A Cottonmouth (Agkistrodon piscivorus) in Minnesota, and Historical Reports of Other Pit Vipers Unexpected in the Upper Midwest

The collection of an Agkistrodon piscivorus (Cottonmouth) on a barge in Winona, MN lends credence to the belief that this species may occasionally be carried up the Mississippi River via commercial boat traffic. Consideration is given to reports of other crotaline snakes not expected to occur in the upper Mississippi River drainage, including Agkistrodon contortrix(Copperhead), Crotalus viridis (Prairie Rattlesnake), and Crotalus atrox (Western Diamondback Rattlesnake).