Is the cottonmouth as aggressive as people say?

In 2002, two herpetologists, J. Whitfield Gibbons and Michael Dorcas, put a reputation to the test with a pair of boots and a pair of tongs. They approached free-ranging cottonmouths, stood beside them, stepped on them, and picked them up with tongs shaped like a hand. According to summaries of the paper, none of the snakes bit when a researcher simply stood beside them, and one of 22 bit the boot when stepped on. The headline result was not a rampage.

The snake in that study is the cottonmouth (Agkistrodon piscivorus), a venomous, semiaquatic pit viper of the southeastern United States whose reputation is bigger than its record. People say it chases them, and that it lies in wait to drop into boats. This article uses the cottonmouth to sort out snake myths and mix-ups: aggression, the name “water moccasin,” swimming, and the harmless water snakes that get blamed for all of it.

The cottonmouth is venomous. This article is not a guide to handling venomous snakes, and the best way to meet one is from a distance.

Meet the cottonmouth

The Animal Diversity Web says the cottonmouth ranges from the James River in Virginia to western Missouri, and south to the Florida Keys and western Texas. It prefers wetlands (bays, salt marshes, lakes, creeks, ditches and river bottoms) but also occurs on land under logs and vegetation. The UF/IFAS Extension page says it usually stays within about 30 feet of water. The diet is broad: mainly mammals and fish, plus frogs, turtles, snakes, birds, eggs, insects and carrion. It is a pit viper, like the Western diamondback rattlesnake and the Golden lancehead, which is why the table below lists a facial heat-sensing pit.

Like the Common garter snake, the cottonmouth gives birth to live young. The two litter figures disagree, which is a good reminder that field numbers vary by place and by study.

A field test of the “aggressive” label

Here is what two summaries of the Gibbons and Dorcas paper report. The Louisiana Exotic Animal Resource Network says the study recorded 80 interactions, and that many snakes escaped before the researchers could get close. The Orianne Society’s summary reports consistent percentages. We could not open the paper’s full text, so treat the numbers as reported, not verified.

The Orianne Society says the most common behaviors were gaping, trying to escape and vibrating the tail. A snake that gets picked up by a giant hand has some excuse for being cross. It is a limited test: free-ranging snakes, one study, one region. But it does not look like an animal that attacks on sight.

The white mouth is a warning

The name comes from the white lining of the mouth. The Animal Diversity Web says that before biting, a cottonmouth shakes its tail, makes a rustling noise, raises its head, coils and opens its white mouth, and it can also spray a foul-smelling musk. The Missouri Department of Conservation says that no other snake gapes like this, and that harmless water snakes tend to flatten their heads and necks instead. The UF/IFAS page adds that studies it cites suggest gaping snakes strike more often than those vibrating their tails. A gape is therefore a message, and the polite reading is “back up.”

Swimming, and the water snake problem

The Missouri Department of Conservation says cottonmouths often swim with their heads raised, so their backs stick out above the water. It also says northern water snakes sometimes swim with only the head above the water. Swimming posture is a clue, not a test. The UF/IFAS page adds that cottonmouths hunt fish and can bite underwater. For a snake adapted to life in salt water instead, see the Yellow-bellied sea snake.

Harmless snakes are the main source of confusion. Missouri has seven non-venomous semi-aquatic species, which far outnumber cottonmouths there, and the northern water snake is the one most often mistaken for one.

Several of these traits need a close look, and close looks are a bad idea with venomous animals. Missouri’s wildlife code protects snakes, and the Missouri Department of Conservation says harmless ones are often killed by mistake, so a wrong guess can hurt an animal that did nothing wrong.

One snake, many names

The cottonmouth is also called the water moccasin, lowland moccasin, trapjaw and gapper. “Water moccasin” is simply another name for the same snake. The mix-up starts when people assume that any snake seen in the water is a cottonmouth, which the Missouri Department of Conservation calls false.

Names are shifting among scientists, too. The Reptile Database notes that a 2015 study split the Florida cottonmouth off as its own species, Agkistrodon conanti. The IUCN record we use still lists Agkistrodon piscivorus, and several sources here describe the cottonmouth as one species that includes Florida. Where they differ, we follow the roster name.

Common myths and mix-ups, in one place

Myth: it chases people. The Orianne Society and the UF/IFAS page both say no. A cornered snake may head for cover that happens to be where you are standing.

Myth: it waits to drop into boats. The Louisiana Exotic Animal Resource Network lists this among the unsupported claims.

Myth: it cannot bite underwater. The UF/IFAS page says that is false.

Mix-up: every snake in the water is a cottonmouth. The Missouri Department of Conservation says that is false, and the numbers there favor harmless species.

Mix-up: it lives everywhere. It does not occur north of the Missouri River in Missouri, and the Louisiana Exotic Animal Resource Network notes that people report cottonmouths in states where the snake does not occur.

Mistake: calling it harmless. It is venomous. The UF/IFAS page advises treating every bite as venomous and calling 911.

Conservation status

The cottonmouth is listed as Least Concern on the IUCN Red List of Threatened Species. That is the category as distributed by GBIF, the Global Biodiversity Information Facility, and we checked it on November 9, 2026. Least Concern means the species was evaluated and does not meet the criteria for a threatened or near-threatened category.

The Animal Diversity Web says its populations appear stable and that it has no U.S. federal special status, but it also names humans as the main predator of adults, mostly indirectly through habitat destruction. Our sources do not rank the threats beyond that. The Missouri Department of Conservation adds that harmless snakes are often killed because they are mistaken for cottonmouths, and that the state’s wildlife code protects snakes. We have no confirmed population trend beyond the Animal Diversity Web’s note that populations appear stable.

Categories are reviewed and can change, and the copy GBIF distributes can trail the IUCN website by some months, which is why we print the date we checked. GBIF’s copy does not give the year of the IUCN assessment, so we do not state one.