10 Facts About Cottonmouth Bites That Could Matter One Day
The South's water moccasin has a fearsome reputation, and most of it is folklore. Knowing how this snake really behaves, and what to do after a bite, makes you safer than any myth will.
The cottonmouth, also called the water moccasin, is the only venomous snake in North America that spends much of its life in and around water. It is a pit viper, a close relative of the copperhead and a more distant cousin of the rattlesnakes. It lives in swamps, ponds, drainage ditches, rice fields and slow rivers across the Southeast.
Few American animals carry more folklore. People will tell you that cottonmouths chase swimmers, drop into boats on purpose and attack in gangs. None of that is true. What is true is simpler and more useful: this is a heavy, well-camouflaged snake that prefers to be left alone and that defends itself when it is stepped on or grabbed.
Bites are uncommon. Across the whole country, venomous snakes bite roughly seven to eight thousand people a year and kill about five, and cottonmouths account for a small share of those bites, well behind rattlesnakes and copperheads. Even so, every cottonmouth bite is a medical emergency, because the venom destroys tissue and the damage grows with every hour that passes without treatment.
These ten facts are worth knowing if you fish, hunt, paddle, garden or simply live in cottonmouth country. They cover how to recognize the snake, how to avoid a bite, and exactly what to do, and not do, if one happens.
Read all the way to the end. The last fact is the one that prevents most bites.
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Range
1. They live only in the Southeast
Did you know this?Cottonmouths are found from southeastern Virginia south through the Carolinas and Georgia to the tip of Florida, west across the Gulf states to central Texas, and north up the Mississippi valley through Arkansas, western Tennessee and Kentucky, and southern Missouri to the southern tip of Illinois. They also live in eastern Oklahoma. They are snakes of the lowlands and are absent from the higher Appalachians.
AdvertisementBiologists now recognize two species. The northern cottonmouth, Agkistrodon piscivorus, covers most of that range. The Florida cottonmouth, Agkistrodon conanti, lives in peninsular Florida and far southern Georgia. They look alike and their bites are treated the same way, so the difference matters only to specialists.
Within the range they use almost any still or slow water: cypress swamps, beaver ponds, river sloughs, farm ponds, roadside ditches and salt marsh edges. They also travel overland, especially in spring and fall, and can turn up hundreds of yards from the nearest water.
AdvertisementRememberIf you live north of Virginia, in the upper Midwest or anywhere in the West, there are no cottonmouths. The "moccasin" in your pond is a harmless water snake. -
Identity
2. Most "cottonmouths" are something else
Did you know this?Several species of harmless water snake share the same ponds and rivers, and they outnumber cottonmouths in most places. Northern, banded, brown, diamondback and plain-bellied water snakes are all thick-bodied, dark and quick to flatten their heads when frightened, which makes them look more dangerous than they are. They are killed in large numbers every year by people who believe they have found a moccasin.
AdvertisementAn adult cottonmouth is usually two to four feet long and very stout for its length, with a broad, blocky head that is clearly wider than the neck. A dark band runs from the eye back to the corner of the jaw, and the top of the head is flat with a sharp ridge above each eye, which gives the snake a stern, browed look. Old adults are often nearly solid dark olive or black.
AdvertisementBehavior on the water is the most useful clue from a distance. A cottonmouth swims high, with most of its body riding on the surface like a floating stick, and often holds its head tilted upward. Water snakes typically swim with only the head and neck showing and dive readily. On land, a cottonmouth tends to hold its ground and coil, while a water snake bolts for the water.
RememberNo single feature is reliable from every angle, and you should never move closer to check. Treat any thick-bodied snake near Southern water as venomous and give it room.Advertisement -
Warning
3. The white mouth is a signal
Did you know this?A cottonmouth that feels threatened and cannot slip away puts on one of the clearest warning displays of any American snake. It pulls its body into a loose coil, tilts its head back and holds its mouth wide open, showing the bright cotton-white lining. Against a dark body and dark mud, the effect is like a small flag.
The display often comes with other signals. The snake vibrates its tail, which makes a rattling buzz in dry leaves. It flattens its body to look larger. It may also release a strong, musky odor from glands at the base of the tail, a smell some people compare to a billy goat.
