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Types of Pit Viper Snakes in the American Southwest

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A hissing rattlesnake is one of the most iconic images of the Southwest. Striking fear into the heart of early settlers and modern-day residents alike, these snakes serve important functions in local ecosystems and thrive in the hot, arid lands of Texas, New Mexico, Arizona and California.

Pit Viper Biology

Pit vipers (Crotalidae) are a family of snakes found in the Americas and Asia; they are absent from Europe and Africa where the “true” vipers (Viperidae) exist. All pit vipers possess a small indentation on each side of the face, between the eye and the nostril. Inside these indentations, sensitive nerve endings collect thermal data about the snake’s environment. With these thermoreceptive pits, the snakes can see predators and prey in the dark as well as find warm basking locations. All pit vipers have large, folding fangs that deliver potent venom used to incapacitate prey and deter predators. All pit viper species found in America are born live, already possessing venom and fangs. Most pit vipers are ambush hunters that prefer rodents, lizards and frogs as prey.


Though found over much of the United States and as far south as Argentina, rattlesnakes are most prevalent in the American Southwest. Due in part to the varied ecology of the state, Arizona holds the distinction of having the most native species, according to the American International Rattlesnake Museum. The Arizona Game and Fish Department recognizes 36 species of rattlesnake, of which 13 are native to the state. Commonly seen species in the region include western diamondback rattlesnakes (Crotalus atrox), Mojave rattlesnakes (Crotalus scutulatus),sidewinders (Crotalus cerastes) and black-tailed rattlesnakes (Crotalus molossus). If you're brave enough to venture into the sparsely populated hills and mountains, you may be treated to the sight of a banded rock rattlesnake (Crotalus klauberi) or the very rare ridge-nosed rattlesnake (Crotalus willardi), which is protected by law. Rattlesnakes use their namesake rattle to deter predators when their camouflage fails them. The rattle forms from scales retained during the shedding process.


Besides rattlesnakes, the only other pit viper that lives in the American Southwest is the broad-banded copperhead (Agkistrodon contortrix laticinctus), which is only found as far west as central Texas. Broad-banded copperheads are small snakes, rarely exceeding 30 inches in length. Though the copperhead possesses fangs and venom glands, its venom yield is low and not as toxic as that of most rattlesnake species. These snakes blend in well with their upland habitats and ambush their rodent, lizard and frog prey as it walks by. Like rattlesnakes, copperheads will rattle their tails when alarmed, though they lack the loud rattle of their cousins.

Pit Viper Encounters

Pit vipers -- particularly small individuals -- have a variety of predators to avoid. To a rattlesnake or copperhead, virtually any large animal is a potential predator; accordingly, pit vipers avoid humans when at all possible. Most pit viper bites occur when a human unknowingly steps on one of the venomous snakes -- when the snake feels threatened it bites to defend itself. By simply watching where you put your hands and feet, you can avoid these negative encounters. It's important to protect pit vipers, as they keep the rodent population in balance with the ecosystem. If a pit viper bites you, do not touch the wound and proceed directly and calmly to the hospital. With prompt medical attention, bites are rarely fatal; Arizona Poison Centers report that only 1 percent of rattlesnake bites are fatal for adults.