Tell them apart
Northern Cottonmouth vs. Brown Watersnake
It matters: the Northern Cottonmouth is venomous, while the Brown Watersnake is harmless.
Northern Cottonmouth
Agkistrodon piscivorus
Venomous
- Family
- Viperidae
- Group
- Cottonmouth
- Size
- Usually 2–4 ft, heavy-bodied.
- Identify
- Heavy body, triangular head, vertical pupils, and a heat-sensing pit between each eye and nostril.
Brown Watersnake
Nerodia taxispilota
Harmless
- Family
- Colubridae
- Group
- Watersnake
- Size
- Heavy-bodied, 2–4.5 ft.
- Identify
- Heavy banded or blotched body, round pupils, and a narrow head — unlike the cottonmouth's broad, blocky head.
How to tell them apart
Harmless watersnakes are constantly mistaken for the venomous cottonmouth. Watersnakes have round heads and round pupils and flee into the water.
Never rely on a single feature to judge a live snake. If you cannot positively identify it, keep your distance. Informational only.