Reptiles of North Carolina

Scientific Name:	Common Name:		Family (Alpha):

NC Records
Colubridae Members:
Nerodia taxispilota - Brown Watersnake

Photo: K. Sanford, K. Haben

Photo: Mark Shields

Taxonomy

Class: Reptilia

Order: Serpentes

Family: Colubridae

Subfamily: Natricinae

Other Common Name(s): Brown 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 taxispilota, the Brown Watersnake, is one of four Nerodia in North Carolina. This species is restricted to the southeastern United States, from southern Virginia to southern Florida, and west to southern Alabama. In North Carolina, the species ranges down the Coastal Plain to the central Piedmont, and is known from a few scattered records from the western Piedmont. No subspecies are recognized. The generic epithet Nerodia is derived from the Greek neros, "flowing" or "liquid", and dia, "through". The specific epithet taxispilota is derived from the Greek taxis, "arrangement", and spilos, "spot". Taxonomic References: McCranie (1983).

Identification

Description: Brown Watersnakes are large, heavy-bodied snakes with large heads distinct from the neck, sometimes appearing "swollen". Adult dorsal color is brown with prominent dark brown middorsal squares or rectangles and alternating dark brown lateral blotches. The venter is white to yellow, and heavily mottled with black or dark brown markings. Juveniles may be lighter dorsally than adults.

Morphological Features: Brown Watersnakes typically have 29-33 strongly keeled midbody scale rows, reducing to 21-25 posteriorly. Ventral counts range from 128-152 (130-140 in NC specimens; Palmer and Braswell, 1995), with 59-87 (68-87) subcaudals and a divided anal plate. Head scale counts are somewhat variable: 7-11 supralabials, 9-14 infralabials, 1 loreal, 1 preocular, 2-3 postoculars, 2 nasals, and 2-3+2-3 temporals. Palmer and Braswell (1995) noted variation in scalation across multiple specimens in NC.

Brown Watersnakes reach the largest size of any Nerodia in North Carolina, and have a maximum recorded total length of 176.6 cm (69.5 inches). Palmer and Braswell (1995) reported a 152.8 cm female specimen from NC. Tail lengths account for approximately 24-28% of total length, though Nerodia often will be found missing portions of their tail. Females reach larger sizes than males; males have longer, thicker tails and more subcaudals.

Brown 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 autotomize parts of their tail. Their bites are strong and 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: Brown Watersnakes may be found during the day, almost always in or basking above 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 primarily around the edges of large rivers, swamps, and lakes in the Coastal Plain, especially those with wooded shorelines (Palmer and Braswell, 1995).

Biotic Relationships: Brown Watersnakes are primarily fish specialists, with the majority of those prey items being catfish (Ictaluridae). Various sunfish and bass (Centarchidae), shiners (Cyprinidae), pickerel (Esocidae), and perch (Percidae) are also consumed (Camp et al., 1980; Ernst and Ernst, 2003; Gibbons and Dorcas, 2004). Other prey item reported include frogs, crayfish, and small reptiles, though Gibbons and Dorcas (2004) suggested these may have been secondarily ingested prey.

There are few reported first-hand records of Brown Watersnake predation. Alligators are known predators (Brimley, 1909; Mills, in Gibbons and Dorcas, 2004), and large wading birds including herons and egrets have been recorded stabbing at Brown Watersnakes captured in mesh minnow traps (Howell and Harman, 2021). Brimley (1909) reported a cormorant regurgitating part of one near Lake Ellis (Craven Co.). It is likely that various wading birds and ophiophagous snakes (cottonmouths) predate adults, and that juveniles fall prey to those predators and possibly large fish. White et al. (1982) suggested that attacks by snapping turtles (Chelydra serpentina) are a probable cause for tail injuries in many Brown Watersnakes.

Life History and Autecology

Breeding and Courtship: Male Brown Watersnakes reach sexual maturity at snout-to-vent lengths of approximately 53 cm, while females are larger, typically 72 cm (Ernst and Ernst, 2003). Mating occurs in the spring (April to May), but in other parts of its range may extend from early February.

Reproductive Mode: Brown Watersnakes are viviparous; young are typically born in September. Litters average 28 neonates, and large females produce larger litters.

Neonates average approximately 27–29 cm in total length and weigh an average of 11 g.

Aquatic Life History: Brown Watersnakes are aquatic and can be found in swamps, lakes, and marshes, and are common in larger bodies of water, including brackish tidal marshes. They will use submerged logs or man-made structures (such as piers and duck blinds) as cover.

Terrestrial Life History: Brown Watersnakes are primarily diurnal, though occasionally active at night, and spend a substantial amount of time basking on limbs and vegetation overhanging water. They are thought to overwinter in cavities along the edges of water. Brown Watersnakes have been recorded in North Carolina February–December; they are most active during spring and summer, and as a result most records are from April to June.

Home range estimates are not known for this species, though Mills et al. (1995) reported individuals moved more than 10 m/day and larger individuals would disperse across rivers.

General Ecology

Adverse Environmental Impacts

Status in North Carolina

NHP State Rank: S5

Global Rank: G5

Photo Gallery for Nerodia taxispilota - Brown Watersnake		7 photos are shown.
	Recorded by: K. Sanford, K. Haben Gates 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 Columbus Co. Comment:
	Recorded by: Erich Hofmann and Kayla Weinfurther Craven Co. Comment: Juvenile	Recorded by: Mark Shields Lenoir Co. Comment:
	Recorded by: Mark Shields Pender Co. Comment:

Nerodia taxispilota - Brown Watersnake

Photo Gallery for Nerodia taxispilota - Brown Watersnake

7 photos are shown.