North Carolina Wildlife Resources Commission

Cottonmouth

Scientific Name:  Agkistrodon piscivorus
Classification:  Nongame (VENOMOUS)
Abundance:  Common (blue)

Species Profile (PDF)

          
Photo: Jeff Hall

     

Also known as the water moccasin, the cottonmouth derives its common name from the white color of the inside of its mouth, which is revealed when the snake gapes to defend itself. Two species of the genus Agkistrodon occur in the United States, the cottonmouth and the copperhead (A. contortrix). Both occur in North Carolina. There are three subspecies of cottonmouth. The subspecies in North Carolina is the Eastern cottonmouth (Agkistrodon piscivorus piscivorus). Along with copperheads and rattlesnakes, the cottonmouth is a member of the viper family (Viperidae). Its venom toxicity ranks fourth of the six species of North Carolina venomous snakes (after the coral snake, eastern diamondback rattlesnake and timber rattlesnake).
The venomous cottonmouth, like all pit vipers, has a facial pit for sensing infrared radiation (heat), but unlike rattlesnakes, it lacks a rattle. The head is distinctly wider than the neck, with a dark bar on both sides from the eye to the angle of the jaw. There are nine large scales on the crown of the head, and the pupils of the eyes are vertically elliptical. The cottonmouth is patterned with dark crossbands invaded by
light olive or brown centers. These dark crossbands are widest on the sides of the animal and narrowest on the top. This is the opposite of most nonvenomous water snakes that may resemble cottonmouths superficially (in water snakes, the dark crossbands have the widest part of the band on the top). Juveniles have bright yellow or greenish tail tips, and the details of the crossband pattern are most evident in this age group. Older individuals are often completely dark and unpatterned.

Adults measure 3 ft.–4 ft. but are known to reach 6 ft. The record is 74 in.

The cottonmouth is the most aquatic of North American venomous snakes and can be found in most habitats associated with water. Like other ectothermic (“cold-blooded”) reptiles, cottonmouths bask on branches, logs or stones at the water’s edge. They are most active at night and become inactive at the onset of cold weather, brumating underground over winter. Common hibernacula are on rocky wooded hillsides, in crayfish burrows, under rotting stumps and in mammal burrows. If approached, some cottonmouths will retreat but others are defensive and will stand their ground. They often coil, vibrate their tail and open their mouth to reveal the white inner lining.

Cottonmouths have a very generalized diet; they eat fish, other snakes, small mammals, birds, lizards, amphibians, turtles, crayfish and insects. Cottonmouths exhibit an onto-genetic shift in foraging strategy, with juveniles ambushing mostly amphibian prey from open sites around the edges of wetlands, while adults employ more active foraging in a variety of habitats.

Like most pit vipers, cottonmouths are viviparous (give birth to living young). Both males and females reach sexual maturity at 2–3 years. Mating takes place in both spring and fall. Females give birth to a litter of 3–14 young between August and October. Females may congregate before giving birth and remain with their broods, possibly to defend them, for several days. Because breeding is energetically expensive, many vipers, including cottonmouths, commonly reproduce in alternating years. Neonates (newborns) are approximately 9.5 in.–10 in. long and are strongly patterned with light-centered dark brown to reddish-brown crossbands. The tip of the tail is yellow and is used as a lure to attract prey.

Learn more by reading the cottonmouth species profile.

The cottonmouth is classified as a nongame species and has no open season. It is unlawful for any person to take, or have in possession, any nongame mammal or bird unless that person has a collection license or is collecting fewer than 5 reptiles or fewer than 25 amphibians that are not endangered, threatened, or special concerned species.

The cottonmouth is venomous. Many people fear snakes and worry for the safety of people and pets when snakes are present. In reality, snakes are shy creatures that pose little to no threat to us when left alone. Snakes are an important part of our environment, keeping populations of pests such as rodents, slugs, and insects in check. Plus, snakes are a food resource to other animals such as foxes, raccoons, bears, eagles, hawks, and owls. 

When someone encounters a snake, usually the person and the snake are both caught off guard. The best plan is to leave the snake alone and give it plenty of space. In most cases, given time, the snake will move out of the area on its own. Like all reptiles, snakes are cold-blooded, meaning that their internal temperatures follow that of the ambient temperatures where they are found. On a cool day, a  snake encountered basking may not yet have the energy to move away from you, so it may require more time and warmer temperatures before it can retreat. 

The Wildlife Commission does NOT send people out to trap and remove snakes. The best plan for citizens of North Carolina is to learn about snakes and alter habits to minimize negative interactions, and in the process, learn to coexist with snakes.

Snakes can be difficult to monitor and survey, as most of them possess great camouflaged patterns and remain hidden within certain habitats.  One way biologists monitor corn snakes is through the use of artificial cover materials such as plywood boards, roofing tin, concrete blocks, and other materials. Plywood tends to be better at attracting smaller snake species, while larger snakes are more often found under tin.  Snakes will seek out these artificial shelters for thermoregulation and as a result, this method is particularly successful during spring and fall.