Description: A small species, adult specimens measure between 17 and 30 inches in length. Most adults are 19.5–31.5 inches in length. The females are larger than the males, which is unusual for this group of snakes. Usually, 21 rows of keeled dorsal scales occur midbody. Males have 141 or fewer ventral scales; females have 144 or fewer. It is sometimes referred to as the horned rattlesnake because of the raised supraocular scales above its eyes. This adaptation may help shade the eyes or prevent sand drifting over them as the snake lies almost buried in it.

The color pattern consists of a ground color that may be cream, buff, yellowish-brown, pink, or ash gray, overlaid with 28–47 dorsal blotches subrhombic or subelliptical in shape. In the nominate subspecies, the belly is white and the proximal lobe of the rattle is brown in adults. It has been described for the species to have the ability to display different coloration depending on the temperature—a process known as metachrosis.

Habitat: This snake generally inhabits open desert terrain with fine windblown sand, desert flats with sandy washes, or sand dunes sparsely vegetated with creosote bush or mesquite; sometimes it occurs in rocky or gravelly sites. In the Mojave Desert, snakes concentrated near washes and areas of relatively dense vegetation where mammal burrows were common, though in other areas this snake has been found to be more common where vegetation is sparse. During the daytime inactive period, individuals retreat into underground burrows or under bushes, or, at the end of activity at night, snuggle into sand with a minimum of the body exposed, remaining partially buried through daylight until conditions become too hot (then seeking shade). Hibernation sites are in in burrows of rodents or tortoises. In the eastern Mojave Desert, sidewinders hibernated in rodent burrows at the sand-alluvium interface. This terrestrial snake rarely climbs into vegetation.

Range: In the Southwestern United States, this species is found in the desert region of southeastern California, southern Nevada, southwestern Utah, and western Arizona. In northwestern Mexico, it is found in western Sonora and eastern Baja California.

Found in these States: AZ | CA | NV | UT

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: The Sidewinder preys mainly on lizards, pocket mice, kangaroo rats, and other small mammals. In many areas, lizards make up the bulk of their diet. Occasionally, a Sidewinder may take small birds and other 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 7–10 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 2–3 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 6-8 inches long. The birth takes only 2–3 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.

Subspecies: Three, all found in our region:
   Mojave Desert Sidewinder - (Crotalus cerastes cerastes)
   Sonoran Desert Sidewinder - (Crotalus cerastes cercobombus)
   Colorado Desert Sidewinder - (Crotalus cerastes laterorepens)

Taxonomy: