The sidewinder is a venomous snake found in the desert regions of North America. The color pattern of these snakes 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. Their belly is white and the proximal lobe of the rattle is brown in adults. The coloration of sidewinders can change depending on the temperature-a process known as metachrosis. Females in this species are larger than males, which is unusual for this group of snakes.
Sidewinders are found in the southwestern United States and northwestern Mexico. In the southwestern United States, these snakes are found in southeastern California, southern Nevada, southwestern Utah, and western Arizona. In northwestern Mexico, they are found in western Sonora and eastern Baja California. Sidewinders live in desert landscapes including sandy washes, sand dunes with thickly vegetated areas, and rocky areas.
Sidewinders are terrestrial snakes and rarely climb into vegetation. They are nocturnal during hot months and become diurnal during the cooler months, which is roughly from November to March. In order to stay cool, sidewinders spend most of their time in rodent burrows, the rest time is spend lying coiled up partially buried in the sand waiting on prey. These snakes take their common name from an unusual form of locomotion. As their body progresses over loose sand, they form a letter J-shaped impression, with the tip of the hook pointing in the direction of travel. Sidewinder rattlesnakes can use sidewinding to ascend sandy slopes, allowing them to ascend up to the maximum possible sand slope without slip. These snakes are generally lead a solitary life but may gather in groups during hibernation or denning; hibernation takes place in the burrows of rodents or desert tortoises. Newborn sidewinders have unique homeothermy (thermoregulation) behavior that has not been observed in any other type of snake. Following birth, the neonates mass together in their natal burrow. For the first week or so of their lives, newborns literally plug the entrance to this burrow during daylight hours, forming a dynamic multiple-individual mass that takes advantage of the hot exterior environment and the cool interior of the burrow to maintain an average aggregate temperature of 32 °C (the optimal temperature for shedding). The dynamic mass and constant movements of neonates modifies the thermal environment at the burrow entrance such that the young can occupy a location that would ordinarily become lethally hot for an individual neonate (or even an adult).
Sidewinders are polygynous, where males mate with multiple females. They mate in April through May and sometimes in fall. Females give birth to 5-18 live young in late summer to early fall after the gestation period that lasts around 4-5 months. The young are born 15-20 cm (6-8 inches) long. Within a few minutes of being born, the baby sidewinder escapes from a thin, transparent membrane. The young stay at their natal burrow for 7-10 days until they shed; during this time, the mother guards and protects them from predators. After that, the young disperse and have no future contact with their mother or their litter mates. Sidewinders usually mature at two to three years of age.
There are no major threats to sidewinders at present.
According to IUCN, the sidewinder is locally common and widespread throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.