The water moccasin, commonly referred to as a cottonmouth, is a venomous snake that lives in the southern portion of the United States. The venom is highly toxic and can be lethal, so a bite should be treated as soon as possible with CroFab antivenom. (According to wildlife ecologist Dr. David Steen, in contrast to their reputation, cottonmouths are not aggressive; rather, they are defensive, so if you see one, keep your distance and do not do anything that could seem threatening to the snake. If you are bitten, remain calm and proceed to the nearest emergency room, calling in advance. It is important to stay as still as possible and keep the bitten area below the level of the heart; if you are with friends, have them carry you to their vehicle. Do not bind, tourniquet, or try to suck the venom from the bite.) Water moccasins are classified as a pit vipers. The water moccasin, which lives near water and is an excellent swimmer, can be identified in a number of ways so that the observer can tell this creature apart from the many species of water snakes that also dwell where it resides.
Realize that the water moccasin will not be found in northern parts of the United States. The cottonmouth's range is from southern Virginia and south through the Carolinas, Georgia, Florida and then westward into Alabama, Mississippi, Louisiana and portions of eastern Texas. It can be found as far north as Missouri, Oklahoma and southern sections of the state of Illinois. If you are in a state such as Connecticut or Minnesota, you will not encounter a cottonmouth.
Recognize that a water moccasin can be as long as 6 feet in extreme cases and has a much larger girth than most snakes. The water snakes for which it is often confused are slimmer, even if they happen to be as long. The colors of water moccasins vary from region to region and subspecies to subspecies, with some having dark brown bands against a darker body and others being nearly all black.
Watch a water moccasin when it is swimming to tell it apart from other water snakes. When in the water, a water moccasin will have most of its body above the surface, as the snake has the pit viper characteristic of being buoyant. Typical water snakes swim with the majority of their body beneath the water's surface. The moccasin inhabits ponds, edges of lakes, swamps, bayous and other bodies of water.
Identify the water moccasin by its behavior when threatened. If you happen to stumble upon a normal non-venomous water snake, it will rapidly flee from you. However, if a water moccasin feels that it does not have an obvious escape route, it will gladly stand and put up a fight. This is when it will employ its coiling and open-mouthed tactics. When a cottonmouth feels threatened, it will coil up and open its mouth wide, revealing the white lining of its mouth from which it gets its common name. If you see this, you can be certain that it is a cottonmouth. Its mouth will normally face straight up when in this posture.
If you are identifying a dead snake, you can look more closely at the snake's characteristics. Look for the telltale characteristics of all pit vipers. Cottonmouths have a pit that exists between the eye and nostril which is used to detect its prey, as it is heat-sensitive. The water moccasin's head will be triangular in shape, thick, and obviously wider than its neck. The eyes will not be visible when observed from above, the pupils will be oval rather than round, and the tail will be short rather than long.
Stay clear of any snake you suspect is a cottonmouth, as its venomous bite is potentially fatal and always very painful.