Water Moccasins vs. Cottonmouth Snakes: Are They Different Snakes?

Written by Kristin Hitchcock
Published: June 29, 2023
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Contrary to popular belief, water moccasins and cottonmouth snakes are the same snakes.

Both terms refer to the same species, Agkistrodon piscivorus, a venomous water snake in North America. Read on to learn more about cottonmouth snakes, also known as water moccasins, including how to identify them and where they are located.

Characteristics of Water Moccasins and Cottonmouths

Agkistrodon piscivorus, commonly called the cottonmouth snake, is a species of pit viper native to the southeastern United States. This snake attains an average size of about 31.5 inches long, including the tail. However, some subspecies and specimens can grow over 71 inches long, and some can weigh as much as 10 pounds.

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Thanks to their large venom glands, cottonmouth snakes have large jowls along their thick, muscular bodies, which average 2 to 4 feet long. Their large, triangular heads are a distinctive feature and are even more prominent by the snake’s narrower neck.

The thin neck is another distinct feature because many snake species have no distinctive necks. Water moccasins have vertical, “cat-eye” pupils, and dark stripes extend near each nostril. The snout is pale in comparison with the rest of the head.

Another feature that distinguishes the water moccasin lends it its other common name – cottonmouth. That’s because the inside of the snake’s mouth is bright white, like cotton.

When this snake feels threatened, it pulls itself into a distinctive S-like shape, rearing up and opening its mouth widely. The bright, white interior of the mouth stands in stark contrast to the rest of the snake, serving as a distraction and warning sign. Indeed, you could say that the water moccasin “waves a white flag” when feeling threatened.

The snake’s body is thick and muscular but not exceptionally long, so it is relatively stout in appearance. Its body features scales with distinctive keels, or ridges, along them.


Cottonmouths may vary from black or dark brown to olive or even yellow. Some specimens have banded brown colorations. Cottonmouth snakes’ bellies are paler than their backs.

Juvenile and young adult water moccasins tend to be lighter brown in color, and distinctive bands extend across their bodies. These bands and other patterns fade or disappear entirely as they age.

Therefore, if you see a cottonmouth with distinctive patterning, it is probably reasonably young. Additionally, the tips of juvenile water moccasins’ tails are bright yellow, and the snakes use them as lures by waving them slowly back and forth.

Distinguishing Water Moccasins and Cottonmouths from Non-Venomous Snakes

Florida cottonmouth

Cottonmouths have a triangular head with a shape similar to an arrowhead.


People often mistake harmless snakes for cottonmouths, and this causes the needless death of many non-venomous snakes yearly. The Northern water snake, Nerodia sipedon, is a common victim of this phenomenon. Although it looks like a cottonmouth, the crossbands along its back don’t widen at the ends like the northern water snake’s.

If you live in a place with water moccasins, it helps to know how to distinguish them from non-venomous snakes. Some ways to tell them apart include:

  • Swimming Style – Unlike the brown water snake, Nerodia taxispilota – another snake commonly mistaken for a water moccasin – the cottonmouth snake’s whole body stays at the top of the water while swimming. Other water snakes, including the brown water snake, keep most of their bodies below the water while in motion, and only their heads show when not moving.
  • Pupils – Non-venomous water snakes have round pupils. On the other hand, water moccasins and other venomous water snakes have vertical pupils that look similar to a cat’s.
  • Head Shape – Cottonmouth snakes have triangular heads, while non-venomous snakes are more slender and elliptical. A word of caution: When threatened, non-poisonous water snakes flatten their heads, making them look more triangular.
  • Facial PitsPit vipers, like water moccasins, have facial pits between their eyes and nostrils. Non-venomous water snakes lack these pits, so this is an easy way to tell them apart.
  • Scales – Water moccasins have a single row of scales after the anal plate, while non-venomous water snakes have a double row.


Water moccasins, or cottonmouths, live across much of the southeastern United States. Their range extends from southern Virginia across Florida to eastern Texas. These pit vipers preferred habitats include marshes, swamps, and drainage ditches. You can also commonly spot them on the edges of streams, lakes, and ponds.

When on land, cottonmouth snakes stay close to the water, and you can often find them in open fields. Because of their cold-blooded nature, like all snakes, this species spends much time basking in the sun along the water’s edge on logs, branches, and stones.

Habits of Cottonmouths and Water Moccasins

Water Moccasin, cottonmouth, Agkistrodon piscivorus

Cottonmouth snakes prefer to spend time in wet areas, like ponds and marshlands.

©Rafael R Sandoval/Shutterstock.com

Cottonmouth snakes are often believed to be highly aggressive, but they rarely attack humans. However, at the same time, these snakes will stand their ground if they detect a threat. They also don’t automatically flee at the first sign of trouble.

