CaliforniaHerps.com

A Guide to the Amphibians
and Reptiles of California


Northern Watersnake - Nerodia sipedon

(Linnaeus, 1758)
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Northern Watersnake California Range MapLocation of introduced population
in California: Red

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observation link



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Introduced: not native to California

It is against the law to capture, move, possess, collect, or distribute this invasive species in California.

If you find an aquatic snake in California that you think is a Watersnake (Nerodia), please send pictures
of it to the California Nerodia Site, which is tracking the distribution of this potential threat to native fish and wildlife.


Northern Watersnake Northern Watersnake Northern Watersnake
Adult, Placer County. Adult, Placer County. Adult, Placer County, with juvenile bullfrog in background
Northern Watersnake Northern Watersnake Northern Watersnake
  Adult, Placer County.  
Northern Watersnake Northern Watersnake Northern Watersnake
  Adult, Placer County.  
Northern Watersnake Northern Watersnake Northern Watersnake
Adult, Placer County. © Richard Porter
Northern Watersnake Northern Watersnake Northern Watersnake
Juvenile, Placer County. © Richard Porter
Northern Watersnake Northern Watersnake  
Adult, Placer County © Sabrina Howe

 
Northern Watersnakes From Their Native Habitat
Northern Watersnake Northern Watersnake Northern Watersnake
Juvenile, Lumpkin County, Georgia
Adult, Fairfax County, Virginia Adult, Fairfax County, Virginia
Northern Watersnake Northern Watersnake Northern Watersnake
Adult, Anne Arundel County, Maryland Adult, Anne Arundel County, Maryland Adult, Fairfax County, Virginia
     
Habitat in California
Northern Watersnake CA Habitat Northern Watersnake CA Habitat Northern Watersnake CA Habitat
Habitat, Placer County Habitat, Placer County Habitat, Placer County © Sabrina Howe
  Northern Watersnake CA Habitat  
  Habitat, Placer County © Sabrina Howe

 
Short Videos
Northern Watersnake Northern Watersnake  
A large adult Northern Watersnake in Placer County crawls into the water. A large adult Northern Watersnake in Placer County in the water.  
Description
Not Dangerous to Humans
Size
From 12 - 42 inches (30 - 107 cm) up to 55 inches in length (140 cm).
Appearance
Dorsal and ventral patterns are variable. Color can be brown, gray, brownish-black, or reddish, darkening with age. Older adults are often all dark in color without any markings. The head is typically one color and is gradually more rounded and more flat on top than the head of Nerodia fasciata.

The body is usually marked with dark blotches and dark crossbands ring the neck. The dorsal crossbands on the rear of the snake change to "alternating middorsal and lateral blotches usually at or before midbody." *

The underside is white, yellow, or gray with crescent or half-moon-shaped markings that are dark and sometimes tan or yellowish in the center. Spots may be in a double row or in a striped pattern.
Behavior and Natural History
Little is known of the natural history of this snake in California. In its natural habitat, they are active both day and night, and are usually seen in the morning or late afternoon when they are basking in sunny areas on stumps, rocks, logs, or vegetation next to water. Activity takes place from April to October in the northern part of its range, and earlier in the spring and later in the fall in the southern range. They hibernate during winter in burrows, crevices, or rock piles near or close to water, sometimes in den shared with other snake species.

This snake will bite and release excrement and musk when threatened or picked up. The saliva contains an anticoagulant which creates profuse bleeding in the victims of its bite.
Diet
Diet consists of small aqatic vertebrates such as fish, frogs, salamanders, small mammals, and even small birds, and invertebrates such as various kinds of worms, leeches, and crayfish. Snakes typically hunt for food along the edge of shallow water.

A captured Roseville snake regurgitated a non-native American Bullfrog and a native Pacific Chorus Frog (Sierran Treefrog), confirming that these introduced snakes are a threat to native wildlife. (Oliver J. Miano, Jonathan P. Rose, and Brian d. Todd, Herpetological Review 43(2), 2012)
Reproduction
In the natural range of this snake, mating occurs from April to June. Females typically give birth to 15 - 30 live young between August and October in the northern part of its range and in July or August in the southern part of its range. Breeding may not occur every year.
Range
This species is found throughout most of the United States east of the Mississippi River excluding parts of Maine, most of Florida and parts of the southeast coast, and west of the Mississippi through the central part of the country west into Colorado. Also occurs north of the Great Lakes into part of southeast Canada.

In California they have been established in Roseville, Placer County (Balfour et al. 2007. Herpetol. Rev. 38:489).
Habitat
This snake lives just about anywhere near fresh water - rivers, creeks, canals, lakes, ponds, oxbows, reservoirs, bogs swamps and marshes. It also inhabits brackish and saltwater habitats in some locations.

In Placer County, they have been found along the edge of a large freshwater marsh.
Taxonomic Notes
There are four subspecies of Nerodia sipedon in the United States:

N. s. insularum
- Lake Erie Watersnake
N. s. pleuralis - Midland Watersnake
N. s. sipedon - Common Watersnake
N. s. williamengelsi - Carolina Watersnake

It is not known which subspecies has become established in California.
Conservation Issues  (Conservation Status)
Spread of this snake downstream into the Sacramento Valley could possibly threaten populations of the already endangered Giant Gartersnake, Thamnophis gigas. It could also pose a threat to other native fish and wildlife.

As of Janurary 2008 it is against the law to capture, move, possess, collect, import, or distribute this invasive species and all non-native water snakes of the genus Nerodia in California without a permit: California Department of Fish and Game (Sec. 671, Title 14, Calif. Code of Regulations).
See: California Department of Fish and Game Restricted Species Regulations
Taxonomy
Family Colubridae Colubrids Oppel, 1811
Genus Nerodia American Watersnakes Baird and Girard, 1853
Species


sipedon Northern Watersnake (Linnaeus, 1758)
Original Description
sipedon, Nerodia Serpentes
Nerodia sipedon (Linnaeus, 1758) - Syst. Nat., 10th ed., Vol. 1, p. 219

from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz

Meaning of the Scientific Name
Nerodia - Greek - nereis - name of sea nymph
sipedon - Greek - sepedon - rottenness, decay; a serpent whose bite causes mortification

from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz

Alternate Names
None

Related or Similar California Herps
Thamnophis sirtalis fitchi - Valley Gartersnake
Thamnophis gigas - Giant Gartersnake
Nerodia fasciata pictiventris - Florida Water Snake

More Information and References

California Nerodia - a website about introduced populations of Nerodia found in California.

California Department of Fish and Wildlife

* Gibbons, J. Whitfield, Michael E. Dorcas. North American Watersnakes - A Natural History. University of Oklahoma Press. 2004.

Conant, Roger, & Collins, Joseph T. A Field Guide to Reptiles and Amphibians Eastern and Central North America Third Edition. Houghton Mifflin Company, 1998.

Bartlett, R.D., & Alan Tennant. Snakes of North America - Eastern and Central Regions. Gulf Publishing Co., 2000.
Conservation Status

The following status listings come from the Special Animals List and the Endangered and Threatened Animals List which are published by the California Department of Fish and Wildlife.


It is against the law to capture, move, possess, collect, or distribute this invasive species.
See: California Department of Fish and Game Restricted Species Regulations


Organization
Status Listing
U.S. Endangered Species Act (ESA) None
California Endangered Species Act (CESA) None
California Department of Fish and Wildlife None
Bureau of Land Management None
USDA Forest Service None


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