The swamps, marshes and waterways of Texas are loaded with snakes.

In most cases, every dark-colored snake encountered in these realms is labeled a “water moccasin” or “cottonmouth.” In reality, the vast majority are simply nonvenomous watersnakes or even other species such as the hognose snake.

The water moccasin is the largest species of the genus Agkistrodon. Agkistrodon piscivorus, the water moccasin or cottonmouth, is a pit viper found in the southeastern United States. Adults are large and capable of delivering a painful and potentially fatal bite. When antagonized, they will stand their ground by coiling their bodies and displaying their fangs. Although their aggression has been exaggerated, individuals may bite when feeling threatened or being handled. This is the world’s only semiaquatic viper, usually found in or near water, particularly in slow-moving and shallow lakes, streams, and marshes. The snake is a strong swimmer and will even enter saltwater. It has successfully colonized islands off both the Atlantic and Gulf coasts.

The generic name is derived from the Greek words ancistro (hooked) and odon (tooth), and the specific name comes from the Latin piscis (fish) and voro (to eat); thus, the scientific name translates into “hooked-tooth fish-eater.” The common names water moccasin and cottonmouth refer to the threat display, where this species will often stand its ground and gape at an intruder, exposing the white lining of its mouth.

The broad head is distinct from the neck, and the snout is blunt in profile with the rim of the top of the head extending forward slightly further than the mouth.

Juvenile and subadult specimens generally have a more contrasting color pattern, with dark crossbands on a lighter ground color. The ground color is then tan, brown or reddish brown. The tip of the tail is usually yellowish, becoming greenish yellow or greenish in subadults, and then black in adults. On some juveniles, the banding pattern can also be seen on the tail. 

This species is often confused with the copperhead, Agkistrodon contortrix. The watersnakes of the genus Nerodia are also similar in appearance, being thick-bodied with large heads, but they have round pupils, no loreal pit, a single anal plate, and a distinctive overall color pattern.

The fact is there are only four types of venomous snakes in all of North America. These are cottonmouths, copperheads, rattlesnakes and coral snakes. There are numerous varieties of each, but those are the types. In other words, everything else is nonvenomous.

Included here are a few classic cottonmouth photos along with a few of the mimics out there to help you tell the difference when fishing on your favorite lake or squirrel hunting in that deep, dark creek bottom.

  A true cottonmouth is not a snake to be toyed with. They can deliver a deadly bite of hemotoxic venom that destroys tissue. Unlike their reputation of being super dangerous, most cottonmouths simply prefer to be left alone. If you encounter one giving you the “cottonmouth,” consider yourself lucky. That is a warning before biting.

  The yellowbelly watersnake, pictured here and with me on the previous page, looks a lot like a cottonmouth from the top view. As you can see its belly is yellow and has no pattern, unlike the cottonmouth. These snakes have extreme musking abilities and are usually the “moccasin” most people claim they can smell before seeing.

  The diamondback water snake is the largest water snake in Texas, growing (confirmed) up to six feet long, but they might get even large according to some reports.

These snakes are sometimes called “water rattlers” because of the diamond pattern on their back, but they are nonvenomous and have no rattles. They do, however, have lots of attitude. When cornered they may strike out and flatten their head.

  Hognose snakes can grow up to 2.5 feet long. When they are in the black phase like this one, they look a lot like a cottonmouth. These snakes will puff up their bodies and hiss. They will also flatten their heads out like this one is doing and will strike with their mouth closed and play dead. In fact, they are so adamant about convincing you they are dead, they will turn back over if you turn them right side up.

 The nonvenomous water snakes have round pupils. Cottonmouths such as this one have split pupils. That’s an easy way to tell whether the snake you are looking at is venomous or not. However, we don’t recommend getting that close.

  George Van Horn of Reptile World Serpentarium in Kissimmee, Florida extracts venom from a huge Florida cottonmouth. If you are ever in the Orlando area check his place out. We go every time and always learn something new. You can actually watch his venom extracting presentations, which are truly an amazing thing to see.

  THE University of Florida has a great table describing how to tell the difference between nonvenomous water snakes and cottonmouths. This is a great list of general guidelines. The characteristic I find most helpful is the thick and blocky head of cottonmouths. The other watersnakes have much thinner heads and will flatten them out when cornered.


—story by Chester Moore


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