Southern Watersnake

The banded water snake or southern water snake (''Nerodia fasciata'') is a species of mostly aquatic, nonvenomous, colubrid snakes endemic to the Midwest and Southeastern United States.

Geographic range

''N. fasciata'' is natively found from Indiana, south to Louisiana, and east to Florida.

In 1992, its congener ''Nerodia sipedon'' (northern or common water snake) and it were found in three sites in California by the US Fish and Wildlife Service (USFWS). In 2009, more than 300 banded water snakes were caught in suburbs of Los Angeles by the Nerodia Working Group of USFWS. Then in May 2016, the species was found in the Colorado River basin near Yuma, Arizona. Further trapping did indeed catch large numbers of them, indicating that a thriving invasive population exists in that area.

Description

Adults of the banded water snake measure from in total length, with a record size (in the Florida subspecies) of in total length. In one study, the average body mass of adult banded water snakes was .

It is typically gray, greenish-gray, or brown in color, with dark crossbanding. Many specimens are so dark in color that their patterning is barely discernible. The ventrum (belly) is typically an off-white to white. They have flat heads, and are fairly heavy-bodied. Banded water snakes may also be identified by a dark stripe which extends from the eye to the angle of the jaw. If irritated, they release a foul-smelling musk to deter predators. This species also exhibits sexual dimorphism in which the female is generally longer and heavier than the male.

Their appearance leads them to be frequently mistaken for other snakes with which they share a habitat, including the venomous cottonmouth.

Habitat

''N. fasciata'' inhabits most freshwater environments such as lakes, marshes, ponds, and streams. Conant, R. 1975. ''A Field Guide to Reptiles and Amphibians of Eastern and Central North America, Second Edition.'' Houghton Mifflin. Boston. xviii + 429 pp. (paperback). (''Natrix fasciata fasciata'', p. 146 + Plate 20 + Map 100.) Banded water snakes are active both day and night and may be seen basking on logs or branches overhanging the water or foraging in shallow water. They will typically stay within emergent vegetation along the shoreline or in the shallow littoral zone of their habitat.

Diet

The species preys mainly on fish and frogs. Juveniles mainly consume fish and shift towards eating frogs as adults. This shift may be caused by large frogs being mechanically too difficult for juveniles to consume (which may suggest juveniles may be unable to open their jaws wide enough for adult frogs), because large frogs are energetically too costly for juveniles to catch, or because juveniles are at risk if swallowing prey requires a long time.

Using its vomeronasal organ, also called Jacobson's organ, the snake can detect parvalbumins in the cutaneous mucus of its prey.

Reproduction

The species is viviparous, giving birth to live young. The brood size varies from 15 to 20 young born in late July or August. Newborns are 200–240 mm (about 8.0–9.5 in) in total length. Wright, A.H., and A.A. Wright. 1957. ''Handbook of Snakes of the United States and Canada.'' Comstock. Ithaca and London. 1,105 pp. (in 2 volumes) (''Natrix sipedon fasciata'', pp. 525–529, Figure 156.) The banded water snake is able to hybridize with the common watersnake, although this is not frequent. Physical characteristics are insufficient to distinguish such hybrids, and DNA analysis is required.

Subspecies

The three recognized subspecies of ''N. fasciata'', including the nominotypical subspecies, are:
*''N. f. confluens'' (Blanchard, 1923) - Broad-banded water snake - Oklahoma, Arkansas, Louisiana, Mississippi, Missouri, East Texas.
*''N. f. fasciata'' ( Linnaeus, 1766) - East Texas, Louisiana, southeastern Oklahoma, Arkansas, western Mississippi, southern Alabama, Florida, southern Georgia, South Carolina, North Carolina, southeast Missouri and Illinois.
*'' N. f. pictiventris'' ( Cope, 1895) – Florida banded water snake - Florida, southeast Georgia. Introduced to Brownsville, Texas and California.

Taxonomy

Some sources consider '' N. clarkii compressicauda'' and ''N. clarkii taeniata'' to be subspecies of ''N. fasciata''. Also, some sources have considered ''Nerodia fasciata'' to be a subspecies of ''Nerodia sipedon''.Schmidt, K.P., and D.D. Davis. 1941. ''Field Book of Snakes of the United States and Canada.'' G.P. Putnam's Sons. New York. 365 pp. (''Natrix sipedon fasciata'', pp. 221–222, Figure 72. + Plate 24, Center, on p. 344.)

References

Other sources

Herps of Texas: ''Nerodia fasciata''

External links

*
California Nerodia Watch – iNaturalist

Further reading

* Linnaeus, C. 1766. ''Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, diferentiis, synonymis, locis. Tomus I. Editio Duodecima, Reformata.'' L. Salvius. Stockholm. 532 pp. (''Coluber fasciatus'', p. 378.)

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Nerodia
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Extant Pleistocene first appearances
Reptiles described in 1766
Taxa named by Carl Linnaeus
Reptiles of the United States
Fauna of the Southeastern United States