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Purple shade indicates vouchered specimens. Light blue (cyan) shade indicates photographic records. Yellow shade indicates verified sighting. Slanted hatch indicates pre-1980 records only

NOTE: Not all specimens upon which these maps are based have been verified.

Key Characters: Dark body bands anteriorly, blotches posteriorly; back scales strongly keeled; anal plate divided.

Similar Species: Broad-banded water snake, juvenile plainbelly water snake, cottonmouth, copperhead.

Subspecies: Midland water snake, N. s. pleuralis; northern water snake, N. s. sipedon.

Description: Large (up to 120 cm TL), stout snake with highly variable dorsal coloration. Back light brown, gray, or tan with about 30 reddish brown or dark brown crossbands and blotches (northern subspecies has more than 30, midland subspecies fewer than 30). Crossbands wider on back than on side, and usually wider than intervening paler areas. Belly light yellow with many red or brown half-moons.

Habitat: Streams, lakes, ponds, and ditches. Commonly seen basking on rocks and logs or foraging in the water. Takes shelter under rocks, logs, and other debris along shore.

Natural History: Like most other water snakes, it readily bites and voids feces when handled. Mates in May and gives birth to 20-50 young in late July or August. Newborn are 15-25 cm TL. Diet consists mainly of fish and amphibians. Predators include other snakes and large shore birds. Many are killed by people who mistake them for cottonmouths (even hundreds of miles north of the range of cottonmouths) or copperheads.

Status: Abundant throughout Illinois in both natural and man-made bodies of water.