Arizona is home to more types of rattlesnakes than any other state in the United States, showcasing an impressive biological diversity within its arid and mountainous landscapes. The state’s unique geography, which ranges from scorching low deserts to high-elevation sky islands, provides habitat for approximately 13 different species of these fascinating reptiles. Rattlesnakes belong to the subfamily Crotalinae, making them a type of pit viper, all of which share certain specialized anatomical features.
The Most Widespread and Largest Species
The Western Diamondback Rattlesnake (Crotalus atrox) is the most recognizable and widespread species encountered across Arizona. It often grows to lengths between four and six feet, though some specimens can reach up to seven feet, making it one of the largest rattlesnakes in North America. Its body is typically pale gray, tan, or reddish, patterned with dark, pale-bordered diamond shapes running down its back. A distinctive feature is the tail, which is banded with stark, alternating black and white rings just before the rattle, often called a “raccoon tail.” The Western Diamondback is a generalist, occupying diverse habitats from desert flats and rocky foothills to grasslands and mountainous terrain up to 6,500 feet.
The Mohave Rattlesnake (Crotalus scutulatus) is a prominent species common throughout the state’s lower elevations, particularly in open desert flats and semi-desert grasslands. Its coloration is often a pale olive, tan, or greenish-gray, which sometimes leads to the nickname “Mohave Green.” This snake is notable for its highly toxic venom, which often contains a potent neurotoxin that affects the nervous system. Distinguishing the Mohave from the Western Diamondback can be subtle, but the Mohave typically has white tail bands that are noticeably wider than its black bands, a reverse pattern of the diamondback. It is primarily nocturnal during the hottest months, hunting small mammals and lizards.
Rattlesnakes Adapted to Specific Arizona Regions
Sidewinder
The Sidewinder (Crotalus cerastes) is adapted to the state’s low, sandy deserts and dune fields, particularly in the western and southwestern regions. Its defining characteristic is “sidewinding” locomotion, a movement that involves throwing its body in S-shaped curves to move sideways across loose sand. This unique gait minimizes the amount of the snake’s body touching the hot surface, preventing overheating. The Sidewinder is also identified by a horn-like scale projecting above each eye, which helps shade its eyes and prevents sand from accumulating when the snake is buried. This is a relatively small species, typically measuring less than two feet long.
Tiger Rattlesnake
The Tiger Rattlesnake (Crotalus tigris) is a geographically restricted species, found predominantly in the Sonoran Desert’s rocky canyons, foothills, and arid mountains. This snake has a comparatively small head and a large rattle, a proportion that is unusual among rattlesnakes. Its pattern consists of numerous dark crossbands that often appear faded or indistinct, resembling a tiger’s stripes. Its preference for rocky slopes and crevices is reflected in its diet of small mammals and lizards. Its venom is recognized as one of the most toxic of any rattlesnake, although the snake typically yields a low volume when striking.
Black-Tailed Rattlesnake
The Black-Tailed Rattlesnake (Crotalus molossus) primarily inhabits rocky, mountainous areas and sky islands across southern Arizona. As its name suggests, this species has a uniformly black tail that contrasts sharply with the rest of its body, which can be yellow, olive, or greenish-gray. These snakes are often found in canyon walls and high-altitude woodlands, sometimes even climbing into low trees or shrubs to bask or ambush prey. The Black-Tailed Rattlesnake is known for its relatively calm disposition but uses its distinctively colored tail to warn off perceived threats.
Identifying Features Common to All Arizona Rattlesnakes
Rattlesnakes share several biological traits that classify them as pit vipers. The head shape is distinctly triangular and broad due to the large venom glands located toward the rear of the jaw. A defining feature is the presence of a pair of loreal pits, small, deep depressions situated between the eye and the nostril on each side of the face. These organs are highly sensitive to infrared radiation, allowing the snake to detect the heat signature of warm-blooded prey, even in complete darkness.
The eyes of rattlesnakes have vertically elliptical pupils, a common characteristic of nocturnal or crepuscular hunters. The most obvious shared feature is the rattle itself, a series of interlocking segments made of keratin, the same material found in human fingernails. A new segment is added each time the snake sheds its skin, and the vibration of these segments against one another creates the characteristic buzzing warning sound. The body scales are typically keeled, meaning they have a ridge down the center, giving the snake a rough texture that aids in camouflage and movement.