Sidewinder

Crotalus cerastes, also known commonly as the horned rattlesnake, the sidewinder, and the sidewinder rattlesnake, is a species of pit viper, a venomous snake in the subfamily Crotalinae of the family Viperidae. The species is native to desert regions of the Southwestern United States and adjacent northwestern Mexico. Three subspecies are recognized as being valid.

Description

A small species, adult specimens of Crotalus cerastes measure between 43 and 80 cm (17 and 31.5 in) in total length (tail included). The females are larger than the males, which is unique among United States rattlesnakes.

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. As only pressure on top of the horns will cause them to fold down, it is concluded that they strike against the roof of rodent burrows to protect the eyes.

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. Klauber and Neill describe the ability of this species to display different coloration depending on the temperature—a process known as metachrosis.

Common names

Common names for Crotalus cerastes include horned rattlesnake, sidewinder, sidewinder rattlesnake, and Mojave Desert sidewinder (for C. c. cerastes),

Subspecies

Geographic distribution and habitat

In the Southwestern United States, Crotalus cerastes 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.

Conservation status

The species Crotalus cerastes is classified as least concern on the IUCN Red List (v3.1, 2001). Species are listed as such due to their wide distribution, presumed large population, or because they are unlikely to be declining fast enough to qualify for listing in a more threatened category. The population trend was stable when assessed in 2007.

Behavior

The common name sidewinder alludes to its unusual form of locomotion, which is thought to give it traction on windblown desert sand, but this peculiar locomotor specialization is used on any substrate over which the sidewinder can move rapidly. As its body progresses over loose sand, it forms a letter J-shaped impression, with the tip of the hook pointing in the direction of travel. Sidewinding is also the primary mode of locomotion in other desert sand dwellers, such as the horned adder (Bitis caudalis) and Peringuey's adder (Bitis peringueyi), but many other snakes can assume this form of locomotion when on slick substrates (e.g., mud flats). The sidewinder rattlesnake can use sidewinding to ascend sandy slopes by increasing the portion of the body in contact with the sand to match the reduced yielding force of the inclined sand, allowing it to ascend up to the maximum possible sand slope without slip. In cybernetics, incorporating this control scheme into a snakebot can enable the robot to replicate sidewinding movement. Activity range does not change with sex or body size.