AdvertisementAll of this takes energy and exposes the snake, and it exists for one purpose: to end the encounter without a fight. Venom is how a cottonmouth gets its food, and it does not waste it on animals too large to eat if a bluff will do.
The open white mouth is not a threat. It is a snake telling you exactly where it is and asking you to go away.
RememberStop, locate the snake, and back away slowly the way you came. A displaying cottonmouth that is given six feet of space will stay where it is.Advertisement -
Temperament
4. They are not aggressive
Did you know this?The cottonmouth's reputation for attacking people does not survive careful observation. In well-known field research in the Southeast, biologists approached wild cottonmouths, stood beside them, stepped on them gently with a boot and picked them up with a mechanical hand. Most snakes tried to escape. Many gaped and bluffed. Only a minority bit, and those were mostly animals that had been picked up.
AdvertisementStories of cottonmouths "chasing" people have a simple explanation. A frightened snake heads for the nearest water or cover. If you happen to be standing between the snake and its refuge, it will come in your direction. Step aside and it will keep going.
The boat stories are equally innocent. Brown water snakes and other harmless species bask on branches over the water and drop when startled, and now and then one lands in a boat. Cottonmouths climb less and bask mostly on logs, banks and low stumps.
AdvertisementRememberNearly all bites happen when a snake is stepped on, picked up, or cornered by someone trying to kill it. Leaving it alone is the most effective protection there is. -
Young snakes
5. Juveniles look different
Did you know this?Cottonmouths do not lay eggs. Females give birth to live young in late summer, usually in August and September, in litters that commonly number five to ten. The newborns are eight to ten inches long and fully equipped with fangs and venom from the first day.
Young cottonmouths look little like their parents. They are boldly patterned with wide, dark brown crossbands on a lighter tan or reddish background, much like a copperhead. The tail tip is bright sulfur yellow or yellow-green. A young snake lies still and wiggles that tail like a caterpillar to lure frogs and lizards within reach.
AdvertisementThe pattern darkens with age, and the yellow tail fades within the first year or two. Because juveniles are small and colorful, people are more inclined to pick them up or brush them aside with a hand. A juvenile delivers less venom than an adult, but the venom is the same, and a bite to a finger can still cause serious, lasting injury.
RememberA small, banded snake with a yellow tail near Southern water is a young cottonmouth or copperhead. Do not handle it, and keep children and pets away.Advertisement -
Water
6. They can bite underwater
Did you know this?A persistent myth holds that a snake cannot bite underwater because it would drown. Cottonmouths catch much of their food below the surface. Fish, frogs, tadpoles, sirens and even young turtles are seized and held underwater, and the snake's scientific name, piscivorus, means fish eater.
Bites to people in the water do happen, though rarely. They almost always involve a hand or foot placed directly on a snake that is resting under an undercut bank, among roots, beneath a dock or in a submerged brush pile. Hand fishing for catfish, sometimes called noodling, carries this risk, as does feeling around under a boat ramp or reaching for a snagged lure.
AdvertisementA swimming cottonmouth in open water is not hunting you. It is crossing from one place to another and will change course if you give it a clear path.
RememberDo not reach under logs, banks or dock edges with bare hands, and shuffle your feet when wading in murky shallows. -
Venom
7. It damages tissue
Did you know this?Cottonmouth venom is a mixture of enzymes and proteins that break down cell membranes, muscle and the walls of small blood vessels. It is designed to begin digesting prey from the inside. In a person, the result is local destruction around the bite, along with effects on the blood.
AdvertisementThe pain is immediate and severe, often described as burning. Swelling starts within minutes and spreads up the limb over the following hours. Bruising, blood-filled blisters and oozing from the fang marks follow. Many people also feel nauseated, weak and lightheaded, and some notice tingling around the mouth. In serious bites, blood pressure drops and the blood loses some of its ability to clot.
AdvertisementNot every bite injects venom. A meaningful share of pit viper bites, around one in four or five, are "dry." You cannot tell a dry bite from an early envenomation at the scene, because swelling can take an hour or more to declare itself. Every bite needs hospital evaluation.
With modern care, almost no one dies of a cottonmouth bite. The real risk is to the hand or foot that was bitten.
