The Copperhead and the Cottonmouth are often mistaken for each other across the United States, but they are distinct species. Both are venomous snakes with unique characteristics and behaviors. Correctly identifying the differences between them is important for safely navigating the environments they inhabit.
Classification: Addressing the Shared Family Tree
The Copperhead and the Cottonmouth are close biological relatives that share a common lineage. Both snakes belong to the family Viperidae, which groups them with all vipers and pit vipers. This classification means they share hinged fangs and specialized venom glands.
Both species belong to the same genus, Agkistrodon, commonly known as American moccasins. The Copperhead is Agkistrodon contortrix, and the Cottonmouth is Agkistrodon piscivorus. This shared genus explains their similar features, such as the triangular head shape and the heat-sensing loreal pits. These pits allow them to detect warm-blooded prey.
Distinct Physical Features for Identification
The most obvious way to tell the two species apart is by observing their coloration and body structure. The Copperhead is named for its pale to reddish-brown coloration, often with a distinct coppery sheen on its head. Its body pattern consists of dark brown, hourglass-shaped crossbands that are narrow along the spine and wide on the sides. Copperheads are generally smaller and more slender, typically reaching lengths of 2 to 3 feet as adults.
The Cottonmouth, also known as the Water Moccasin, is noticeably more robust and thick-bodied, usually growing to an average length of 3 to 4 feet. Adult Cottonmouths tend to be much darker, ranging from olive to deep brown or almost uniformly black, which can obscure their crossband pattern. When threatened, the Cottonmouth coils and opens its mouth to display the bright white, cotton-like interior that gives the species its common name.
Geographic Range and Preferred Habitats
The environments these snakes prefer represent a significant difference between the two species. Cottonmouths are the only semi-aquatic venomous snake in North America, with a strong association with water. They are found almost exclusively in or immediately near swamps, marshes, drainage ditches, and the slow-moving edges of lakes and rivers. Their range is largely confined to the southeastern United States, extending from southeastern Virginia west into central Texas.
Copperheads, in contrast, are far more terrestrial, preferring dry, wooded hillsides, rocky outcrops, and forests. They are highly adaptable and often thrive in suburban and urban areas, hiding under wood piles, landscaping timbers, and debris. The Copperhead’s geographic range is much broader, spanning the Eastern and Midwestern United States.