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Northern Cottonmouth

Agkistrodon piscivorus

iNaturalist Wikipedia

The Northern Cottonmouth is North America's only semiaquatic viper, a heavy-bodied master of the southern swamps. Famous for its white-mouthed threat display and its role as a top wetland predator, this snake is a fascinating subject for any backyard naturalist.

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Quick Identification

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Size

76–122 cm (30–48 inches) in length; heavy-bodied, weighing between 1.5–4.5 kg (3.3–10 lbs)

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Colors

Dark olive, brown, or black with dark crossbands; belly is pale with dark blotches; juveniles have bright patterns and yellow tail tips

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Key Features

Wedge-shaped head with heat-sensing pits
Dark 'mask' stripe running through the eye
Thick, heavy-set body with keeled scales
White, cotton-like interior of the mouth displayed when threatened

When You’ll See Them

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Activity pattern Active day and night

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Peak hours Dusk and night during summer; midday basking in spring and fall

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Season March-October

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Diet A generalist carnivore that eats fish, frogs, turtles, small alligators, birds, rodents, and even other snakes

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Habitat Wetlands, cypress swamps, marshes, slow-moving streams, and the edges of lakes or ponds

public Geographic range

Where Does the Northern Cottonmouth Live?

The Northern Cottonmouth is a quintessential resident of the North American Southeast. Its native range stretches from the Coastal Plain of southeastern Virginia, spanning down through the entirety of Florida and extending west across the Gulf States into eastern Texas and Oklahoma. In the Mississippi Valley, its presence can be traced as far north as southern Illinois and Missouri, where it thrives in humid, low-elevation environments near permanent water sources.

Basemap © OpenStreetMap contributors

1 Countries

1.2M km² Range

Least Concern Conservation

US United States

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iNaturalist / Verified observation data

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Behavior

The Northern Cottonmouth is a misunderstood and often maligned semiaquatic pit viper. While they have a reputation for being aggressive, they are actually quite reclusive and typically prefer to stand their ground or flee rather than strike. Their famous 'gaping' behavior—where they coil up and open their mouths wide to reveal the white lining—is a final warning to predators or humans to keep their distance. If left undisturbed, they are fascinating to watch as they navigate their watery domains with a buoyant, head-high swimming style.

These snakes are solitary hunters and highly efficient predators. They are one of the few vipers that are semi-aquatic, spending equal time basking on logs or low-hanging branches and hunting in shallow water. During the heat of the summer, they shift from being active during the day to being primarily nocturnal, utilizing their heat-sensing pits to locate warm-blooded prey in total darkness. While they are venomous and capable of a dangerous bite, they generally only interact with humans when stepped on or intentionally provoked.

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Camera Tips

To capture the Northern Cottonmouth on camera, focus your efforts on the 'transition zones' where water meets land. Look for fallen logs that receive direct sunlight for several hours a day; these are prime basking spots. Position your camera at a low angle, about 6 to 12 inches off the ground, to capture the snake's profile and its distinctive head shape. Because these snakes move slowly when basking but can strike quickly, a high-speed trigger and a fast shutter speed are essential for clear images.

Since Cottonmouths are frequently active at night during the summer, ensure your camera has a high-quality infrared flash that won't overexpose subjects at close range. Placing a camera near a known frog-breeding pool or a shallow stream crossing can yield excellent results, as these are high-traffic hunting grounds. Avoid using 'lures' or bait, as these snakes are wary and bait may attract larger predators that could damage your equipment or move the snake along too quickly.

Check your camera settings for a 'burst mode.' When a Cottonmouth gapes or moves into the water, you'll want multiple frames to catch the action. During the cooler months of spring and autumn, time your checks for mid-afternoon when the temperature is highest. Safety is paramount: always use a long mounting stick or reach-tool when adjusting cameras in swampy areas, and never place your hands into crevices or under logs where a snake might be resting.

Frequently Asked Questions

Their activity depends on the temperature. In the spring and fall, they are primarily diurnal, basking in the sun during the day. During the hot summer months, they become nocturnal, hunting at night when it is cooler.

It is generally not recommended to intentionally attract venomous snakes to a residential backyard. However, they are naturally drawn to properties with permanent water sources like ponds, thick vegetation for cover, and a healthy population of frogs or rodents.

They are opportunistic feeders with a very broad diet. They commonly eat fish, amphibians (frogs and salamanders), small mammals, birds, and other reptiles, including smaller snakes and baby turtles.

Yes, they can be common in suburbs that border wetlands, marshes, or retention ponds. They often navigate through drainage ditches and can occasionally be found in swimming pools or under damp porches.

Cottonmouths swim with their entire bodies buoyant on the surface, whereas non-venomous water snakes typically swim with only their heads above water. Cottonmouths also have a thicker body, a distinct dark 'mask' through the eye, and vertical pupils.

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