Crotalus atrox - Western Diamond-backed Rattlesnake

Venomous

The venom of this snake is potentially dangerous to humans.

Size

Adults grow to 30-90 inches (76-229 cm). Most snakes encountered are from 1 to 4 feet in length.

Appearance

The largest rattlesnake in California, and in the West. Heavy-bodied, dangerously venomous, with a thin neck and a large triangular head. Pupils are elliptical. Scales are keeled. Sometimes 3, but usually 4 or more small scales occur on top of the head between the supraocular scales. (The Northern Mojave Rattlesnake has 2 large scales between the supraocular scales.)

The ground color and the intensity of the pattern are variable, often matching the habitat; grey, brown, olive, tan, or yellowish. Diamond-shaped blotches on the back are brown or black, with light edges. Broad black and white rings, fairly equal in width, circle a thick tail with a rattle, consisting of loose interlocking segments, at the end. A new rattle segment is added each time the skin is shed. Newborn snakes do not have a rattle - just a single button which does not make a sound. A light stripe extends from behind the eye diagonally to the upper lip in front of the corner of the mouth crossing over the lip. (The posterior light stripe of the Northern Mohave Rattlesnake extends back beyond the corner of the mouth and does not cross the lip.)

Similar to and easily confused with the Northern Mohave Rattlesnake, though there is little range overlap in California. Also similar to and easily confused with the Red Diamond Rattlesnake, but in California the ranges of these two snakes barely meet, and the Red Diamond Rattlesnake is typically light reddish brown or red in color.

A pit viper with pits on the sides of the head which sense heat. These heat sensors help the snake to locate prey by their warmth. Long, hollow, movable fangs connected to venom glands inject a very toxic venom which quickly immobilize the prey. The snake can control the amount of venom injected and the fangs are replaced if broken. Bites on humans are potentially deadly without immediate medical treatment. Even a dead snake can bite and inject venom if the jaws reflexively open when they are touched.

Behavior

Primarily nocturnal during periods of excessive daytime heat, but also active during daylight when the temperature is more moderate. Not active during cooler periods in Winter.

An ambush hunter, it typically sits near the trail of a mammal, waiting for it to pass by, then strikes at and releases the prey. The snake then follows the trail of the envenomated animal and swallows it whole.

When alarmed, a rattlesnake shakes its tail back and forth. The movement rubs the rattle segments together producing a buzzing sound which serves as a warning. When disturbed, in self-defense Western Diamond-backs will often aggressively hold their ground, raising the head high in a striking coil with the tail elevated and rattling, and hissing loudly. Juveniles are born with only a silent button at the end of the tail.

Diet

Eats small mammals, birds, lizards. Juveniles sometimes eat large insects and frogs.

Reproduction

Live-bearing. Males engage in ritual combat mostly during the breeding season to defend territory. Necks and forebodies are intertwined, with the stronger snake slamming the smaller one to the ground until the weaker snake leaves the area.

Range

Found in southeast California in Imperial, Riverside, and San Bernardino Counties. Ranges east to Arkansas and East Texas, and south through Arizona, New Mexico and Oklahoma into Mexico.

Habitat

Inhabits arid and semiarid areas including mountains, deserts, canyons and rocky vegetated foothills, generally less than 1000 ft. elevation (300 m).