Northern Cottonmouth vs. Common Watersnake

Both are heavy dark snakes of southern Illinois water. Look at the head from the side: the Cottonmouth has a broad, blocky head much wider than its neck (a watersnake's head is narrow), a dark band running through the eye, edged above by a pale line, a vertical pupil and a pit between the eye and the nostril; the Common Watersnake has a plain-sided head, a round pupil and no pit. A Cottonmouth swims with its body on top of the water and, when cornered, gapes to show the white lining of its mouth. Old Cottonmouths turn nearly plain; Common Watersnakes keep their bands and blotches for life.

Photographs via iNaturalist under Creative Commons licences; the photographers are credited on the sheet.

More comparisons

• Northern Cottonmouth vs. Plain-bellied Watersnake
• Northern Cottonmouth vs. Diamondback Watersnake
• Northern Cottonmouth vs. Mississippi Green Watersnake
• Northern Cottonmouth vs. Eastern Copperhead
• Banded Watersnake vs. Northern Cottonmouth
• Broad-banded Copperhead vs. Northern Cottonmouth
• Brown Watersnake vs. Northern Cottonmouth
• Florida Cottonmouth vs. Northern Cottonmouth
• Florida Green Watersnake vs. Northern Cottonmouth
• Eastern Copperhead vs. Common Watersnake
• Common Watersnake vs. Diamondback Watersnake
• Common Watersnake vs. Plain-bellied Watersnake
• Kirtland's Snake vs. Common Watersnake
• Queensnake vs. Common Watersnake
• Mississippi Green Watersnake vs. Common Watersnake
• Graham's Crawfish Snake vs. Common Watersnake
• Banded Watersnake vs. Common Watersnake
• Broad-banded Copperhead vs. Common Watersnake
• Glossy Swampsnake vs. Common Watersnake
• Brown Watersnake vs. Common Watersnake

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