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 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.

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.

Subspecies

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Behavior

thumb|right|150px|Sidewinder tracks in [[Death Valley National Park, showing typical J-shaped impressions]]

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.

The species is nocturnal during hot months and diurnal during the cooler months of its activity period, which is roughly from November to March (probably longer in the southern part of its range).

Juveniles use their tails to attract lizard prey, a behavior termed "caudal luring". Adults lose this behavior as they make the transition from lizard prey to their primary diet of desert rodents, birds, and other snakes. Sidewinder juveniles appear to mimic both life stages of lepidopterans in their luring motions. Their fast luring motions resemble the fluttering of a moth, and their slower tail movements resemble a caterpillar. Both movements have been observed to attract prey lizards.

Neonatal sidewinders engage in a remarkable behavioral homeothermy that has not been observed in any other species of snake. Following birth, the neonates mass together in their natal burrow. Most often, gravid females select an east-facing, small-diameter rodent burrow for giving birth. For the first week or so of their lives, neonatal sidewinders 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&nbsp;°C (the optimal temperature for shedding). The dynamic mass 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). 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, Brown (1973) gives a venom yield of 33&nbsp;mg (Klauber, 1956) and values for mice of 2.6&nbsp;mg/kg IV, 3.0, 4.0, 2.3&nbsp;mg/kg IP and 5.5&nbsp;mg/kg SC for toxicity. With these figures, Brown calculated that the LD<sub>50</sub> for an adult human being weighing 70&nbsp;kg would be 385&nbsp;mg (SC).

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.

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.

The sidewinder was the inspiration for the AIM-9 Sidewinder's name, as both use infrared emanations to track their target.

References

Further reading

  • xiv + 727 pp. + Plates I–XXV. (Crotalus cerastes, p. 583).
  • xi + 378 pp. (Crotalus cerastes, pp. 129, 154).
  • Hallowell, E. (1854). "Descriptions of new Reptiles from California". Proceedings of the Academy of Natural Sciences of Philadelphia 7: 91–97. (Crotalus cerastes, new species, pp. 95–96).
  • (Crotalus cerastes laterorepens, new subspecies, p. 94).
  • A volume of the Humanizing Science Series edited by Jaques Cattell. 185 pp. (Crotalus cerastes, pp. 106–107, 181).
  • (Crotalus cerastes cercobombus, new species).
  • 365 pp., 103 figures + Plates 1–34. (Crotalus cerastes, pp. 300–301, figure 99 + Plate 33).
  • 240 pp. (Crotalus cerastes, pp. 206–207).
  • xiii + 533 pp., 56 color plates. (Crotalus cerastes, p. 113 + Plate 51 + Map 191).
  • 125 pp. (Crotalus cerastes, p. 108).
  • 160 pp. (Crotalus cerastes, pp. 111, 113, 157).
  • Crotalus cerastes cerastes at California Reptiles and Amphibians. Accessed 5 February 2007.
  • Crotalus cerastes at WildHerps. Accessed 5 February 2007.
  • The Sidewinder at VenomousReptiles.org. Accessed 5 February 2007.
  • Mojave Desert Sidewinder at Bird and Hike . com. Accessed 5 February 2007.