The Cottonmouth, also known as the Water Moccasin, is the subject of a whole slew of myths and legends, most of them not true.
The Agkistrodon genus of snakes is exclusively North American, found in the eastern part of the continent from southern Massachusetts to Costa Rica. Biologically, they are pit vipers–heavy-bodied snakes with venom glands, long folding fangs, and heat-sensitive pits on their cheeks which they use to locate prey. They can be best thought of as rattlesnakes (to which they are closely related) without rattles.
There are three species in the Agkistrodon genus: the Cantil, Agkistrodon bilineatus, is found in Mexico and Central America; the Copperhead, Agkistrodon contortrix, is found from the northern US to northern Mexico; and the Cottonmouth or Water Moccasin, Agkistrodon piscivorus, (both common names refer to the same snake) is found from Virginia to Florida. Each of these has a variety of geographic subspecies. There are three subspecies of Cottonmouth: our Florida version is Agkistrodon piscivorus conanti. The Florida Cottonmouth ranges throughout the state, extending in the north over the border into Georgia and Alabama.
Like most pit vipers, the Florida Cottonmouth is big, fat, and lazy. Their adult size averages around 3-4 feet (the record length is just over 6 feet), but they are very heavy-bodied and can weigh as much as five pounds. Young Cottonmouths are brightly colored with red, brown and orange bands across their body and, for the first few months, a bright yellow tail tip (used as a lure to attract frogs or small mammals into striking range). As they get older, they become darker in color. In the northern varieties, the adults tend to be plain olive-brown or black; the Florida subspecies often retains at least some of its juvenile pattern into adulthood. The most visible characteristic is the mahogany-colored bandit’s mask at the side of the face, and the bright white interior of the mouth which is displayed at interlopers as a warning (hence the name “Cottonmouth”).
The pit vipers do not lay eggs to reproduce, but are live-bearers, giving birth to a dozen or so live young, about as long as a pencil and fully venomous, in the spring.
Unlike the other pit vipers, which like dry upland habitats, the Cottonmouths are mostly aquatic (hence the name “Water Moccasin”); they are usually found near freshwater ponds or streams, but will also inhabit brackish inlets. Cottonmouths usually prefer to hunt at night; their most common prey is fish, but they will also take frogs, small alligators, mice and rats, and any other small animal that happens by–including smaller snakes. They will also scavenge dead fish or small aquatic animals. During the day Cottonmouths like to snooze in the sun on shore, which can get them into trouble with domestic pets or humans.
The venom is mostly hemotoxic, and acts by breaking down body tissues and causing internal hemorrhage and shock. It works as a “pre-digestive”. Since Florida Cottonmouths are fairly common and often live in ditches or retention ponds near people, they account for more venomous snakebites in the state than any other species. Although the venom is quite potent, human deaths are rare even without treatment, and with the development of effective anti-venoms, a bite, while causing a lot of local tissue damage, is not dangerous to life. When they feel threatened, Cottonmouths don’t run away like most snakes: instead they will boldly turn to face their attacker, coil up in preparation to strike, and attempt to warn the intruder away by gaping the mouth widely to show the white lining inside. If the attacker doesn’t back down, Cottonmouths are one of the few snakes in the world that will actively advance upon you with the express intention of poking holes somewhere in your body.
Because of this, they have developed a fearsome reputation and are the subject of many myths, most of which are not true. Some of these are:
“Cottonmouths will chase you”. No, they won’t; they don’t crawl around looking for humans to bite, and if you leave them alone, they are happy to leave you alone too. But they are very defensive, and if they feel threatened by you they will actively defend themselves. They don’t bite anybody who doesn’t have it coming, and most bites are the result of somebody doing something dumb like trying to catch or tease the snake.
“Cottonmouths can’t bite underwater”. Sure they can–they eat fish.
“Cottonmouths hide in trees”. This myth results from confusing the Cottonmouth with the much-more-common but similar-looking Water Snakes, who often bask in tree branches, especially those that overhang water so they can drop in and swim away if approached. Cottonmouths, on the other hand, are big and fat, and while they can bask on low branches or rocks, they are not really climbers.
“I saw a Cottonmouth in Pennsylvania/New York/Ohio/South Dakota.” Because of their superficial similarity to Water Snakes, many people assume that any large dark snake they see near water anywhere in the US is a “Water Moccasin”. Real Cottonmouths are found from Florida north to lower Virginia and west to southern Missouri and eastern Texas. Any snake outside of that geographic area is not a Cottonmouth. The most useful way to tell a Cottonmouth from a harmless Water Snake is by behavior: Water Snakes retreat quickly to water when they are threatened, while Cottonmouths often stand their ground and show a willingness to fight. Any snake that does not run away from you, probably has a good reason to be confident, and you don’t want to mess with it.
“Cottonmouths live in big nests.” Cottonmouths are mostly solitary and live alone, and don’t make nests, nor do the mothers care for their young. This myth probably results from the fact that Cottonmouths (and Copperheads and Rattlesnakes) often all hibernate together through the winter in suitable dens, emerging en masse in spring to disperse.
Ecologically, the Florida Cottonmouth tolerates human presence reasonably well (though humans don’t tolerate the snakes and usually kill any that venture out into the open), and it seems to be holding its own. The snakes are important parts of the food web–as mid-level predators they feed on smaller animals, and are themselves fed on by skunks, raccoons, large water birds, adult alligators, and birds of prey.
There are a handful of people who are breeding the Florida Cottonmouth in captivity (an albino form is available) for venomous snake collectors. The snakes are popular with keepers because of their colors and their tendency to calm down in captivity and become relatively docile.