.2, n = 228); ventrals + subcaudals 173-228 (ave. = 202.3 ± 8.8, n = 228); dorsal scales strongly keeled, scale rows usually 23 (66.7%, n = 330) at midbody, but may be 21-22 (23.9%) or 24-25 (9.4%); anal plate divided; infralabials 10/10 (70.3%, n = 310) or other combinations of 8-12 (29.7%); supralabials 8/8 (88.6%, n = 326) or other combinations of 8-10 (11.4%); loreal scale present; preoculars 1/1; postoculars 3/3; temporal scales 1+3/1+3 (59.6%, n = 322), 1+2/1+2 (21.4%), 1+3/1+2(17.0%), or combinations of 1-4 (1.9%).

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; alternating blotches in contact or separated by 1 scale; body color brown to gray with varying amounts of red, yellow, or white; dorsal blotches and crossbands (24-39, ave. = 30.9 ± 2.5, n = 142) vary from solid black to reddish brown with black borders; venter cream to yellowish, sometimes pinkish, with 2 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 (see "Geographic Variation") ventral pigmentation may consist of 2 dark stripes on either side of midventral line, forming a midventral yellow to cream stripe; head usually uniformly dark brown but may have 1 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.

Sexual Dimorphism: Sexual dimorphism occurs in body size and scutellation. Adult females averaged longer (SVL ave. = 774.3 ± 151.9 mm, 505-1,294, n = 142) and weighed more (ave. = 454.2 ± 239.6 g, 100-1,215, n = 52) than males (SVL ave. = 572.7 ± 98.6 mm, 403-915, n = 119; body mass ave. = 196.1 ± 111.3, 63-555, n = 39). Sexual dimorphism index was 0.35. The average tail length/total length was lower in females (21.3 ± 2.2%, 12.9-26.6, n = 112) than males (24.5 ± 2.2%, 14.8-29.1, n = 110). Males had a greater average number of subcaudals (males 72.6 ± 5.6, 49-83, n = 100; females 61.7 ± 7.0, 36-76, n = 113) and ventrals + subcaudals (males 207.3 ± 6.6, 185-225, n = 100; females 197.7 ± 8.0, 173-222, n = 113). The average number of ventrals was similar between sexes (males 134.7 ± 3.2, 125-148, n = 159; females 135.6 ± 3.5, 127-154, n = 181), as was the number of body blotches and crossbands (males 30.8 ± 2.5, 24-39, n = 69; females 30.9 ± 2.5, 24-35, n = 69).

Juveniles: Juveniles are patterned and colored as adults. At birth, juveniles were 116-193 mm SVL (ave. = 171.3 ± 12.5, n = 100), 158-254 mm total length (ave. = 226.8 ± 16.8), and 3.8-5.5 g body mass (ave. = 4.7 + 0.9, based on means of 8 litters).

Confusing Species: Nerodia sipedon is often confused in Virginia with the venomous Northern Cottonmouth (Agkistrodon piscivorus). The Northern 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 a pit between the eye and nostril. Northern Cottonmouths lack the half-moons on the venter and occur only in southeastern Virginia. Nerodia erythrogaster has a uniformly brown dorsum and red venter as adults, and a plain venter and 6 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.

