San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide
San Lorenzo Island Rattlesnake,and rattleless tail, photographed by BDH

Crotalus lorenzoensis
San Lorenzo Island Rattlesnake


Crotalus comes from the Greek crotalon, meaning a rattle or little bell. The name lorenzoensis is a latinized spelling for the island San Lorenzo Sur. For a long period of time, this species was recognized as a subspecies of Crotalus exsul. In Spanish, rattlesnakes are known as La Vibora de Cascabel.


The San Lorenzo Island Rattlesnake grows up to be fairly large, measuring slightly less then 3 feet (1 m). It is reddish-brown or brick red in color with diamond markings with white highlights running down its back. A thick reddish-brown stripe runs behind the eye, towards the upper labial scales of the mouth. The tail has narrow black and broad white bands. This species is similar to the Santa Catalina Island Rattlesnake because it also has a degenerate rattle button, although the rattle doesn't always fall off as it is formed.

Range and Habitat

This species can only be found on San Lorenzo Sur Island located in the Gulf of California. The island's habitat is composed of Central Gulf Coast Desert plants. This rattlesnake if often found in the bottoms of the arroyos which cut into the steep backbone of the island.

Natural History

Little is known about the natural history of this island endemic. It is nocturnal and most likely feeds on rodents. Similar to the Santa Catalina Island Rattlesnake, this species will also climb into the scrub vegetation. In one instance, an individual encountered at night retreated into a bush and climbed 6 feet to coil in the fork of a branch. The rattleless condition occurs in about half of the individuals on the island.

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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