Crotalus cerastes

Common names: sidewinder, horned rattlesnake, sidewinder rattlesnake,^[2] more.

Crotalus cerastes is a venomous pitviper species found in the desert regions of the southwestern United States and northwestern Mexico. Three subspecies are currently recognized, including the nominate subspecies described here.^[3]

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Description

A small species, with adult specimens measuring between 43 cm and 76 cm in length.^[2] According to Campbell and Lamar (2004), most adults are 50-80 cm in length.^[4] The females are larger than the males, which is unusual for this group of snakes.^[5]

Midbody there are usually 21 rows of keeled dorsal scales.^[2][6] In males there 141 ventral scales or less; in females 144 or less.^[2] 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 the sand.^[5]

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 that are subrhombic or subelliptical.^[4] 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.^[2]

Common names

Sidewinder, horned rattlesnake, sidewinder rattlesnake, Mojave Desert sidewinder (for C. c. cerastes),^[2] sidewinder rattler.^[7]

Geographic range

In the southwestern United States this species is found in the desert region of eastern California, southern Nevada, extreme southwestern Utah and western Arizona. In northwestern Mexico it is found in western Sonora and eastern Baja California. The type locality is listed as the "borders of the Mohave river, and in the desert of the Mohave" (California).^[1]

Conservation status

This species is classified as Least Concern (LC) on the IUCN Red List of Threatened Species (v3.1, 2001).^[8] Species are listed as such due to their wide distribution, presumed large population, or because it is unlikely to be declining fast enough to qualify for listing in a more threatened category. The population trend is stable. Year assessed: 2007.^[9]

Behavior

  The common name sidewinder is an allusion 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 that the sidewinder can move over 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 species is nocturnal during hot months and diurnal during the cooler months of its activity period, which is roughly from March to November (probably longer in the southern part of its range).

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 out of 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, it is thought that the mother guards and protects them from predators.

Juvenile Sidewinders use their tails to attract lizard prey (see video: [1]), a behavior termed "caudal luring." Adult Sidewinders lose this behavior as they make the transition from lizard prey to their primary diet of desert rodents.

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 cousins. Still, any bite should be taken seriously and medical attention sought immediately.

Norris (2004) lists the following venom yields: 33 mg average and 63 mg maximum (Klauber, 1956), and 30 mg average and 80 mg maximum (Glenn & Straight, 1982).^[10] Brown (1973) gives a venom yield of 33 mg (Klauber, 1956) and LD₅₀ values for mice of 2.6 mg/kg IV, 3.0, 4.0, 2.3 mg/kg IP and 5.5 mg/kg SC for toxicity. With these figures, Brown calculated that the LD₅₀ for an adult human being weighing 70 kg would be 385 mg (SC).^[11]

Bites can cause pain, swelling, hemorrhagic bleb formation and ecchymosis. Any swelling is usually not particularly severe, but it can involve all of the affected limb as well as the trunk. Systemic symptoms can include nausea, dizziness, chills, coagulopathy and shock.^[10] Klauber (1997) includes 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 itself was described as no more painful than a pin prick, a doctor was seen within about 25 minutes and 10 cc of antivenin had been administered, within 2.5 hours his entire arm had swelled and the pain was violent, "as if the arm were soaked in a bucket of boiling oil."^[12]

Subspecies

See also

• List of crotaline species and subspecies
• Crotalus by common name
• Crotalus by taxonomic synonyms
• Crotalinae by common name
• Crotalinae by taxonomic synonyms
• Snakebite

References