Squamata suborder Serpentes
Nerodia cyclopion -- Mississippi Green Watersnake
All information found on this site falls under the INHS's Internet License Agreement.
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: Subocular scale between eye and supralabial scales; dark belly covered with pale half-moons; back scales strongly keeled; anal plate divided.
Similar Species: Diamondback water snake, cottonmouth.
Description: Large (up to 100 cm TL), stout snake with greenish black or olive brown back and sides. Fifty barely visible, narrow black crossbands above vague alternating dark blotches. Belly dark brown or black with off-white half-moons. No other water snake in Illinois has the subocular scale.
Habitat: Quiet backwater sloughs and cypress-tupelo swamps of extreme southwestern counties.
Natural History: This viviparous snake mates in May and gives birth to 10-20 young in late July or August. Newborn are 25-27 cm TL. Diet mainly of fish, but also includes amphibians. Predators include other snakes and large shore birds. Water snakes are often killed by people who mistake them for cottonmouths.
Status: Threatened in Illinois. Threats include drainage of sloughs and swamps and removal of aquatic vegetation.