SPECIES NAMECrotalus1 ruber2
SUBSPECIESRed-Diamond Rattlesnake Crotalus ruber ruber
FAMILYViperidae (vipers), Subfamily Crotalinae (pit vipers)
REGULATORY STATUSCDFW Species of Special Concern3
U.S. Forest Service – Sensitive4
CALIFORNIA RANGEPeninsular Ranges of Southwestern California
RISK TO HUMANSDangerous/Highly venomous
VENOM CATEGORYHemotoxic, Ruberlysin/Hemorrhagic Toxin II
1. Crotalus, Greek krótalοn meaning “rattle” or “castanet” referring to the rattle on the end of the tail.
2. Ruber, Latin = red, referring to the reddish ground color often exhibited by members of the species.
3. California Department of Fish and Wildlife – Species of Special Concern. A designation to denote declining population levels, limited ranges, and/or continuing threats have made them vulnerable to extinction.
4. U.S. Forest Service – Sensitive. Defined as sensitive species as plant and animal species identified by a regional forester that are not listed or proposed for listing under the federal Endangered Species Act for which population viability is a concern, as evidenced by significant current or predicted downward trends in population numbers or density, or significant current or predicted downward trends in habitat capability that would reduce a species’ existing distribution.
A long, heavy- bodied pit viper with keeled scales, elliptical eyes, spade-shaped head, infrared pits on either side of the head between their eye and nostril, and a distinctive rattle at the tip of its tail. A dark stripe extends from the bottom edge of the eye to the corner of the mouth. Coloration varies from pink, light tan and tones of brown and includes shades of reddish, chestnut, yellow, olive or grey. Red or dark red diamond shaped or longitudinal ovals with light colored edged blotches mark the dorsal with the tail ringed with white and black, with a black ring proximal to a rattle. Ventral coloration is dull yellow or unmarked. Young are duller in color. Adult range from 30-65 inches in length. Males are generally larger than females.
Restricted to the Peninsular Ranges of southwestern California. Inhabits arid scrub, coastal chaparral, oak and pine woodlands, rocky grasslands, mesquite-cactus, and cultivated areas. Most commonly found in mountain foothills and dry rocky desert flats. Prefers densely vegetated or rocky areas, retreating to rock outcroppings, burrows and other subterranean areas for cover and brumation (the process in reptiles of metabolic slowing to conserve energy similar to hibernation in mammals). At risk due to habitat loss in coastal regions.
Specializes in small mammals such as rabbits, ground squirrels, woodrats, and mice. Secondary prey includes birds, lizards, and occasionally other snakes. Capable of climbing small bushes and cacti to reach arboreal birds and mammals. Primarily an ambush hunter, species waits along areas trafficked by prey where it strikes, releases and then tracks the prey following the scent using the vomeronasal organ. Envenomated prey is then consumed whole. Known to occasionally eat carrion. Feeding frequency is approximately every 2 weeks. Most actively hunts nocturnally from April to June, with diurnal hunting during the mild temperatures of spring and late summer.
Typically unaggressive and reclusive. Will remain motionless or move away from threats, but may rattle and strike if provoked or startled. Defensive behavior comprises hissing by inflating the body, posturing or flattening and coiling of the body, raising the forefront off the ground in an S-shape, and keeping the tail raised and rattling which can precede striking. Primarily nocturnal or crepuscular during warmer months between April and October, but may be active during the daytime in cooler spring and late summer months, varying with local environmental conditions. Seeks shade during the heat of the day, under rock outcropping, dense chaparral, cacti patches, brushy bouldered areas and rock crevasses. Have been reported partially climbing easily accessible shrubs and trees for thermoregulation or hunting. Males will engage in combat dancing during mating season, entwining bodies until the weaker male retreats, lasting up to 15 minutes.
Mating occurs in the spring between March and May after a short period of hunting soon after exiting overwintering dens. Sexually mature at 2 years, males will seek females, expanding the home range during mating season. Following a courtship, copulation will last from 6-12 hours. Females give birth to 3-20 live young between July and September after an approximate 165 day gestation period. An ovoviviparous species requires considerable energy from the female, fertilized eggs are retained and prior to birth the young pierce the egg membranes and are born live. Neonates measure 10-12 inches at birth and are born with a single button at the end of the tail that doesn’t produce the rattle sound until additional segments are added during successive shedding. Neonates are duller and greyer in color than adults. They leave the female within hours of birth.
Venom is primarily hemotoxic with characteristic ruberlysin and hemorrhagic toxic II enzymes specific to the species. Venom toxicity increases 6 to 15 times upon maturation. Venom is considered to be less toxic than other rattlesnakes but with the capability of delivering large quantities upon envenomation. Venom consists of proteolytic hemorrhagins. Hemorrhagic effects cause persistent bleeding. Hemotoxins destroy red blood cells and target the circulatory system by interfering with blood pressure, platelets and clotting factors. Antivenin treatment may require multiple doses over several days to neutralize the venom, which may cause permanent damage and disfigurement even when administered shortly after envenomation.
Imperial, Los Angeles*, Orange, Riverside, San Bernardino*, and San Diego counties.
*Indicates counties where the species’ range extends only into a minor portion of the county.