Cottonmouth
Agkistrodon piscivorus
Also called: water moccasin, northern cottonmouth
A thick-bodied, semi-aquatic pit viper of southern swamps, sloughs, and slow rivers, often confused with the many harmless water snakes that share its habitat.
- Kind
- Venomous
- Typical length
- 2 to 4 feet
- Range
- The southeastern U.S. from Virginia to Florida and west to eastern Texas, and north along the Mississippi River
- Regions
- Southeast, Midwest & Plains
- Habitat
- Water & wetlands
- When active
- Warm months, day and night
Note: Cottonmouth bites need emergency care. Be careful around wet logs, stumps, and banks, and never reach where you cannot see.
How to identify it
- The body is thick and heavy, dark olive, brown, or nearly black, and may be faintly banded.
- The head is blocky with a dark band through the eye and a pale upper lip.
- At rest it often coils and may open its mouth wide, showing a pale lining.
- It swims with its body riding high on the water, while many harmless water snakes swim lower.
Often confused with
- Northern Water Snake: the most common lookalike; it is slimmer, with a narrower head, and lacks the dark eye band.
If you meet one
- Stop and look before you step. Check where your feet and hands will land, especially near logs, rocks, and brush.
- Back away slowly and give the snake plenty of room, at least several body lengths. It wants to leave, not fight.
- Do not try to kill, catch, move, or photograph it up close. Most bites happen to people doing exactly that, and a dead snake can still bite by reflex.
If someone is bitten
- Move away from the snake and call 911 right away.
- Keep the person calm and as still as possible. Take off rings, watches, and tight clothing near the bite before swelling starts.
- Keep the bitten area still and about level with the heart, and get the person to a hospital. Antivenom is the treatment.
- Do not cut the bite, suck out venom, use a tourniquet, apply ice, or give alcohol. These make things worse.
- In the U.S., Poison Help (1-800-222-1222) can advise while you wait for help. Do not wait to see whether symptoms develop.
Field notes
Cottonmouths hunt fish, frogs, and small animals in or near water. Because harmless water snakes look so similar and are far more common, the safest approach is to leave every water snake alone.
Related guides
This page is a general reference, not medical advice and not a substitute for identifying a real snake with an expert. Many snakes are protected by state law, and rules about killing or handling them vary, so check your state wildlife agency; our state resources directory links to each one. For any bite, get emergency care.