Missouri is home to several venomous snake species. Understanding their characteristics and behaviors is important for safety and coexisting with these reptiles.
Venomous Snake Species in Missouri
Missouri hosts five species of venomous snakes, all of which are pit vipers: the Eastern Copperhead, Western Cottonmouth, Timber Rattlesnake, Western Pygmy Rattlesnake, and Eastern Massasauga Rattlesnake. The most commonly encountered venomous snake across the state is the Eastern Copperhead. This species typically measures 24 to 36 inches long and exhibits a gray, copper, tan, or pinkish-tan body with distinctive dark brown hourglass-shaped bands. Copperheads inhabit diverse environments, including rocky, wooded hillsides, brushy areas near creeks, and swamps, often relying on their camouflage among dead leaves.
The Western Cottonmouth, also known as the water moccasin, is a heavy-bodied snake found primarily in southeastern Missouri’s swamps, sloughs, and oxbow lakes, as well as in scattered populations in Ozark streams. Adults usually range from 30 to 42 inches in length and are dark olive-brown to nearly black, often with indistinct dark crossbands. Young cottonmouths are lighter with distinct bands and a greenish-yellow tail tip.
Timber Rattlesnakes are Missouri’s largest venomous snakes, growing 3 to 5 feet. Their bodies are typically yellow, tan, brown, or gray, marked with dark brown V-shaped or banded patterns, and they possess a prominent rattle at the tail’s end. These rattlesnakes prefer mature forests, heavily wooded hillsides, and rocky bluffs, congregating in dens during colder months.
The Western Pygmy Rattlesnake is a smaller species, usually 15 to 20 inches long, reaching up to 33 inches. They have a brownish-gray body with small dark brown or black blotches and a narrow orange-brown dorsal stripe. These snakes are found in glades, second-growth forests near rock ledges, and along forest edges, particularly on south-facing, rocky, and partially wooded hillsides in the Ozarks.
The Eastern Massasauga Rattlesnake, a state-endangered species, is typically light to dark gray or gray-brown with dark brown or black blotches. These medium-sized rattlesnakes range from 18 to 30 inches and are found in marshes and moist prairie habitats, especially in north-central and northwestern Missouri.
Key Features for Identification
Venomous snakes in Missouri share common characteristics that distinguish them from non-venomous species. A primary indicator is the presence of a heat-sensing pit, a small, deep indentation located between the eye and nostril on each side of the head.
Another distinguishing feature is the shape of their pupils, which are elliptical or cat-like, appearing as vertical slits in bright light. In contrast, most non-venomous snakes in Missouri have round pupils.
While venomous snakes often possess a triangular or spade-shaped head that is distinct from their neck, several non-venomous species, such as water snakes and hog-nosed snakes, can flatten their heads when threatened, mimicking this appearance.
The scales on the underside of a venomous snake’s tail typically appear in a single row from the anal plate to the tail tip. Non-venomous snakes, conversely, usually have a double row of scales along the underside of their tails. Rattlesnakes, specifically, have a segmented rattle at the end of their tail, though many non-venomous snakes can vibrate their tails to mimic a rattling sound when agitated.
Staying Safe and Responding to Bites
Preventing snake encounters requires being mindful of your surroundings. Wear appropriate footwear, such as boots, when walking in wooded or brushy areas, and watch where you step. Avoid placing hands into unseen areas like rock crevices, logs, or dense brush piles where snakes might be resting. Snakes generally are not aggressive and will usually try to escape if given the opportunity; most bites occur when individuals attempt to handle, capture, or kill a snake. If you encounter a snake, maintain a safe distance and do not approach or provoke it, slowly backing away to allow it to move off on its own.
Should a snake bite occur, it is important to remain calm and seek immediate medical attention, even if you are unsure if the snake was venomous. Call 911 right away. While waiting for medical help, move to a safe area, keep the bitten limb still, and position it slightly below the level of the heart to help slow venom spread. Remove any jewelry or tight clothing from the affected area in case swelling occurs. Do not attempt to cut the wound, suck out the venom, apply ice, or use a tourniquet, as these actions can worsen the outcome.