Reptiles of North Carolina

Scientific Name:	Common Name:		Family (Alpha):

NC Records
Colubridae Members:
Nerodia fasciata - Southern Watersnake

Photo: C. Teague

Photo: M. Shields

Taxonomy

Class: Reptilia

Order: Serpentes

Family: Colubridae

Subfamily: Natricinae

Other Common Name(s): Banded Water Snake


Taxonomic Comments: Nerodia, as currently considered, consists of ten species of semiaquatic, moderately large natricid snakes native to eastern and central North America, ranging from southern Canada down to the Gulf Coast of Mexico. For some time, North American members of this genus were considered part of the genus Natrix; Rossman and Eberle (1977) restricted Natrix to European taxa and resurrected Nerodia for North American species.
Species Comments: Nerodia fasciata, the Southern Watersnake, is one of four Nerodia in North Carolina. This species is distributed down the southeastern United States, from northern North Carolina to southern Florida, along the Gulf of Mexico, then ranging north up the Mississippi River to east Texas. In North Carolina, the species ranges down the Coastal Plain, though it is largely absent from the Outer Banks. This species occurs in a broad area of introgression with N. sipedon along the Fall Line, as well as in parts of the Coastal Plain. Some individuals in these areas cannot be morphologically assigned to one or the other species (Mebert, 2008). Some authors recognize three subspecies; North Carolina specimens are all assigned to the nominate subspecies N. f. fasciata, the Banded Watersnake. Further taxonomic work is needed to determine whether the evolutionary history of these species matches the current subspecific designations. The generic epithet Nerodia is derived from the Greek neros, "flowing" or "liquid", and dia, "through". The specific epithet fasciata is derived from the Latin fascia, "a bundle or band". Taxonomic References: Gibbons and Dorcas (2004); Mebert (2008).

Identification

Description: Southern Watersnakes are large, heavy-bodied aquatic snakes. Adult dorsal color is highly variable, but typically is varying shades of brown or gray with reddish to dark brown crossbands down the body; these crossbands are widest middorsally, narrowing laterally. A dark bar is usually apparent from the posterior orbit to the posteriormost supralabial. The venter is varying shades of white, yellow, or reddish, with dark spots or transverse lines.

Morphological Features: Southern Watersnakes typically have 23 strongly keeled midbody scale rows. Ventral counts range from 120-143 (124-141 in NC specimens; Palmer and Braswell, 1995), with 50-89 (65-85) subcaudals and a divided anal plate. Head scale counts are typically: 8 supralabials, 10 infralabials, 1 loreal, 1 preocular, 2-3 postoculars, 2 nasals, and 1+3 temporals. Palmer and Braswell (1995) noted variation in scalation across multiple specimens in NC.

Southern Watersnakes have a maximum recorded total length of 158.8 cm (62.5 inches). Palmer and Braswell (1995) reported a 127.5 cm female specimen from NC. Tail lengths account for approximately 21-30% of total length, though Nerodia often will be found missing portions of their tail. Sexual dimorphism is not pronounced in this species, though females typically reach larger sizes.

Southern Watersnakes do not have enlarged posterior teeth and do not produce venom. However, they will vigorously defend themselves when threatened. They will thrash, bite, musk, and engage in "blocked-flight aggressive behavior" (Means, 2010). Their can be painful, but they are otherwise not dangerous to humans or pets.

Technical Reference: Palmer and Braswell (1995); Ernst and Ernst (2003); Gibbons and Dorcas (2004)

Field Guide Descriptions: Palmer and Braswell (1995); Ernst and Ernst (2003); Gibbons and Dorcas (2004); Beane et al. (2010).

Online Photos: Google iNaturalist GBIF

Observation Methods: Southern Watersnakes are common in and near bodies of water. They can be occasionally encountered crossing roads between habitats.

Distribution in North Carolina

County Map: Clicking on a county returns the records for the species in that county.

Key Habitat Requirements

Habitat: This species occurs in virtually all permanently and semi-permanently waters of the Coastal Plain. These include shallow bays, borrow pits, beaver ponds, sloughs, streams, rivers, swamps, and lakes (Palmer and Braswell, 1995; Beane et al., 2010; Gibbons, 2017).

