San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide
San Esteban Island Rattlesnake, photographed by BDH

Crotalus estebanensis
San Esteban Island Rattlesnake


Crotalus comes from the Greek crotalon, meaning a rattle or little bell; estebanensis is a latinized spelling of the island San Esteban in the Gulf of California. For a long period of time, this species was recognized as a subspecies of Crotalus molossus. In Spanish, rattlesnakes are known as La Vibora de Cascabel.


The San Esteban Island Rattlesnake is a derivative of the Black-tailed Rattlesnake. It can grow to lengths of slightly less than 3 feet (1 m). The body is moderately built. Its coloration varies from olive-green to yellowish. The anterior dorsal blotches are not distinct but become better formed along the midbody. The tail is black with a distinctive rattle.

Range and Habitat

The San Esteban Island Black-tailed Rattlesnake can only be found on San Esteban Island located in the Gulf of California. The island's habitat is composed of Central Gulf Coast Desert plants. It is often found along the margins of the large arroyo which opens to the southeast side of the island.

Natural History

Little is known about the natural history of this island endemic. It is known to occur throughout Isla San Esteban. It is slightly smaller in size than its closest Black-tailed Rattlesnake relatives. The rattle has been described as degenerate, as if it is in the process of losing it through evolutionary selection. However, these claims are exaggerated. The rattle is well-formed, fully functional, although proportionately smaller than its mainland relatives.

Conservation Status

Because this species only occurs on a single island, it is susceptible to extinction by collecting and the introduction of exotic predators such as feral cats. There have been no proposed conservation plans. Because of widespread negative attitudes towards snakes, very few conservation programs, worldwide, have been created. A much higher percentage of snakes are threatened with extinction than is currently recognized. Therefore, snakes are particularly susceptible to being overlooked by conservation-minded biologists.

Text by David Gonzalez and Bradford Hollingsworth.
Photos by Bradford Hollingsworth.

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