San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide
Western Rattlesnake, San Diego County, photographed by Bradford Hollingsworth

Crotalus viridis
Western Rattlesnake

VIPERIDAE

Crotalus comes from the Greek crotalon, a rattle or little bell; viridis is Latin for green.

Description

Size: The Western Rattlesnake can reach lengths slightly over 4 feet, but 2 1/2 feet is more the norm.

Coloration: The Western Rattlesnake (Crotalus viridis) is a widely distributed and highly variable species. In our region, this snake is lighter gray or brown. Pale margins edge the pattern of its dark dorsal blotches. In some individuals, the pale margins can be yellow, giving the snake a greenish cast. Specimens from high elevations can be a velvety, jet black with only a slight hint of patterning. A light stripe runs from outside corner of the eye to the corner of the mouth, and the tail has dark rings. Juveniles have a yellowish tail, and their dorsal patterning contrasts more than that in adults.

s Subspecies: There are as many as nine subspecies. Only the Southern Pacific Rattlesnake (C. v. helleri) and the Los Coronados Island Rattlesnake (C. v. caliginis) occur in our region.

Range and Habitat

The Western Rattlesnake is distributed across most of the western United States, Mexico, and Canada. The Southern Pacific Rattlesnake (C. v. helleri) is distributed from southern California to the central part of the Baja California. The Los Coronados Island Rattlesnake (C. v. caliginis) is found only on the southern island of the Coronados Islands, off the Pacific coast of northern Baja California.

In southern California, this species is cismontane and is not found on the eastern slopes of the mountains. The Western Rattlesnake enjoys a wide range of habitats from seacoast to pine wooded mountain heights, and is tolerant of disturbed areas. It is the most abundant rattler of our region, west of the desert.

Natural History

Behavior: In early spring, the Western Rattlesnake basks in the sun or glides around as it looks for food and mates. In dense chaparral, where little sun reaches the ground, it may climb to the tops of bushes to bask. As the weather warms, it becomes more active at dusk or at night.

Prey and Predators: Their diet includes small mammals, birds, reptiles and amphibians.

Breeding: A female may bear 4 to 12 young in late summer.

Conservation Status

There has been no proposed conservation status. 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 suspectible to being overlooked by conservation-minded biologists.


Contributed by Jim Melli. Photo by Bradford Hollingsworth

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