Biotic Relationships: Southern Watersnakes are generalists that predate a broad array of prey, especially fish and anurans (Gibbons and Dorcas, 2004). Fish consumed include eels (Anguillidae), suckers (Catostomidae), sunfish and bass (Centarchidae, Elassomatidae), shad (Clupeidae), various minnows and shiners (Cyprinidae, Fundulidae, Umbridae), pickerel (Esocidae), catfish (Ictaluridae), perch (Aphredoderidae, Percidae) and mosquitofish (Poeciliidae). Amphibians consumed include larval and aquatic salamanders (including mudpuppies, sirens, newts, and plethodontids) and adult frogs and their tadpoles (including toads, narrowmouth toads, spadefoot toads, tree and chorus frogs, and true frogs). There are also a handful of records of crayfish as prey of these snakes (Ernst and Ernst, 2003; Gibbons and Dorcas, 2004). Some researchers suggest these snakes may undergo an ontogenetic change in diet, from primarily fish as juveniles to primarily frogs as adults (Mushinsky and Lotz, 1980; Muskinsky et al., 1982), though that may vary geographically.

Documented predators of adult Southern Watersnakes include alligators, ophiophagous snakes (cottonmouths and kingsnakes), and herons. Predatory and wading birds (hawks, egrets and herons), snapping turtles, and large fish also likely predate this species (Palmer and Braswell, 1995; Gibbons and Dorcas, 2004).

Life History and Autecology

Breeding and Courtship: Southern Watersnakes reach sexual maturity at body lengths of approximately 50 cm. Mating occurs in the spring and early summer (April to June), but varies with locality.

Reproductive Mode: Southern Watersnakes are viviparous; young are typically born in summer or fall (late June to October) after a gestation period of approximately 80 days. Litters average more than 20 neonates, and large females may birth litters of 50 or more neonates.

Neonates average approximately 22 cm in total length and weigh an average of 5 g.

Aquatic Life History: Southern Watersnakes are semiaquatic and can be found in and around most permanent or semipermanent bodies of freshwater within their range.

Terrestrial Life History: Like the closely related Common Watersnake, individuals may be most active at night, but diurnal activity is also frequently reported, and we have found Southern Watersnakes actively foraging in slow-moving waters or crossing roads during the day. They will frequently cross roads, and will hibernate under debris or in rotting stumps and logs near water. They have been recorded in North Carolina in every month except December; they are most active during spring and summer, and as a result most records are from April to August.

Home range estimates are not known from North Carolina, but in South Carolina, home ranges were estimated to average 3.5 ha (35,000 m²; Minimum Convex Polygons; Camper and Chick, 2010).

General Ecology

Adverse Environmental Impacts

Status in North Carolina

NHP State Rank: S5

Global Rank: G5

Photo Gallery for Nerodia fasciata - Southern Watersnake		13 photos are shown.
	Recorded by: Erich Hofmann and Kayla Weinfurther New Hanover Co. Comment:	Recorded by: C. Teague Beaufort Co. Comment: Photo: C. Teague
	Recorded by: Travis McLain Washington Co. Comment:	Recorded by: Travis McLain Washington Co. Comment:
	Recorded by: Erich Hofmann and Kayla Weinfurther Columbus Co. Comment:	Recorded by: Erich Hofmann and Kayla Weinfurther Columbus Co. Comment:
	Recorded by: Erich Hofmann and Kayla Weinfurther New Hanover Co. Comment:	Recorded by: Erich Hofmann and Kayla Weinfurther Craven Co. Comment:
	Recorded by: Mark Shields Robeson Co. Comment:	Recorded by: Mark Shields Carteret Co. Comment:
	Recorded by: Erich Hofmann and Kayla Weinfurther Craven Co. Comment:	Recorded by: Mark Shields Martin Co. Comment:
	Recorded by: Mark Shields Pender Co. Comment:

Nerodia fasciata - Southern Watersnake

Photo Gallery for Nerodia fasciata - Southern Watersnake

13 photos are shown.