The water moccasin, also known as the cottonmouth, is a heavy-bodied, venomous pit viper (Agkistrodon piscivorus). It is the world’s only semi-aquatic viper, thriving in the wetland ecosystems of the southeastern United States. Its preferred habitat includes slow-moving or stagnant water bodies, such as cypress swamps, marshes, streams, and the shores of lakes and ponds. The water moccasin is a formidable predator whose feeding habits reflect the diverse prey available in these aquatic and terrestrial settings.
The Core Diet: Aquatic and Terrestrial Prey
The adult water moccasin is an opportunistic carnivore, consuming a wide array of vertebrates and occasionally carrion. Fish and amphibians form the bulk of its diet. Specific aquatic prey includes various species of fish, such as bass and catfish, which are often targeted when they are slow-moving or trapped in shallow water.
Amphibians, including frogs and salamanders, are common food items, ranging from smaller southern leopard frogs to large bullfrogs. The diet extends beyond cold-blooded aquatic life to include reptiles, small mammals, and birds. Reptilian prey consists of young turtles, lizards, and other snakes, including non-venomous water snakes and smaller water moccasins (cannibalism).
Small mammals, such as shrews and rodents, are often consumed when they venture near the water’s edge. Birds that are downed or nesting close to the water are also taken opportunistically. This flexibility allows the snake to exploit available food sources across both its aquatic and terrestrial hunting grounds.
Specialized Foraging and Hunting Techniques
The water moccasin employs specialized behaviors to capture its diverse prey, using both active hunting and patient ambush techniques. When hunting in the water, the snake holds its body high on the surface, allowing it to corner fish in shallow areas or against the bank. While capable of active pursuit, they often rely on lying in wait near the water’s edge or semi-submerged.
A specialized technique observed in younger snakes is caudal luring, where the snake wiggles the bright, yellowish tail tip to mimic a worm or insect larva. This visual lure is an act of aggressive mimicry, drawing unsuspecting prey like frogs and lizards within striking range. The snake’s venom is administered through a bite, and its primary function is to immobilize or kill the prey.
The snake uses its heat-sensing facial pits, characteristic of all pit vipers, to locate and accurately strike warm-blooded prey, even in darkness. After delivering a venomous bite to a large animal like a rodent, the moccasin will often strike and release. It then tracks the debilitated animal using the chemical cues of the venom and its thermal signature. Conversely, smaller prey like fish and frogs are typically held firmly in the jaws immediately after the strike and then swallowed.
How Diet Changes with Age and Environment
The dietary composition of the water moccasin shifts as the snake matures, corresponding with changes in body size and hunting efficacy. Juvenile water moccasins prefer smaller, cold-blooded prey, frequently consuming insects, insect larvae, and small invertebrates. This early diet is often supplemented with small fish and amphibians, which are more readily caught by the smaller snakes.
The young snakes rely heavily on caudal luring to secure these small food items, a behavior that becomes less common in adulthood. Adult snakes transition to a diet dominated by larger vertebrates, including fish, mammals, and birds. The adult’s larger size allows it to overpower and subdue more substantial meals, providing greater caloric return.
Environmental conditions also dictate seasonal and regional variations in the diet due to the snake’s opportunistic nature. For instance, during drought, the concentration of stranded fish and tadpoles in drying water bodies provides an easy, temporary feast. Local prey availability can influence sex-specific diet differences, with some studies showing adult males consuming more fish while adult females target other snakes and squamates.