
Generally, this species does not exceed 100 cm in length, with large males measuring between 90 and 100 cm. The race on Angel de la Guarda Island is known to become larger, the maximum recorded length for a specimen there being 136.7 cm. In contrast, the population on El Muerto Island only reaches a maximum of 63.7 cm in length
Found in the southwestern United States and in northwestern Mexico. In the United States, its range includes east-central and southern California, southwestern Nevada, extreme southwestern Utah and western Arizona. In Mexico it is native in most of Baja California, including Baja California Sur. It also inhabits a number of islands in the Gulf of California, including Angel de la Guarda, Carmen, Cerralvo, El Muerto, Espíritu Santo, Monserrate, Piojo, Salsipuedes, San José, as well as on Santa Margarita Island off the Pacific coast of Baja California Sur
Like many other snakes, this species tends to be diurnal in cool weather, and nocturnal during hot weather. Speckled rattlers are alert and often quick to rattle when disturbed. Prey consists of small mammals, lizards, and occasionally birds. Mating occurs in spring, and 3 to 11 live young are born in late summer.
This species is classified as Least Concern (LC) on the IUCN Red List of Threatened Species (v3.1, 2001). 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
| Subspecies | Common name | Geographic range |
|---|---|---|
C. m. angelensis |
Angel de la Guarda Island speckled rattlesnake |
Mexico, on the island of Ángel de la Guarda. |
C. m. mitchellii |
San Lucan speckled rattlesnake |
Mexico, in Baja California Sur and on the islands of Santa Margarita, Cerralvo, Espíritu Santo, San José, Monserrate and Carmen. |
C. m. muertensis |
El Muerto Island speckled rattlesnake |
Mexico, on the island of El Muerto. |
C. m. pyrrhus |
Southwestern speckled rattlesnake |
The United States in southern California, southern Nevada, southwestern Utah and western Arizona. Mexico in northwestern Sonora and northern Baja California. |
C. m. stephensi |
Panamint rattlesnake |
The United States in east-central California and southwestern Nevada. |