isolated localities and are protected by state laws, but the majority of Nerodia species hold no specific conservation status. Due to their habitat choice, defensive 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. References 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. (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.) External links Animal Diversity Web: Nerodia sipedon Water Snakes - diet, life-cycle, habitats and sub-species Extant Miocene first appearances Taxa named by Spencer Fullerton Baird Taxa named by Charles Frédéric Girard Snake genera