The Water moccasin is a venomous snake, a species of pit viper native to the southeastern United States. As an adult, it is large and capable of delivering a painful and potentially fatal bite. Water moccasins are almost or even totally black, (with the exception of the head and facial markings), the color pattern may consist of a brown, gray, tan, yellowish-olive, or blackish ground color, which is overlaid with a series of 10-17 dark brown to almost black crossbands. The underside of the head is generally whitish, cream, or tan.
Water moccasins are found in the eastern US from the Great Dismal Swamp in southeast Virginia, south through the Florida peninsula and west to Arkansas, eastern and southern Oklahoma, and western and southern Georgia (excluding Lake Lanier and Lake Allatoona). Their range also includes the Ohio River Valley as far north as southern Indiana, and they inhabit many barrier islands off the coasts of the states where they are found. These snakes are usually associated with bodies of water, such as creeks, streams, marshes, swamps, and the shores of ponds and lakes. They are also found in brackish-water habitats and are sometimes seen swimming in saltwater. Water moccasins are not limited to aquatic habitats. In various locations, these snakes are well-adapted to less moist environments, such as palmetto thickets, pine-palmetto forest, pine woods in East Texas, pine flatwoods in Florida, eastern deciduous dune forest, dune and beach areas, riparian forest, and prairies.
Water moccasins are solitary creatures. They may be active during the day and at night. However, on bright, sunny days, they are usually found coiled or stretched out somewhere in the shade. In the morning and on cool days, they can often be seen basking in the sunlight. They often emerge at sunset to warm themselves on the warm ground (i.e., sidewalks, roads) and then become very active throughout the night, when they are usually found swimming or crawling. Contrary to popular belief, they are capable of biting while underwater. In the north, Water moccasins hibernate during the winter. In the southern parts of their range, hibernation may be short or omitted altogether. For hibernation, these snakes use rocky wooded hillsides, burrows of crayfish, tortoises or other mammals, under rotting stumps or other covers. When stressed or threatened, Water moccasins perform a characteristic threat display that includes vibrating their tail and throwing their head back with their mouth open to display the startling white interior; they will often make a loud hiss while the neck and front part of the body are pulled into an S-shaped position. Many of their common names, including "cottonmouth" and "gaper", refer to this behavior. The habit of Water moccasins to snap their jaws shut when anything touches their mouth has earned them the name "trap jaw" in some areas. Other defensive responses can include flattening the body and emitting a strong, pungent secretion from the anal glands located at the base of the tail.
Water moccasins are carnivores and their diet includes mammals, birds, amphibians, fish, frogs, snakes, small turtles, and small alligators. On occasion, juveniles feed on invertebrates. These snakes are opportunistic feeders and sometimes eat carrion, making them one of the few snakes to do so.
It is suggested that Water moccasins are monogamous; this means that during the breeding season a male mates with only one female. Mating occurs in April-May and the young are usually born in August or September. During the mating season, males perform a combat dance and also compete for access to females. Water moccasins are ovoviviparous, with females giving birth to 1-16 live young and possibly as many as 20. However, litters of 6 to 8 are the most common. The gestation period lasts around 4-5 months. Neonates are 22-35 cm in length (excluding runts) and independent at birth. If weather conditions are favorable and food is readily available, growth is rapid and females may reproduce at less than 3 years of age and a total length of as little as 60 cm.
There are no major threats to Water moccasins at present. However, they suffer locally from persecution and habitat destruction through wetland drainage for agriculture, residential and commercial development.
According to IUCN, the Water moccasin is locally common and widespread throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.
Water moccasins are important for the environment as they control the populations of their main prey, including fish, frogs, turtles, snakes and other reptiles.