Water Moccasin vs. Cottonmouth: Know Your Snakes!

  • By reComparison Contributor
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Difference between Water Moccasin and Cottonmouth

For most people who live in the southern United States, the Water Moccasin and the Cottonmouth are familiar and unique animals, with the latter often thought of as being slightly more poisonous than the former. We know now that these are two names for what operate as essentially the same creature, and that they are both deadly poisonous. It is easy to see why the two are often thought of as being different however, which is why we thought it fitting to reveal more about these fascinating snakes.

Physical Characteristics

The Water Moccasin or Cottonmouth is quite a large snake, and its muscular body can measure anywhere from 30 to 48 inches. The variety often referred to as Cottonmouth is actually closely related to the Copperhead Viper or Highland Moccasin which grows from 24 to 36 inches and it is quite easy to recognize given its triangular head and distinctive elliptical pupils. The body of the snake is typically colored brown with olive and black markings often present. Although the belly of the snake is a bit lighter in color, the same stripes and markings that can be seen on top go across the belly as well. The name Cottonmouth actually stems from the fact that white markings that look like a patch of cotton can be seen around the area of the throat.


Both people who are familiar with the Water Moccasin and the Copperhead know that they coil up tightly and open their mouth in preparation for a strike. Regardless of what name it goes by, this is quite an aggressive snake to be sure, and it displays many of the same characteristics as highly territorial animals, including mammals. In fact, unlike most snakes that would retreat at an intruder, the Cottonmouth/Water Moccasin has been known to defend its territory aggressively and even advance toward intruders!

Precautions And Treatment

Both the Water Moccasin and the Copperhead are highly venomous snakes, and they should be provided with the respect that they deserve. If you happen to chance upon one in the water, keep in mind that it is perfectly in its element, while you aren't. In such cases, it would be best to leave the immediate vicinity as quickly as you can without rousing the ire of the snake by making movements that it may construe as threatening. If in the unfortunate event that you are bitten, it is important to seek medical treatment as soon as possible. Keep in mind that snakebites from these varieties cause as many as 12 deaths each year, so it is essential to take such bites very seriously.


Water Moccasin

  • A large snake coming in at 30 to 48 inches
  • Is perfectly in its element in water
  • Is highly venomous


  • Also quite a large and heavy snake
  • Has a distinctive cotton looking white patch near its throat, hence the name
  • Is very quite aggressive and highly venomous
  • Along with the Water Moccasin is responsible for up to 12 deaths a year

Which snake is more dangerous?
  • Water Moccasin
  • Cottonmouth

Discuss It: comments 11

  • Guest
  • frankie wrote on December 2011

What's the difference between the two smakes

A water moccassin is a cottonmouth.

  • Guest
  • rqueen wrote on June 2015

They are very similar but I have handled both of them and when you have them together you can see the difference. Some people also consider the Copperhead snake to be just like them, but again they are not the same.

No. No. No... Cottonmouths and water moccasins are the SAME species of snake. There are visual differences among individual snakes within the species... Juveniles are lighter pigmented, and their crossband patterns are more pronounced, wheras adults become darker, and may even appear to be a uniform black or dark brown color, both adult and juvenile present with a white or cream ventral coloration.

Copperheads are in the same genus, but are an entirely different species with totally different biological and physiological traits.

  • Guest
  • kenneth wrote on April 2014

I didn't think the plain water moccasins were poisionous just the cotton mouths,

  • Guest
  • rqueen wrote on June 2015

They are both VERY poisonous. Here is a way to tell the difference if you ever run into one:

Water Moccasin

A large snake coming in at 30 to 48 inches

Is perfectly in its element in water

Is highly venomous


Also quite a large and heavy snake

Has a distinctive cotton looking white patch near its throat, hence the


Is very quite aggressive and highly venomous

Along with the Water Moccasin is responsible for up to 12 deaths a year

.... This is actually all so wrong, I don't even know where to begin...

I'll just pick one thing...

Snakes are not POISONOUS. Snakes are VENOMOUS.

Poisons are ingested, or absorbed; venoms are injected (via bites or stings).

Monarch Butterflies are poisonous, because they contain toxins that are harmful if ingested.

Snakes are venomous, because they inject toxin into their prey via biting.

From the title onward, this whole thread is just wrong.

(Shakes head)

They are the same snake. A water moccasin or cottonmouth is highly dangerous as well as the copperhead. They are pit vipers. Basically any snake in water is dangerous and you should avoid it. Copperheads, water moccasins and coral snakes all like water so any snake in water needs to be avoided at all costs.

This is untrue. Cottonmouths are semiaquatic. Copperheads and rattlesnake species prefer to remain dry. Other than the word "coral" in their common name, coral snakes are not aquatic, and prefer dry habitats. Coral snakes are not even vipers, they're the only elapid found in the Americas, which is why they have also gained the moniker "the american cobra."

While one may not relish sharing a swimming area with snakes, the thought process "all water snakes pose danger to us, so we should fear and avoid them," is absolutely wrong. Other than the cottonmouth (Agkistrodon piscivorus), the only other semiaquatic snakes that share a habitat are harmless, and are often killed out of mistaken identity.

Respect nature, but do not fear it, and get your biology straight before you start accusing harmless animals of being deadly.


  • Guest
  • Bob Reeves wrote on May 2015

I am no snake expert, but I believe the Cottonmouth is a flat blackish/brownish color with a white mouth, while the Water Moccasin is a shiny blackish/brownish color and has a more pinkish mouth. Either way, they are both deadly and have bad attitudes!

I believe the title for this should be "cottonmouth vs. copperhead." Water moccasin is another name for cottonmouth, they are the same snake, Agkistrodon piscivorus; the common name varies, but there is only one species of cottonmouth. The copperhead is Agkistrodon contortrix, and sometimes referred to as the "highland moccasin." This is an entirely different species, but they belong to the same genus, Agkistrodon. There is one other species in this genus, Agkistrodon bilineatus, the Mexican Viper, or Mexican Moccasin. All three of these distinct, yet related species belong to the family Viperidae (vipers), and specifically, the sub-family Crotalinae (pit vipers).

Common names create confusion, this is why in biology, we must rely on the dichotomy of scientific names to avoid confusion.

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