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

Crotalus molossus
Black-tailed Rattlesnake


Crotalus comes from the Greek crotalon, meaning a rattle or little bell. The name molossus comes from Greek molossos, which refers to the the Molossos Hound. It's uncertain whether the name molossus indicates that this snake shares any characteristics with this breed of dog. In Spanish, rattlesnakes are known as La Vibora de Cascabel.


The Black-tailed Rattlesnake reaches lengths from 28-49 inches (71-126 cm). The dorsal coloration varies from greenish, yellowish, grayish, or olive, with black or brown crossbands or blotches of irregular outline. It has a distinctive black tail. Black is also found on the snout.

Range and Habitat

The Black-tailed Rattlesnake ranges from central Texas through western Arizona, and southward to the edge of the Mexican Plateau. In our region, it is found on Isla Tiburón in the Gulf of California. This island is located along the coast of central Sonora in mainland México.

This snake is an ecological generalist and can be found in a wide variety of habitats. It can occur in mountainous terrain with rocky outcrops or wooded canyons. It is most frequently found near rocky habitats. It is also found within arroyos in the desert. It is found from sea level to around 9600 feet (3150 m). It appears to avoids grasslands and barren desert.

Natural History

Behavior:This species is known to be a mild-mannered snake which will quickly retreat if encountered in the field. Through radiotelemetry studies, it has been found that females will protect their new born babies until their first shed. Maternal care is thought to be rare in snakes, although this may simply represent our lack of understanding of these animal's secretive behavior.

Diet:The Black-tailed Rattlesnake will eat a wide variety of vertebrate animals including pocket mice, woodrats, squirrels, rabbits, chipmunks, and birds. Juveniles are also known to eat lizards.

Breeding: This snake is viviparous, having 3-16 live young, 9-12 inches long. The babies are born during the summer months from July to August.

Conservation Status

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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