Cottonmouth - Omnivore of the Wetlands

Sunday, June 15, 2008

Nature Notes
by Bob Thomas

Everyone fears the dreaded cottonmouth (Agkistrodon piscivorus), a seemingly ubiquitous venomous snake. Many people use the terms "cottonmouth" and "water moccasin" as synonyms, while others use the latter to designate non-venomous water snakes. Since these may be dangerous animals, it is best to communicate clearly - call them cottonmouths.

Cottonmouths do not require water to live. They spend more time out of the water (sitting on a log, coiled on a bank, or lying on a limb) than in it, but they hang out in wetlands because that is where most of their preferred food lives. Unlike many snakes that have a rather restricted diet, cottonmouths will eat almost anything. This might sound odd, but it has given them the versatility needed to be quite successful under virtually all conditions they encounter. They are known to eat fish, turtles, birds, eggs, mammals, frogs, tadpoles, carrion of all types, lizards, salamanders, and other snakes, including other cottonmouths. During a drought some years back, biologists were monitoring faunal changes in a swamp near Lafayette. As the water disappeared, species dependent on it vanished, either following the receding water or dying. When the swamp was completely dry, the only snakes to be found were cottonmouths. They were content to function as terrestrial vipers and were found to be feeding primarily on mice and other cottonmouths. When the rains returned, they expanded their diets.

Cottonmouths, as do other pit vipers, give live birth. They don't have a placenta; the young are simply retained inside, each enclosed in a membrane, until they are born. As they leave the mother's cloaca, the young are fully armed with fangs and venom. Although the adults are dark with some evidence of a pattern when they are wet, the young are orange-brown with hour-glass markings somewhat similar to those of copperheads. Their tails are yellow-tipped and they are known to wave them about as bait in order to attract a meal.

The typical defensive posture is to tilt the head up, open the mouth, and erect the fangs. The mouth interior is whitish, hence the name cottonmouth.

Cottonmouths account for the largest number of venomous snake bites in Louisiana due to their abundance and proximity to sportsman and people living in wetlands. Though only rarely fatal with medical treatment, cottonmouth bites are particularly nasty in that compartmentalization (functionally similar to gangrene) may follow. Always go to a hospital when bitten by a venomous or even possibly venomous snake.

Also published in Delta Journal, The Times Picayune, August 2, 1989.

                                 

Adult cottonmouth- about three feet long.                              Subadult cottonmouth - about 18 inches
Typical threat display. long.                                                   Note the vivid pattern visible in
Photo by Bob Thomas.                                                      younger animals and those that are wet.
                                                                                            Photo by James Beck.


                                

Cottonmouth threat display: 1) flashing                                Juvenile cottonmouth. Note the lighter
of fangs in "white" mouth and 2) flattening                           coloration and the yellow-tipped tail.
of the body to appear larger.                                                Photo by Bob Thomas.
Photo by James Beck.