Texas is a state known for its size and biological diversity. It includes a large number of native snake species, which occupy nearly every ecosystem from coastal marshes to arid deserts. While the public often uses the term “poisonous,” the accurate scientific term for an animal that injects its toxins through a bite is “venomous.” For clarity, this article will use the commonly recognized term. Understanding the species present is a proactive step toward safety and promotes respect for these reptiles, which control rodent populations.
The Specific Number of Poisonous Snakes in Texas
Texas is home to over 100 different species and subspecies of snakes, but only 15 are venomous. These 15 types fall into four major groupings: rattlesnakes, copperheads, cottonmouths, and coral snakes. Most venomous snakes belong to the Pit Viper family (Crotalinae). Pit Vipers are divided into three groups: rattlesnakes (genera Crotalus and Sistrurus), copperheads (Agkistrodon contortrix), and cottonmouths (Agkistrodon piscivorus). Rattlesnake species account for the largest portion of the total count, with multiple types found across various regions.
The fourth major group is the Texas Coral Snake (Micrurus tener), the state’s only representative from the Elapidae family. The count of 15 includes various species and subspecies, such as the Western Diamondback Rattlesnake, the Timber Rattlesnake, and the three subspecies of copperheads.
Distinct Features of Venomous Species
Venomous snakes in Texas are separated by two major families: Pit Vipers and Elapids. Pit Vipers share several distinct traits. The most noticeable feature is the triangular or spade-shaped head, which appears wider than the neck due to the venom glands. Pit Vipers are named for the deep sensory pit located between the eye and the nostril. This specialized organ is a heat-sensing mechanism that allows the snake to detect warm-blooded prey, even in darkness.
Their eyes feature vertically elliptical pupils, resembling a cat’s eye, unlike the round pupils found in most non-venomous snakes. Pit Vipers have a single row of scales underneath their tail, known as subcaudal scales, although this feature requires close inspection.
The Texas Coral Snake (Elapidae family) lacks the specialized pit organ. These snakes are recognized by their distinct pattern of bright red, yellow, and black bands that encircle the body. Distinguishing the Coral Snake from non-venomous mimics, such as the Milk Snake, relies on the order of the color bands. The venomous Coral Snake has red bands touching yellow bands—a sequence “Red next to yellow will kill a fellow”—while harmless mimics have red bands touching black bands.
Geographic Distribution Within Texas
The vast and varied geography of Texas means that the distribution of its venomous snakes is not uniform across the state. Rattlesnakes are the most widespread group, with different species occupying nearly all of Texas’ diverse ecosystems. The Western Diamondback Rattlesnake, for example, is the most common and can be found in all but the easternmost portion of the state, thriving in desert, prairie, and scrubland habitats. Other rattlesnake species, such as the Mottled Rock Rattlesnake, are restricted to the mountainous, rocky areas of the Trans-Pecos region in West Texas.
The Copperhead is also geographically dispersed, with its three subspecies found across the eastern third of the state and scattered populations extending into Central and West Texas. Copperheads are typically associated with forested areas, wooded bottomlands, and rocky outcrops.
Cottonmouths, also known as water moccasins, have a much more specialized habitat preference, limiting their distribution to the eastern half of the state. They are almost exclusively found in or near water, inhabiting swamps, marshes, sluggish waterways, and river floodplains. The Texas Coral Snake is largely confined to the southeastern portion of Texas, favoring wooded habitats with thick leaf litter or areas with loose soil where they can burrow.