Geographic Variation: With a few exceptions, the dorsal pattern of this snake is similar throughout Virginia. However, populations in three areas of Virginia possess variations on the description given above. (1) Individuals of N. sipedon occurring in brackish marshes on the Virginia side of the Potomac River between Arlington and Quantico are generally uniformly patterned. They are dark brown dorsally, 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. (2) Many N. sipedon specimens from southwestern Virginia, west of the New River drainage, are patterned dorsally as those in the rest of the state, but lack the halfmoon 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 dark half-moons on either side of the patternless midline. The center along the midline is cream, yellow, or pinkish. (3) Individuals of this species from southeastern Virginia are the most problematic because a number of specimens possess characteristics that suggest identification as the Banded Watersnake (Nerodia fasciata), which occurs in North Carolina and farther south in the Coastal Plain (Conant, 1963; Palmer and Braswell, in press). Nerodia sipedon in the southeastern region had a higher average number of complete body crossbands (12.1 ± 6.4, 2-34, n = 55) than in other regions in the state (aves. range from 5.3 ±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 Appalachian Plateau (ave. = 13.7 ± 4.0, 10-18, n = 4). Many of the southeastern specimens possessed an eye-jaw stripe. The amount of black in the dorsal and ventral patterns was higher than elsewhere in Virginia. Conant (1963) determined that all the water snakes from southeastern Virginia he examined were N. sipedon and that N. fasciata occurred below Albemarle Sound in North Carolina. See "Remarks" for additional comments.

The average total number of body crossbands + blotches varied from 29.8 ± 0.5 (29-30, n = 4) in the northern Blue Ridge Mountains to 32.5 ±1.3 (31-34, n = 4) in the Appalachian Plateau. The number of ventral scales varied from 127-138 (ave. = 133.4 ± 2.6, n = 55) in the upper Coastal Plain to 137-141 (ave. = 138.5 ± 1.7, n = 4) in the Appalachian Plateau. Subcaudal scales averaged from 63.0 ± 4.5 (60-70, n = 4) in the Appalachian Plateau to 69.9 ± 6.1 (60-79, n = 34) in the upper Piedmont, and ventrals + subcaudals averaged from 196.6 ± 10.6 (173-213, n = 27) in the upper Coastal Plain to 206.7 ± 9.5 (182-222, n = 15) in the lower Piedmont.

Biology: Northern Watersnakes are found in a wide variety of habitats in Virginia, including lakes; ponds; rivers; freshwater and tidal creeks; ditches; swamps; freshwater and brackish marshes; and low, wet areas. Any area with moisture available for most of the year will have populations of this snake. They are inconspicuous in habitats with emergent aquatic vegetation. Bulmer (1985) noted that unbanded water snakes from Potomac River marshes were less conspicuous in the turbid water than banded forms. Dunson (1980) determined that N. sipedon from Accomack County were unable to tolerate full-strength seawater but could live in brackish water where the salinities were low. Nerodia sipedon can be found in every month of the year, depending on the weather. Basking individuals are occasionally seen on warm winter days. The primary period of activity is March-October, but this varies depending on location in the state. Activity occurs at night and early morning hours during the summer but at any time of the day at other times of the year. Body temperatures of active N. sipedon taken March-October were 13.0-24.6°C (ave. = 21.6, n = 10; ambient temperatures 13.2-24.0°C), whereas body temperatures of snakes under boards and rocks (all in summer) were 26.0-31.6°C (ave. = 29.6, n = 6; ambient temperatures 24.0-26.0°C). Blem and K. Blem (1990) reported average body temperatures of 25.5°C in nature and 25.6°C in laboratory preference experiments.

Nerodia sipedon is a predator of fish and amphibians, although other prey types are sometimes taken. Uhler et al. (1939) listed the following prey from 30 snakes from the George Washington National Forest: fish-brook trout (Salvelinus fontinalis), northern pike (Esox lucius), sunfish (Lepomis spp.), smallmouth bass (Micropterus dolomieu), brown bullheads (Ameiurus nebulosus), slimy sculpins (Cottus cognatus), mottled sculpins (Cottus bairdi), northern hog suckers (Hypentelium nigricans), and unidentified minnows; amphibians-American Toads (Anaxyrus americanus), Bullfrogs (Lithobates catesbeianus), Green Frogs (Lithobates clamitans), Dusky Salamanders (Desmognathus fuscus), Spring Salamanders (Gyrinophilus porphyriticus), and an unidentified Plethodon, mammals-unidentified mammal hair. To this list I add goldfish (Carassius auratus), tesselated darters (Etheostoma olmstedi), common carp (Cyprinus carpio), Northern Cricket Frogs (Acris crepitans), Southern Toads (Anaxyrus terrestris), Fowler's Toads (Anaxyrus fowleri), Coastal Plains Leopard Frogs (Lithobates sphenocephalus utricularius), Spring Peepers (Pseudacris crucifer), and Bullfrog tadpoles (Lithobates catesbeianus). Dunn (1915e) reported channel catfish (Ictalurus punctatus) as prey. Ernst and Barbour (1989b) summarized the known prey of this species. Each prey is swallowed alive. Predators recorded for this species in Virginia are Eastern Kingsnakes (Lampropeltis getula), raccoons (Procyon lotor), largemouth bass (Micropterus salmoides), and Eastern Snapping Turtles (Chelydra serpentina).