RememberDeaths are rare with treatment, but untreated bites can cause permanent stiffness, scarring or loss of tissue in a finger, hand or foot.Advertisement -
First aid
8. Do less, not more
Did you know this?Correct first aid for a cottonmouth bite is short. Move away from the snake so it cannot bite again. Sit down and stay as calm as you can. Take off rings, watches, bracelets and tight shoes or sleeves on the bitten limb before swelling traps them. Keep the limb still and roughly level with the heart. Then get to an emergency department, by ambulance if possible.
If you have a pen, mark the edge of the swelling on the skin and write the time beside it. That simple line helps the hospital judge how fast the venom is spreading. Wash the wound gently with soap and water if it causes no delay, and cover it loosely with a clean, dry dressing.
AdvertisementEverything else that tradition recommends does harm. Cutting the wound damages tendons and nerves and removes no useful amount of venom. Suction, by mouth or with a commercial extractor, does not work and injures the tissue. Ice worsens tissue damage. A tourniquet or tight band concentrates the venom in one place and can cost a limb. Electric shock is useless and dangerous. Alcohol and caffeine do nothing helpful, and aspirin or ibuprofen can increase bleeding.
AdvertisementRememberNo cutting, no sucking, no ice, no tourniquet, no electric shock, no alcohol. Stillness and a fast trip to the hospital are the whole of first aid. -
Treatment
9. Antivenom works
Did you know this?Hospitals throughout the Southeast treat pit viper bites routinely. Two antivenoms are approved in the United States for cottonmouth envenomation: CroFab and Anavip. Both are made from antibody fragments that bind venom in the bloodstream and tissue and stop the injury from advancing. Neither can reverse damage already done, which is why time matters.
AdvertisementIn the emergency department, staff will check the wound, mark and re-measure the swelling every 15 to 30 minutes, and draw blood to check platelets and clotting. If the swelling is progressing or the blood tests are abnormal, antivenom is given through an IV, and further doses follow until the swelling stops. Pain is treated properly, and your tetanus protection is brought up to date. Antibiotics are not routinely needed.
People with apparent dry bites are watched for at least eight hours before going home. Those who receive antivenom usually stay a day or two. Swelling and stiffness can last for weeks, and the hospital will arrange follow-up blood tests, because clotting problems occasionally return several days later.
AdvertisementRememberCall 911, or Poison Control at 1-800-222-1222 for guidance on the way. Do not try to catch or kill the snake. Doctors treat what they see in the patient, and the same antivenom covers every native pit viper. -
Prevention
10. Most bites are avoidable
Did you know this?Bites cluster in the warm months, from April through October, and on the hands, feet and ankles. That pattern tells you most of what you need to know about prevention: protect your lower legs, and see where you put your hands.
AdvertisementWear closed boots and long pants when walking in marsh, along pond edges or through tall grass near water. Step onto a log and look before stepping over it. Carry a flashlight after dark, because cottonmouths are active on warm nights and often lie on trails, boat ramps and roads. Use a rake or stick, not your hand, to move brush, boards and flood debris. After high water, expect snakes in places they do not usually visit, including porches, sheds and woodpiles.
AdvertisementAround the home, keep grass short near ponds and ditches, store lumber and firewood off the ground, and keep dogs leashed along the water's edge. Never attempt to kill or move a venomous snake yourself. A large share of bites happen during exactly that attempt.
RememberA dead or even decapitated snake can bite by reflex for an hour or more. Never pick one up.
The short version
The cottonmouth is a shy, heavy-bodied pit viper found only in the lowland Southeast. It warns before it bites, it does not chase people, and it is far outnumbered by harmless water snakes that look similar. Give any thick snake near the water six feet of space and a clear way out, and the encounter is over.
If someone is bitten, the plan is brief. Get away from the snake, keep the person calm and still, remove rings and anything tight, hold the limb at about heart level, and call 911 or Poison Control at 1-800-222-1222. Then go to an emergency department, where antivenom and careful monitoring do the real work.
Forget what you have seen in old Westerns. The knife, the suction, the ice and the tourniquet all make a bad situation worse. Calm, stillness and speed are what save hands and feet.
Last updated . This article is for general information and isn't medical advice. In an emergency call 911.