The water moccasin’s most distinctive defensive feature is opening its mouth wide to display the bright, white interior of its mouth. This flash of white is a warning signal, alerting prey that the snake will not back down, giving it a chance to run away.

Other defensive moves include flattening the body, which helps it to hide and evade detection, and emitting a strong, pungent anal secretion that warns away would-be predators. In this way, these snakes are a bit like skunks.

These water snakes keep their bodies along the surface while swimming but keep their heads sticking out. This can be an excellent way to identify them because many non-poisonous water snakes keep their bodies mostly submerged while swimming.

They are active throughout the year in most areas but may become inactive at the onset of cold weather. Under such circumstances, cottonmouths will brumate until the weather warms up again, seeking out logs and holes in the ground for protection. They can be active by day and night, but they tend to hunt after dark. That’s especially true during the summer months.


In terms of diet, water moccasins are large, muscular ambush predators so that they can prey upon various creatures. These carnivores’ diets primarily consist of fish and frogs. However, they also consume other snakes, turtles, squirrels, rabbits, mice, rats, land snails, birds and their eggs, lizards, and even baby alligators.

They may occasionally consume caterpillars, cicadas, and other insects too. Cottonmouth snakes may also eat smaller cottonmouths in an act of cannibalism.


Water moccasins generally mate in the spring. Both sexes reach sexual maturity at around 2 to 3 years of age. When looking to mate, males slither near females, waving their tails to lure them away from competitors. Male cottonmouth snakes often fight each other for the attention of female snakes, so displays of aggression are not uncommon during the mating season.

The cottonmouth snake is ovoviviparous, which means it incubates its eggs inside its body. Every two to three years, females give birth to live young after a gestation period of three to four months. The average litter size includes 10 to 20 baby snakes born with bright, distinctive colors.

Water moccasins provide no parental care, so newborn snakes slither off to start life on their own immediately.

Classification and Taxonomy

Florida cottonmouth

Cottonmouth snakes belong to the pit viper family, which means that have heat-seeking pits on their heads.

©Ryan M. Bolton/Shutterstock.com

Agkistrodon piscivorus, also known as the water moccasin or cottonmouth snake, belongs to Reptilia, the order Squamata, the family Viperidae and the genus Agkistrodon. It is one of eight species of pit vipers belonging to that genus.

Regarding etymology, Agkistrodon derives from the Greek word ancistro, meaning “hooked,” and odon, meaning “tooth.” The term piscivorus derives from the Latin word piscis, meaning “fish,” and voro, meaning “to eat.”

Therefore, the cottonmouth’s scientific name’s rough translation is “hooked-tooth fish eater.” Of course, this snake has retractable teeth, but the overall shape of the jaw and teeth is fairly hooked. Since water moccasins are water snakes, their diets include many fish.

Therefore, it makes sense to refer to these snakes as fish eaters. However, their diets are more varied than that and include frogs, rodents, and even small alligators.

In addition to water moccasin and cottonmouth, common names for this species include gaper, mangrove rattler, black moccasin, swamp lion, snap jaw, trap-jaw, water mamba, water pilot, and stub-tail snake. Different areas of the country may refer to this snake by different names.

The nickname “gaper” refers to the way in which the snake opens its mouth when threatened. It stretches it open as widely as possible, producing a gaping effect that reveals the white interior.

“Mangrove rattler” makes sense in that these snakes often inhabit mangroves; however, they are not rattlesnakes. Although they shake their tails like rattlesnakes, they don’t have rattles; therefore, they don’t produce any noise.

There are three water moccasin subspecies:

  • Florida Cottonmouth – Known by the scientific name Agkistrodon piscivorus conanti, the Florida Cottonmouth is named after famed herpetologist Roger Conant. This subspecies, also known as the green-tailed moccasin, is found in extreme southern Georgia and throughout Florida, including the Everglades.
  • Western Cottonmouth – This subspecies, A. p. leucostoma, is the smallest of the bunch, with an average length of 27.5 inches. It is typically dark gray or brown in color and has little to no markings. Its range extends from southern Alabama across the Gulf Coast and continues into southeast and central Texas, Oklahoma, Missouri, Illinois, Indiana, southeastern Nebraska, and western Kentucky.
  • Eastern Cottonmouth – Found mostly in southeast Virginia, A. p. piscivorus, the eastern cottonmouth, averages between 20 and 48 inches in length. It is also found along the Atlantic coastal plain, the Piedmont of the Carolinas, and Georgia. This subspecies is found along riverbanks, peninsulas, and coastal islands.


Cottonmouth Snake Showing its Cotton Mouth

Cottonmouths prefer to flee and hide, not fight.

