Nerodia

Nerodia is a genus of nonvenomous colubrid snakes commonly referred to as water snakes due to their aquatic behavior. The genus includes nine species, all native to North America.

Nerodia
Nerodia rhombifer, diamondback water snake
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Colubridae
Subfamily: Natricinae
Genus: Nerodia
Baird & Girard, 1853

Description

Nerodia species vary greatly, but all are relatively heavy-bodied snakes, sometimes growing to 1.2 m (4 feet) or longer in total length. They have flattened heads, with small eyes that have round pupils, and keeled dorsal scales. Species like N. fasciata display distinct banding, whereas other species, like N. erythrogaster, have blotching, and those like N. rhombifer have diamond-shaped patterning. Most species are brown or olive green, or some combination thereof with markings being brown, or black. Yellow or cream-colored accenting is common.

Behavior

Water snakes, as their name implies, are largely aquatic. They spend the vast majority of their time in or very near permanent sources of water. Often they can be found basking on tree branches which overhang slow-moving streams or ponds.

Diet

Their primary diet is fish and amphibians, and they are quite adept at catching both in their aquatic environment. They will also consume small reptiles and rodents that live near water.

Defense

While their initial instinct is to flee when disturbed, water snakes will readily defend themselves if they are unable to escape. They do not often hesitate to strike or bite if handled, and will often expel a foul-smelling musk from their cloacae.

Reproduction
Nerodia rhombifer, diamondback water snake, giving birth

Nerodia species are viviparous, breeding in the spring and giving birth in the late summer or early fall. They are capable of having 90 or more young, but broods generally are much smaller. Neonates are around 20–26 centimetres (8–10 in) in length.

Species and subspecies

The following species and subspecies are recognized as valid:[1]

Nerodia erythrogaster transversa, blotched water snake
  • Nerodia fasciata (Linnaeus, 1766) – banded water snake
    • Nerodia fasciata confluens (Blanchard, 1923)
    • Nerodia fasciata fasciata (Linnaeus, 1766)
    • Nerodia fasciata pictiventris (Cope, 1895)
  • Nerodia floridana (Goff, 1936) - Florida Green watersnake
  • Nerodia harteri (Trapido, 1941) – Brazos water snake
  • Nerodia paucimaculata (Tinkle & Conant, 1961) – Concho water snake
  • Nerodia rhombifer (Hallowell, 1852) – diamondback water snake
    • Nerodia rhombifer blanchardi (Clay, 1938)
    • Nerodia rhombifer rhombifer (Hallowell, 1852)
    • Nerodia rhombifer werleri (Conant, 1953)
  • Nerodia sipedon (Linnaeus, 1758) – common water snake
    • Nerodia sipedon insularum (Conant & Clay, 1937)
    • Nerodia sipedon pleuralis (Cope, 1892)
    • Nerodia sipedon sipedon (Linnaeus, 1758)
    • Nerodia sipedon williamengelsi (Conant & Lazell, 1973)
  • Nerodia taxispilota (Holbrook, 1842) – brown water snake

Distribution

Nerodia species are widely spread throughout the southern and eastern half of the United States, north into Canada and south into Mexico, as well as to the island of Cuba. Many ranges overlap, and intergrading of subspecies is not unknown, but is rare.

In captivity

Due to how widespread and extremely common they are in the wild, water snakes are often found in the exotic pet trade, throughout the United States, though they are rarely captive bred. Their relative physical unattractiveness, compared to other available pet snake species, and their poor disposition make them less than attractive pets. They are easy to care for though, and do quite well in captivity.

Conservation concerns

Some species, such as N. harteri and N. paucimaculata are only found in very isolated localities and are protected by state laws, but the majority of Nerodia species hold no specific conservation status. Due to their habitat choice, poor disposition, and vague similarity to the venomous cottonmouth (Agkistrodon piscivorus), they are frequently mistaken for them. This results in many more water snakes being killed every year than cottonmouths. Often, water snakes found in areas where the cottonmouth does not range are still killed by humans out of ignorance and fear.

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References
  1. ITIS (Integrated Taxonomic Information System). www.itis.gov.
  • "Nerodia". Integrated Taxonomic Information System. Retrieved 12 May 2006.
  • Northern Water Snake Species account from the Iowa Reptile and Amphibian Field Guide
  • Diamondback Watersnake - Nerodia rhombifer Species account from the Iowa Reptile and Amphibian Field Guide

Further reading
  • Baird, S.F., and C.F. Girard. 1853. Catalogue of North American Reptiles in the Museum of the Smithsonian Institution. Part I.—Serpents. Smithsonian Institution. Washington, District of Columbia. xvi + 172 pp. (Genus Nerodia, p. 38.)
  • Clay, W.M. 1938. A Synopsis of the North American Water Snakes of the Genus Natrix. Copeia 1938 (4): 173-182.
  • Conant, R. 1975. A Field Guide to Reptiles and Amphibians of Eastern and Central North America, Second Edition. Houghton Mifflin. Boston. xviii + 429 pp. ISBN 0-395-19977-8 (paperback). (Genus Natrix, p. 139.)
  • 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. xiii + 365 pp. (Genus Natrix, pp. 205–206.)
  • 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) (Genus Natrix, p. 467.)
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