Nerodia sipedon bears living young. Mating has been observed in Virginia between 17 April and 12 June. Mating usually takes place out of the water on snags, logs, and vegetation, as well as 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 Virginia are from 17 August to 12 September. Dunn (1915c) noted a period of 12 August-12 October. Litter size was 11-56 (ave. = 28.5, n = 24). Fitch (1970) reported litter sizes of 8-46 for this subspecies.

This is a commonly encountered snake because of the wide range of habitats in which it occurs. Of the 278 snakes recorded by Clifford (1976) from Amelia County in a 4-year period, 16 were of this species. Uhler et al. (1939) listed 119 water snakes out of a total of 885 from the George Washington National Forest; most were from riverine habitats at low elevations. Martin (1976) found 3 Northern Watersnakes out of a sample of 545 on the Skyline Drive and Blue Ridge Parkway in a 3-year period.

Nerodia sipedon almost always bites repeatedly when captured, especially the adults. Their long teeth, adapted for holding struggling fish, can inflict a minor wound. They also discharge musk from glands at the base of the tail and sometimes eject feces.

Remarks: Other common names in Virginia are water snake and water moccasin (Hay, 1902; Dunn, 1915a), common water snake (Dunn, 1936), dryland moccasin (Burch, 1940), brown banded water snake (Carroll, 1950), banded water snake (Linzey and Clifford, 1981), and moccasin (Brothers, 1992).

Burger (1975) noted the collection of several midland water snakes, Nerodia s. pleuralis, in Lee County. These specimens have apparently been lost. Others collected in the same area and elsewhere in southwestern Virginia were all N. s. sipedon. The potential for intergrades of sipedon and pleuralis still exists, however, and additional study is needed to ascertain if an intergrade zone occurs in southwestern Virginia.

A photograph of a two-headed juvenile N. sipedon from Montgomery County was published in Virginia Wildlife (January 1964, p. 26), and an observation of an albino from New Kent County was reported by Hensley (1959). Albinistic specimens from Roanoke County have been observed but no records have been published. In these snakes, a faint pattern was present but the snakes lacked all dark pigment. R. L. Hoffman (pers. comm.) photographed and released a xanthic specimen he caught in Giles County in June 1988; it lacked dark pigment on the dorsum and venter but had dark pupils.

Palmer and Braswell (1988) reported N. fasciata from near Elizabeth City, North Carolina, about 26 km south of the Virginia-North Carolina line. Hybridization between N. sipedon and N. fasciata may occur in parts of southeastern Virginia, as it apparently does elsewhere (Conant, 1963), causing some specimens in this area to have dark eye-jaw stripes and a nearly complete banded pattern. Additional work on this problem is clearly needed.

Conservation and Management: This species is secure in Virginia. Populations are declining around areas of urban development due to habitat loss and in other areas where some people make a "sport" of shooting them. Education of the public regarding their true identification would help to lessen the killing of individuals mistakenly thought to be "water moccasins," particularly outside the range of Agkistrodon piscivorus. Nerodia sipedon will inhabit most freshwater and some brackish wetlands as long as there are prey and hiding places available.

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