Description: Adult size 25 inches. The Sonoran Desert Sidewinder looks as if it has horns over its eyes and is sometimes called the horned rattlesnake. These horns are actually upturned scales, and are not truly horns. The body is typically a sandy tan, gray, or cream color and is patterned with dark blotches of brown or grey on the back and sides. There is a dark cheek-stripe on both sides of the head that starts at the eye and runs diagonally down and backwards above the mouthline. The tail often has a few to several rings. The end of the tail has a rattle on it. This form has the following distinguishing characteristics: the proximal rattle-matrix lobe is black in adult specimens, the ventral scales number 132 to 144/138 to 148 in males/females, the subcaudals number 18 to 24/14 to 19 in males/females, and there are usually less than 21 rows of midbody dorsal scales. It can be distinguished from the other two subspecies of C. cerastes by range, as well as having a black proximal rattle segment ("button" connecting the rattle to the tail).

Habitat: Typical habitat includes arid sand flats, sand dunes, and open creosote scrublands.

Range: Found in the United States from Yuma, Maricopa, Pima and Pinal counties in Arizona, southward into Sonora, Mexico. The type locality given is "near Gila Bend, Maricopa County, Arizona".

Found in these States: AZ

Venom: These snakes are venomous, but possess a weaker venom than many other rattlesnakes. This, together with the smaller size of their venom glands, makes them less dangerous than their larger relatives. Regardless, any rattlesnake bite can be fatal and should be taken seriously and medical attention sought immediately.

Envenomation can cause pain, swelling, hemorrhagic bleb formation, and ecchymosis (i.e., bruising). Swelling, while not particularly severe, occasionally may involve entire limbs and the trunk. Envenomation's systemic symptoms include nausea, dizziness, chills, coagulopathy (blood disorders), and shock. There is an account of a man who had been bitten on the first joint of the index finger of the right hand, with only a single fang penetrating. Although the bite was described as no more painful than a pin prick, a doctor was seen within about 25 minutes, and 10 cm3 of antivenin were administered. Within 2.5 hours, his entire arm was swollen and the pain was severe, "as if the arm were soaked in a bucket of boiling oil."

Ovine-derived antivenom, CroFab, for North American pit viper envenomation, has been widely available since 2001. Consultation with a local expert or regional poison control center should be obtained before administering antivenom. The previous antivenin (ACP) is no longer manufactured.

Diet: It is active at night, laying in ambush partially covered in sand. Prey includes lizards, rodents and even small snakes.

Reproduction: Females produce up to 18 young, with an average of about 10 per litter. Like most other viperids, the young are born enveloped in thin embryonic membranes, from which they emerge shortly after being expelled from the mother. The young stay with their mother in a burrow for 7 to 10 days, shed for the first time, then leave their natal burrow. During this time, the mother is thought to guard and protect them from predators.

Sidewinders mature at 2 to 3 years of age, are capable of reproducing annually, and give birth to live young. Some females skip reproductive opportunities. Some might even skip two years if the food supply is scarce. Sidewinders mate in April through May and sometimes in fall. When the male and female mate, the male snake crawls along the female's back, rubbing her with his chin to stimulate or arouse her. The male then will wrap his tail around her tail, and then will try to bring their cloacae together. The cloaca is the posterior body opening through which snakes both excrete waste and reproduce. If the female wants to mate, she lifts her tail and allows him to mate with her. The snakes can mate for several hours, and if one of the snakes decides to move, the other is dragged along. Females might mate with several males in a season. Females give birth to five to 18 young in late summer to early fall. The young are born 6 to 8 inches long. The birth takes only 2 to 3 hours altogether. Within a few minutes of being born, the newborn sidewinder escapes from a thin, transparent membrane. The young stay at their natal burrow for 7–10 days until they shed, and then they disappear and have no future contact with their mother or their littermates. While the density of sidewinders can be up to one individual per hectare, they rarely encounter each other except during mating season.

Status: Listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.

Taxonomy: