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

Crotalus catalinensis
Santa Catalina Island Rattlesnake

VIPERIDAE

Crotalus comes from the Greek crotalon, meaning a rattle or little bell; catalinensis is a latinized spelling of the island Santa Catalina in the Gulf of California. In Spanish, rattlesnakes are known as La Vibora de Cascabel.

Description

The Santa Catalina Island Rattlesnake is a medium sized, slender snake, growing to a little over 2 feet in length. This particular rattler has two distinct color variations; the commonly seen one is light brown or reddish brown with darker diamond shaped blotches. Each diamond has a dark border and an outline consisting of light colored scales. The other color morph is ash-grey with darker grey markings. On the head, there are pale stripes running through the center of the supraocular scales. Ironicaly, the most distinctive feature of this rattler is the lack of the rattle. The base of the rattle (referred to as the button) is degenerate, so the rattle segment falls off as it is formed.

Range and Habitat

The Santa Catalina Island Rattlesnake can only be found on Isla Santa Catalina located in the Gulf of California of the southern portion of the Baja California peninsula. The island's habitat is composed of Gulf Coast Desert plants. It is often found within the many arroyos on the western side of the island.

Natural History

The rattleless tail of a Santa Catalina Island Rattlesnake, photographed by BDH
The rattleless tail of a Santa Catalina Island Rattlesnake. Photography by Bradford Hollingsworth.

Little is known about the natural history of this island endemic. It is known to occur mostly within the arroyo bottoms. This species is often referred to as the Santa Catalina Island Rattleless Rattlesnake. In most rattlesnakes, the rattle is normally formed in segments. The first segment is attached to the base of the tail and additional segments are added when the snake sheds its skin. The degenerate nature of the rattle button in the Santa Catalina Island Rattlesnake causes the rattle segments to fall off after each shed.

It is thought that the secondary loss of the rattle is an evolutionary adaptation for hunting birds. This species has arboreal tendencies and can often be found a few feet off the ground climbing through the desert brush on the island. A fully developed rattle would make a considerable amount of noise as the snake climbed through the brush, which would scare off roosting birds. This species will often hang onto its prey, unlike most rattlesnakes. It is thought this behavioral modification is associated with the problems of tracking a bird after a bite is delivered.

The Santa Catalina Island Rattlesnake can move quickly through the branches and is unlike the large, heavy-bodied, terrestrial rattlesnake species.

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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