Basilisk Rattlesnake

Crotalus basiliscus, known as the Mexican west coast rattlesnake, Mexican green rattler, and also by other names, is a species of pit viper in the family Viperidae. The species is endemic to western Mexico. Like all other pit vipers, it is venomous. The specific name, basiliscus, is derived from the Greek word for king, βασιλισκος (basiliskos), and alludes to this snake's large size and potent venom. No subspecies are currently recognized.

Description

C. basiliscus is one of the largest rattlesnake species. Specimens exceeding 150 cm (4.9 ft) are not uncommon, while the maximum size reported is 204.5 cm (6.71 ft) (Klauber, 1972). The body is moderately stout and rather rectangular in cross section. Female rattlesnakes of the species are mature at a minimum length of 100 cm (3.3 ft) and a weight of 700 g (1.5 lb).

At midbody, 25-29 rows of strongly keeled dorsal scales occur. The ventral scales number 174-206 and the subcaudals 18-36.

The color pattern consists of brown or grayish ground color overlaid with 26-41 dark, rhombus-shaped (diamond) blotches with light edges. The head is a uniform grayish-brown except for its lighter labial scales and dark postorbital bar. No distinct pattern is found on the crown or neck areas. The tail may be gray, with darker bands, or almost uniform in color without any distinct markings. The belly is white or cream-colored. The young are mostly red, but adults eventually become an olive green. Within its range, this is the only rattlesnake with diamond-shaped dorsal markings.

This snake often occurs in the same areas as C. molossus, where the two appear to hybridize freely. While these two species are easily distinguished, identifying the hybrid specimens is problematic.

Common names

Common names for C. basiliscus include Mexican west coast rattlesnake, Mexican green rattler, Mexican west coast green rattlesnake, and in Spanish cascabel verde mexicana.

Geographic range

This rattler, C. basiliscus, is found in western Mexico from southern Sonora to Michoacán, where it is mostly restricted to the coastal plain. The type locality given is "Near Colima, Mexico".

Habitat

Around Colima, where C. basiliscus is (or was at one point) particularly plentiful, the area has been described as mostly treeless and covered with short grass with scattered clumps of mesquite, acacias, and other thorny bushes, as well as plenty of large cacti. The habitat of C. basiliscus is mostly tropical thorn forest, with an extension into tropical deciduous forest.

Conservation status

The species C. basiliscus 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 trend for this species was stable when assessed in 2007.

Behavior