Nerodia sipedon - Northern Watersnake
From 12 - 42 inches (30 - 107 cm) up to 55 inches in length (140 cm).
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 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.
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.
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.
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.
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.
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.
It is against the law to capture, move, possess, collect, or distribute this invasive species in California.
See: California Department of Fish and Game Restricted Species Regulations