‹ Compare two snakes
Northern Cottonmouth vs Brown Watersnake
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Melanie Gaddy, no rights reserved
Northern Cottonmouth
Agkistrodon piscivorus
Venomous(c) Leila Dasher, some rights reserved (CC BY)
Brown Watersnake
Nerodia taxispilota
Non-venomousThe quick way to tell
Check the face. The cottonmouth has a vertical pupil, a dark eye mask and a pale snout. The Brown Watersnake has round pupils and square, checkerboard blotches.
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.
Head clearly wider than the neck, but no eye mask and no pale snout.
Pattern
Dark olive to nearly black, with faint wide bands clearest on young snakes.
Big squarish blotches alternating with side blotches - a checkerboard, not bands.
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, no markings.
What it does
Coils, vibrates its tail and gapes to show a white mouth lining.
Drops from branches into the water and swims away.
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.
Southeast coastal plain and Piedmont: southeastern Virginia through all of Florida, west into Alabama.