Copperheads are not water snakes, though they are often mistakenly identified as such. This confusion stems from two main factors: habitat overlap, where copperheads sometimes venture near water, and the presence of the true aquatic venomous snake, the cottonmouth (water moccasin). Copperheads are primarily terrestrial, but their close relation to the cottonmouth often causes people to conflate the two species.
The Copperhead’s True Identity
The copperhead (Agkistrodon contortrix) is a venomous pit viper found across eastern North America. Although classified as a habitat generalist, it primarily prefers terrestrial environments such as deciduous forests, mixed woodlands, and rocky hillsides. They are frequently found in transition zones like forest edges and near suburban woodpiles.
While not truly aquatic, copperheads are sometimes found near low-lying, swampy regions or crossing shallow water. They are known for their distinctive coloration: a light reddish-brown or gray background overlaid with dark, hourglass-shaped crossbands. This pattern, combined with an unmarked, coppery-colored head, makes them highly camouflaged among leaf litter. Copperheads are ambush predators that often freeze when approached rather than fleeing, which contributes to the frequency of human bites.
Defining the Non-Venomous Water Snake
The snakes correctly referred to as “water snakes” belong to the genus Nerodia, including species like the common or northern water snake (Nerodia sipedon). These are non-venomous colubrid snakes that are highly semi-aquatic. They spend the vast majority of their time in or very near permanent water sources, thriving in diverse freshwater environments like lakes, rivers, ponds, and marshes.
Nerodia species are robust, heavy-bodied snakes with keeled scales and round pupils, distinctly different from pit vipers. When threatened, they exhibit defensive behavior, flattening their bodies and striking repeatedly. They also release a foul-smelling musk to deter predators. Their diet consists mainly of fish and amphibians, which they capture in their aquatic habitat.
The Source of the Confusion: The Cottonmouth Factor
The primary reason copperheads are mistakenly called water snakes is the existence of the cottonmouth (Agkistrodon piscivorus), a true aquatic venomous snake. Both the copperhead and the cottonmouth belong to the same genus, Agkistrodon. As close relatives, they share physical traits common to pit vipers, such as heat-sensing pits and a heavy body, which leads to frequent misidentification.
The cottonmouth is highly aquatic, found in swamps, marshes, and bodies of water throughout the southeastern United States. When a non-venomous water snake (Nerodia) is seen, it is often misidentified as a cottonmouth. This confusion is compounded because juvenile cottonmouths have a distinct, coppery-colored body and pattern often confused with the copperhead, reinforcing the myth that the copperhead is a water snake.
Key Distinctions for Identification
Distinguishing the terrestrial copperhead, the aquatic cottonmouth, and the non-venomous water snake involves observing specific physical and behavioral features. Pit vipers (copperheads and cottonmouths) have vertical, elliptical pupils, resembling a cat’s eye, while non-venomous water snakes have round pupils. Pit vipers also possess a distinct, triangular head shape due to their venom glands, and a visible heat-sensing pit located between the eye and the nostril, features absent in Nerodia species.
Regarding pattern, the copperhead has clean, dark brown, hourglass-shaped crossbands that are narrow across the top of the back. The cottonmouth often has a darker, less defined pattern that frequently becomes solid black or dark brown as the snake ages. Non-venomous water snakes, such as the Northern water snake, typically have dark bands or blotches that are widest across the top of the back, creating a pattern inverse to the copperhead’s hourglass shape.
Behavioral clues also aid identification, particularly how the snake rests in the water. The cottonmouth often swims with its body floating on the surface, while non-venomous water snakes typically swim with only their head visible above the water line. Furthermore, the cottonmouth is known for its unique defensive display: it opens its mouth wide to reveal the striking white interior, a behavior not exhibited by the copperhead.