The names “cottonmouth” and “water moccasin” often lead to confusion, causing many to wonder if they refer to the same snake.
The Truth About the Names
Cottonmouths and water moccasins refer to the same snake. “Water moccasin” is a common, informal name, while “cottonmouth” is the more widely accepted common name. The scientific name for this snake is Agkistrodon piscivorus, a Latin name that refers to its fish-eating habits. The name “cottonmouth” comes from the bright white interior of its mouth, displayed as a warning when threatened. Regional variations contribute to the confusion, with “water moccasin” prevalent in some areas, alongside other local names like “black moccasin” or “swamp moccasin.”
Identifying the Cottonmouth
Cottonmouths are stout-bodied pit vipers typically ranging from 30 to 48 inches long, though some individuals can grow larger. Their color varies from dark brown or black to olive, often with broad, dark crossbands that may become obscure in older individuals, making them appear uniformly dark. They have a triangular-shaped head, distinctly broader than their neck, and vertical, cat-like pupils. Like all pit vipers, they possess heat-sensing pits between their eyes and nostrils to detect prey.
Cottonmouths are semi-aquatic, preferring habitats near water such as swamps, marshes, and river edges. They are often seen basking on rocks, logs, or stumps. When swimming, most of their body, including their head, floats above the water’s surface. If threatened, they often coil and gape their mouth wide, revealing the pale, cottony-white interior as a warning.
Understanding Its Venom
The cottonmouth possesses a potent hemotoxic venom, which primarily affects blood cells and tissues. A bite can cause severe, immediate pain, rapid swelling, skin discoloration, and tissue damage around the bite area. The venom prevents blood from clotting, potentially leading to internal bleeding. While cottonmouth bites are serious and require immediate medical attention, human fatalities are rare, accounting for less than 1% of snakebite deaths in the U.S.
Bites typically occur when the snake feels provoked or cornered. Approaching these snakes with caution and respecting their space is important. Seeking prompt medical care for any suspected bite is crucial for proper treatment and recovery.
Distinguishing from Look-Alikes
Cottonmouths are often confused with non-venomous water snakes (Nerodia genus), which share similar aquatic habitats and can also be dark in coloration. A key difference is swimming posture: cottonmouths float with most of their body on the surface, while water snakes typically submerge more. Cottonmouths have a broad, triangular head, unlike the narrower heads of water snakes. However, some water snakes can flatten their heads when threatened, mimicking this shape.
Another distinguishing characteristic is pupil shape; cottonmouths have vertical, slit-like pupils, similar to a cat’s, while water snakes have round pupils. Defensive behaviors also differ; cottonmouths often stand their ground and display their white mouths, whereas water snakes are more likely to flee or may flatten their bodies and bite. Juvenile cottonmouths often have more distinct banding and a bright yellow or greenish tail tip, which fades with age and is used to lure prey.