Crotalus atrox is a venomous pit viper species found in the United States and Mexico. It is likely responsible for the majority of snakebite fatalities in northern Mexico and the second greatest number in the USA after C. adamanteus. No subspecies are currently recognized.

Common names

Western diamondback rattlesnake, western diamond-backed rattlesnake, Adobe snake, Arizona diamond rattlesnake, coon tail, desert diamond-back, desert diamond rattlesnake, fierce rattlesnake, spitting rattlesnake, Texan rattlesnake, Texas diamond-back (rattlesnake).

Description

Adults commonly grow to 120 cm in length. Specimens over 150 cm are infrequently encountered, while those over 180 cm are very rare. The maximum reported length considered to be reliable is 213 cm (Klauber, 1972). Males become much larger than females, although this difference in size does not occur until after they have reached sexual maturity.[4]

The color pattern generally consists of a dusty looking gray-brown ground color, but it may also be pinkish brown, brick red, yellowish, pinkish or chalky white. This ground color is overlaid dorsally with a series of 24-25 dorsal body blotches that are dark gray-brown to brown in color. The first of these may be be a pair of short stripes that extend backwards to eventually merge. Some of the first few blotches may be somewhat rectangular, but then become more hexagonal and eventually take on a distinctive diamond shape. The tail has 2-8 (usually 4-6) black bands separated by interspaces that are ash white or pale gray. There is a postocular stripe that is smoky gray or dark gray-brown and extends diagonally from the lower edge of the eye across the side of the head. This stripe is usually bordered below by a white stripe running from the upper preocular down to the supralabials just below and behind the eye.[4]

Though large and bulky in appearance, C. atrox can strike up to two-thirds of its body length. That’s about a three to four foot striking range for larger specimens. It strikes with two large, hollow fangs which inject venom into its prey eventually killing it (venom is lethal to small animals within minutes). The fangs are retractable and replaceable as venomous snakes lose and replace fangs often. Movement is in a rectilinear fashion (unlike sidewinders).

Diet

The diamondback eats small mammals and birds, and sometimes other reptiles, amphibians, fish, invertebrates, rabbits, mice, rats, gophers, sparrows, and ground squirrels. It eats every two to three weeks and swallows its food whole. The food is digested as it passes through the body. Its annual water consumption is about its body weight. In very dry areas it also absorbs water from its prey.

Behavior and reproduction

Western diamondbacks can live for more than twenty years, but life expectancy is typically shorter because of hunting and human expansion. Solitary outside of mating season, they are one of the more aggressive species found in North America because they rarely back away from confrontation. When threatened they usually coil and shake their rattle to warn an aggressor that it has stumbled upon something dangerous. There is suspicion that some rattlesnakes (and the diamondback in particular) which generally live around populated areas do not rattle as often because it leads to the snake’s discovery and consequent destruction. However, there is little available evidence of this hypothesis.

C. atrox, like other desert snakes, can go for up to two years without food in the wild. A 5½ month starvation study showed that the snakes reduced energy expenditures by an average of 80% over the length of the study. The snakes also feed from within on energy-rich lipid stores. The most interesting finding was that the snakes grew during the study, indicating that while the snake’s mass was shrinking, it was putting its resources into skeletal muscles and bone.[6]

In the winter the snakes will go into small caves to hibernate. This is about the only time that they do not want to bite each other. They can remember which cave they go to hibernate. The Western Diamondback also isn’t very aggressive when they are in the caves.

The snake is a poor climber and primarily hunts small mammals, but will also feed on birds, small reptiles and amphibians. They hunt (or ambush prey) at night or early morning using a type of infrared sense prominently found in pit vipers. Although adult specimens have no natural predators, hawks, eagles, and other snakes can prey on young or adolescent individuals.

Rattlesnakes, including C. atrox, are viviparous. Gestation period lasts six or seven months and broods average about a dozen young. However, the young only stay with the mother for a few hours before they set off on their own to hunt and find recluse, thus the mortality rate is very high.The Western Diamondback Rattlesnake is the most commonly encountered rattlesnake in Texas. The Western Diamondback is the longest rattlesnake in the state, and one of the two heaviest (the other is the Timber Rattlesnake). The record length is over 213 cm (84 in); adults found in the wild typically measure between 0.91-1.21 m (3-4 ft). Its common name does not come unearned; a series of diamond-shaped blotches runs down the length of its back, and each blotch is surrounded by a light border. A background coloration of tan or brown surrounds the blotches, and the dorsal coloration varies tremendously over its distributional range. This rattlesnake can easily be distinguished by its black and white tail, which also earns the western diamondback the name “coontail” (also, see below). Its off-white belly is usually unmarked, its anal scale is undivided, and its dorsal scales are extremely keeled, often in rows of 25 to 27 near midbody.