©iStock.com/Gerald DeBoer

Cottonmouth snakes have aggressive reputations, but that is an unfair stereotype. In reality, these snakes hardly ever bite or attack humans. They generally slip away quietly to avoid confrontation if they notice humans in the area.

When confronted by predators, however, they are more likely to stand their ground than to flee. When threatened, the water moccasin will pull itself up into a dramatic S-shaped configuration. It opens its mouth very widely, exposing the bright white interior of its mouth. The white color is reminiscent of cotton, so the snake has the name cottonmouth in many parts of the country.

Ironically, its range is primarily the southern US, where cotton was once king. More than likely, the term “cottonmouth” had at least a little to do with the preponderance of cotton across this part of the country and the crop’s cultural significance.

Male cottonmouths tend to become aggressive during mating season, and they often fight other males to get attention from females. As ambush predators, they prefer sneaking up on potential prey before striking. The element of surprise helps them to take on larger animals, including baby alligators.

Water moccasins use the pits on their faces to detect even minute changes in heat. This allows them to hone in on the precise location of prey, making it easier to strike accurately. These poisonous snakes have retractable fangs and store venom in large glands that form jowls below their heads.


The cottonmouth snake is the only venomous water snake in North America. Although it rarely bites humans, this semiaquatic snake will attack quickly when threatened.

It possesses a powerful cytotoxic venom stronger and more severe than that of the copperhead snake, so it is rightfully feared by people who live in areas where it is found. However, this snake’s venom is less dangerous or toxic than the rattlesnake’s.

When the cottonmouth strikes, it bites on and clamps down tightly. From there, they inject venom into their victim. This snake’s potent venom mainly consists of hemotoxins, which break down blood cells.

Therefore, when this venom enters a victim’s system, it prevents blood from clotting or coagulating like it usually does. As a result, if a water moccasin bites you, you may experience hemorrhaging within your body wherever your circulatory system spreads the venom.

A bite by a cottonmouth is rarely fatal. However, it can cause severe damage and is a medical emergency. Water moccasin venom can cause temporary or permanent muscle damage.

Sometimes, people lose an extremity because of the damage the venom causes. For example, the tissue within a hand or foot may become so starved for oxygenation through the blood that it becomes seriously damaged. If you don’t address the situation quickly enough, amputation may be necessary.

Internal bleeding is another serious potential side effect of being bitten by a water moccasin. Since it’s not usually readily apparent, seeking medical care is essential even if everything seems okay. Victims of water moccasin bites also experience extreme pain in the bite area.

People residing in parts of the country where cottonmouths are common should also protect their pets from these snakes. Dogs and cats may accidentally run across a cottonmouth in the wild and be attacked. Smaller animals are more likely to come to serious harm from the venom, and they can actually die from such snake bites.

Cottonmouth, Water Moccasin – One and the Same

Are water moccasins poisonous or dangerous

Water moccasins are the same as cottonmouth snakes.

©Joe Farah/Shutterstock.com

With its many different nicknames, Agkistrodon piscivorus is often confused with other snakes. Although many people believe that water moccasins are distinct from cottonmouth snakes, the truth is that they are one and the same.

Regardless of what it’s called, all subspecies of this snake are venomous but not particularly aggressive. Before killing a snake, you think is a cottonmouth, try to confirm that it’s not a different water snake species.

Further, since cottonmouths prefer to flee rather than fight, it’s often unnecessary to do anything other than stand aside and wait. By understanding the differences between cottonmouths and non-venomous water snakes, you can avoid causing unnecessary harm to these creatures, so be sure to study up before venturing into areas where they may be encountered.

While humans are certainly predators of cottonmouth snakes, some other predators feed on them. For instance, water creatures like bigmouth bass fish, otters, and snapping turtles commonly eat them. Some birds of prey, like herons, owls, and hawks, will also attack and kill them. And cottonmouths should beware of kingsnakes, who are immune to their deadly venom.

If You Are Bitten by a Cottonmouth or Water Moccasin

If you are bitten by a cottonmouth/water moccasin, call 911 immediately – as it is important to receive antivenom as soon as possible. While waiting for help, try to get away from the area where the snake is located to prevent a second bite.

Remove clothing or jewelry from the area near the bite before swelling occurs. Remain calm and position yourself so the bite is below heart level. Lastly, clean the bite if you can, and cover the bite with a clean dressing. Do not use a tourniquet or ice.

The photo featured at the top of this post is © KF2017/Shutterstock.com

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About the Author

Kristin is a writer at A-Z Animals primarily covering dogs, cats, fish, and other pets. She has been an animal writer for seven years, writing for top publications on everything from chinchilla cancer to the rise of designer dogs. She currently lives in Tennessee with her cat, dogs, and two children. When she isn't writing about pets, she enjoys hiking and crocheting.

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