Description: This moderately large species commonly exceeds 39 inches on the mainland. Large males may exceed 55 inches, although specimens of over 59 inches are quite rare. The largest specimen on record measured 64 inches. Crotalus ruber is very similar in pattern to C. atrox, but it is distinguished by its reddish color, to which the specific name, ruber, refers. Also, the first lower labial scale on each side is transversely divided to form a pair of anterior chin shields. The dorsal scales are usually arranged in 29 rows, but may vary from 25 to 31 rows. Ventrals range from 185 to 206. Snakes found in coastal regions are longer on average than those found in desert regions.

Habitat: C. ruber inhabits the cooler coastal zone, over the mountains, and into the desert beyond. It prefers the dense chaparral country of the foothills, cactus patches, and boulders covered with brush, from sea level to 1,500 m in altitude.

Range: Red diamond rattlesnakes are found in the United States in southwestern California and southward through the Baja California peninsula, although not in the desert east of the Sierra de Juárez in northeastern Baja California. It also inhabits a number of islands in the Gulf of California, including Angel de la Guarda, Pond, San Lorenzo del Sur, San Marcos, Danzante, Monserrate and San José. Off the west coast of Baja California, it is found on Isla de Santa Margarita, which is off Baja California Sur, and (as C. exsul) on Isla de Cedros.

Found in these States: CA

Venom: This species is of a mild disposition and has one of the least potent rattlesnake venoms. Nonetheless, a bite from this species is still a medical emergency and can be fatal without prompt antivenom treatment. An average venom yield of 364 mg (dried) and LD50 values of 4.0, 3.7 mg/kg IV, 6.0, 7.0, 6.7 mg/kg IP and 21.2 mg/kg SC for toxicity. However, Norris warned this species has a relatively large venom yield containing high levels of proteolytic enzymes, especially in the adults. A publication he mentions by Rael et al. (1986) showed it contains at least three proteolytic hemorrhagins that degrade fibrinogen and cause myonecrosis, but no Mojave toxin. On the other hand, three specimens from Mexico studied by Glen et al. did have Mojave toxin and lacked hemorrhagic activity. Bite symptoms include massive tissue swelling, pain, ecchymosis, hemorrhagic blebs, and necrosis. Systemic symptoms may include nausea, vomiting, coagulopathy, clinical bleeding and hemolysis.

Diet: This species preys on rabbits, ground squirrels, birds, lizards, and other snakes. Snakes from coastal populations consume prey of larger body mass than snakes from desert populations.

Reproduction: Mating occurs between February and April. Females give birth in August, to between three and 20 young. Neonates are 30 to 34 cm in length.

Status: This species is classified as Least Concern on the IUCN Red List of Threatened Species. Species are listed as such due to their wide distribution, presumed large population, or because they are unlikely to be declining fast enough to qualify for listing in a more threatened category. The population trend was down when assessed in 2007.

Subspecies: Three, with just 1 found in the United States:
   Cedros Island Red Diamond Rattlesnake - (Crotalus ruber exsul)
   San Lucan Red Diamond Rattlesnake - (Crotalus ruber lucasensis)
   Red Diamond Rattlesnake - (Crotalus ruber ruber)

Taxonomy: