Crotalus atrox
western diamondback rattlesnake

The Western Diamondback Rattlesnake ranges from central and western Texas, through southern New Mexico and Arizona, and into southern California. It also extends well into central Mexico.

Western Diamondback Rattlesnakes inhabit dry, rocky, shrub-covered terrain where they can conceal themselves inside crevices in the rocks or in mouse holes.

Body length: ~1.5 meters Body weight: up to 6.7 kg. Crotalus atrox has a plump body, short tail, and a broad triangular head. Like all Pit Vipers, it has a pit organ, which is situated in an indentation of the upper jaw, between the nostril and eye. The pit is about 5 mm deep, with an outer and inner chamber separated by a thin membrane. The membrane senses very slight temperature differences between the snake's inner and ambient temperatures. The Western Diamond Rattlesnake also has the self-named rattle on the end of the tail. Each link of the rattle is the remnant of a molted skin; as the snake molts, the last scale loosens but does not fall off. As the snake ages, new rattles are formed with each molt, while old rattles simultaneously fall off. This species has long, tubular fangs, which are characteristic of venomous snakes.

Crotalus atrox can be a yellowish gray, pale blue, or pinkish ground color. The diamond shapes down its length are dark with pale white borders. The tail is white with jet-black rings. The head markings include a pale oblique band from nostril to upper labials, and a similar but narrower band behind the eye.

Western Diamondback Rattlesnakes are aggressive and easily excitable. This species causes more fatalities than any other snake in the United States. They are not necessarily apt to attack offensively, but are rather highly defensive. Their rattles are used as a warning sign. Although the rattles were once thought to be used for intraspecific communication, this belief has been discredited because Rattlesnakes are actually deaf. Their rattles can activate at 40 to 60 cycles a second. The Western Diamondback assumes the threat posture by slightly flattening the body, rolling it together into a spiral, lifting the forebody from the ground into an S-shape, and keeping the tail raised and the rattle rattling.

Ritualized fighting has been observed in C.atrox males. Fighters lift their forebodies up 80 cm. in the air, wrap them around each other, orienting head to head. They keep moving in a surging movement back and forth until one of the males backs off. Common predators of C.atrox include hawks, bald eagles, roadrunners, and wild turkeys.

In the fall, Western Diamondback Rattlesnakes begin migrating to winter hibernacula. In warmer habitats, these hibernacula are fairly makeshift, being found in rock crevices or convenient holes. In colder habitats, such as prairie grasslands, populations are forced to use the holes and tunnels of burrowing mammals, especially the prairie dog. Although prairie dogs may block off the Rattlesnake with an earthen plug, these animals tend to abandon burrows that have been taken over by snakes. During hibernation, populations concentrate as several individuals den together. In warmer habitats, where the hibernation season is shorter and hibernacula more makeshift, fewer individuals congregate. Rattlesnakes are known to be nocturnal hunters, and are less active diurnally

Crotalus atrox preys on small mammals and birds, and sometimes other reptiles and amphibians, and even fish and invertebrates. In a matter of seconds, individuals of this species can leave a fatal bite by injecting venom into its prey. The teeth often remain inside the prey, but are replaced 2 to 4 times annually by reserve teeth. Muscles surrounding the venom glands control the amount of venom released, as well as the flow of venom to the fangs. Rattlesnakes swallow their prey whole, then digest as the food passes though the body. Rattlesnakes in the wild eat every 2 to 3 weeks on average. Annual water intake in rattlesnakes roughly equals body weight. In drier climates, where water availability is lower, moisture is assimilated from prey. More water is absorbed during shedding due to desiccation and evaporation.

Reproduction

Behavior

Habitat

Biomes: desert, scrubland

The Western Diamondback Rattlesnake is notorious for its fatal bite, and has instilled a certain fear and paranoia in humans.

Crotalus atrox is good at controlling rodent problems. It also keeps well in captivity; this makes it a good educational resource in zoos and snake shows. Rattlesnakes are key in Native American culture, in which their flesh, oil, and venom have been used as a food source and as a basis for medicinal preparations for a long time. Rattlesnake skins are regularly used for skin products such as shoes and belts. Rattlesnakes are also prominent on the live-snake market, where they sell for $2 to $3 per foot (Klauber 158).

Largely due to the risk and danger of snake bites, rattlesnakes have come to instill paranoia and fear in humans. As a result, there are numerous forms of rattler control, such as bounties, poisons, traps, and the destruction of food supplies and refuges. However, Crotalus atrox is a highly successful and fertile species, and therefore are not currently threatened by any forms of mass destruction or species control.