Crotalus tigris

Common names: tiger rattlesnake, tiger rattler.^[2]

Crotalus tigris is a venomous pitviper species found in the southwestern United States and northwestern Mexico. No subspecies are currently recognized.^[3] The specific name is Latin for tiger and is an allusion to many narrow dorsal crossbands that create a pattern of vertical stripes.^[4]

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Description

  A relatively small species with adult reaching less than 100 cm in length. The largest specimen on record measured 88.5 cm (Klauber, 1956). Proportionally, the head is small and the rattle is large.^[4]

The color pattern consists of a gray, lavender, blue-gray, pink or buff ground color that usually turns to pink, pale orange or cream on the sides. This is overlaid with a series of 35-52 crossbands that are dark gray or brown in color and consist mainly of heavy punctations. These crossbands have vague borders and are wider dorsally than latterally. Also middorsally, the crossbands become wider than the spaces that separate them. Posteriorly, the crossbands also become darker and more clearly defined. The markings on the head are mostly vague and irregular, although towards the rear a few dark marking may be arranged as paired occipital blotches and upper temporal streaks. ^[4]

Geographic range

Found in the southwestern United States in south-central Arizona, and in northwestern Mexico in Sonora. Also found on Isla Tiburón in the Gulf of California. The type locality is described as "Sierra Verde and Pozo Verde." The latter is a spring located on the Sonora side of the US-Mexico border, near Sasabe. According to Stejneger (1893), this spring is on the western slope of the southern Sierra Verde, which is also known as the Sierra del Pozo Verde.^[1]

Conservation status

This species is classified as Least Concern (LC) on the IUCN Red List of Threatened Species (v3.1, 2001).^[5] 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.^[6]

Venom

Although it has a comparatively low venom yield, according to Weinstein and Smith (1990) its toxicity is considered to be the highest of all rattlesnake venoms. It has a high neurotoxic fraction that is antigenically related to Mojave toxin (see Crotalus scutulatus, venom A), and includes another component that is immunologically identical to crotamine, which is a myotoxin also found in tropical rattlesnakes (see Crotalus durissus). There is low, but significant protease activity in the venom, although there does not seem to be any hemolytic activity.^[7]

Brown (1973) lists an average venom yield of 11 mg (dried venom) and an LD₅₀ value of 0.6 mg/kg IP for toxicity.^[8]

As far as bite symptoms are concerned, there is essentially no information available. Despite the toxicity of the venom, it would seem to cause little in the way of local or systemic symptoms in humans.^[7]

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