Cottonmouth vs Banded Water Snake

The quick tellBoth have dark crossbands. A banded water snake has round pupils and no heat pit and swims with only its head up. A cottonmouth floats high in the water with a dark band through the eye.

Photo: kirk gardner, CC BY 4.0, via iNaturalist

Cottonmouth

Dangerous · Agkistrodon piscivorus

Heavy, dark olive to black body; bands fade with age
Broad flat head with a dark stripe through the eye
Swims with the whole body high on the water
Opens its mouth wide to show the white lining when threatened

Size: 30–48 in. Habitat: Swamps, slow rivers, marshes and ditches of the Southeast.

A bite is a medical emergency. Most snakes people call water moccasins outside its range are harmless water snakes.

Photo: Brady Reed, CC0, via Wikimedia Commons

Banded water snake

Harmless · Nerodia fasciata

Dark crossbands along the whole body
Dark stripe from eye to jaw angle
Round pupils, no heat pit

Size: 24–42 in. Habitat: Coastal plain wetlands of the Southeast.

Not venomous, though often mistaken for a cottonmouth.

Where each one lives

Cottonmouth only
Banded water snake only
Both
Neither

Cottonmouth: 15 states. Banded water snake: 14 states. Both live in 12 states.

Side by side

	Cottonmouth	Banded water snake
Danger	Dangerous	Harmless
Size	30–48 in	24–42 in
States	15	14
Habitat	Swamps, slow rivers, marshes and ditches of the Southeast	Coastal plain wetlands of the Southeast

Questions

How can you tell a cottonmouth from a banded water snake?

Both have dark crossbands. A banded water snake has round pupils and no heat pit and swims with only its head up. A cottonmouth floats high in the water with a dark band through the eye.

Which one is dangerous?

The cottonmouth: dangerous. The banded water snake: harmless. If you are not sure, keep your distance and do not handle it.

Where do both live?

Both live in 12 states: Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, Missouri, North Carolina, Oklahoma, South Carolina, Tennessee and Texas.