‹ Compare two snakes
Northern Cottonmouth vs Northern Watersnake
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Melanie Gaddy, no rights reserved
Northern Cottonmouth
Agkistrodon piscivorus
VenomousMartyn Drabik-Hamshare, no rights reserved
Northern Watersnake
Nerodia sipedon
Non-venomousThe quick way to tell
Check the face. The cottonmouth has a vertical pupil and a dark mask through the eye. The watersnake has round pupils and no mask.
Eyes ★ This settles it
Vertical slit pupil; heat-sensing pit between eye and nostril.
Round pupil, eyes set high on the head; no heat-sensing pit.
Head
Blocky, heavy brow, dark mask through each eye, pale snout.
Narrow head barely wider than the neck; flattens when threatened.
Pattern
Dark olive to nearly black, with faint wide bands clearest on young snakes.
Crossbands up front breaking into blotches toward the tail; reddish half-moons on the belly.
Pits
A deep heat-sensing pit on each side of the face, between the eye and the nostril.
None. There is no pit between the eye and the nostril.
Tail
Thick-based; young have a yellow tail tip.
Tapers evenly; no rattle.
What it does
Coils, vibrates its tail and gapes to show a white mouth lining.
Basks on docks and banks; drops into water, bites hard if grabbed.
Where it lives
Southeast from southeastern Virginia through the Carolinas, northern Georgia and Alabama, west to central Texas and Oklahoma, and up the Mississippi valley to southern Illinois, Missouri and southeastern Kansas.
Eastern and central US from Maine and Ontario south to the Carolinas and the Gulf states (just into the Florida panhandle), west to Colorado, Nebraska and Oklahoma; introduced in California.