Adult, crawling on boulder at night,
San Diego County desert
Adult, crossing a popular hiking trail in coastal San Diego County in the middle of the afternoon, managing
to avoid observation by all visitors except myself. You can see the tracks it made in the sand on the right.
Habitat, Riverside County
riparian desert foothills
Habitat, coastal San Diego County
Short Videos and Sound
A large old Red Diamond Rattlesnake rattles on top of a boulder in coastal San Diego County.
A close view of a rattling Red Diamond Rattlesnake's tail.
A large adult Red Diamond Rattlesnake crawls up some large boulders at the edge of a desert wash in San Diego County. After trying to climb up past the top of the boulder, it crawled back down. Despite the bright lights, it did not appear to notice me and continued its nocturnal wandering.
A Red Diamond Rattlesnake crawls across the hot sand at mid day in San Diego County, then takes shelter between some rocks.
A Red Diamond Rattlesnake found on a desert road at night.
Listen to a rattlesnake rattling.
California State Park warning sign.
Click the picture to see more rattlesnake signs.
Rattlesnakes are important members of the natural community. They will not attack, but if disturbed or cornered, they will defend themselves. Reasonable watchfulness should be sufficient to avoid snakebite. Give them distance and respect.
"Rattlesnakes are also among the most reasonable forms of dangerous wildlife: their first line of defense is to remain motionless; if you surprise them or cut off their retreat, they offer an audio warning; if you get too close, they head for cover. Venom is intended for prey so they're reluctant to bite, and 25 to 50 percent of all bites are dry - no venom is injected."Leslie Anthony. Snakebit: Confessions of a Herpetologist. Greystone Books, 2008.
Rattlesnakes are the only kind of native California snakes that we typically refer to as poisonous, but actually, they are not poisonous they are venomous. A poisonous snake is one that is harmful to eat. A venomous snake injects dangerous venom into its victim.
Rattlesnake bites can be extremely dangerous, but rattlesnakes should not be characterized as agressive and vicious, striking and biting without provocation, as they are often shown in movies and TV shows. If rattlesnakes are given some space and some time to escape to a safe place, they will usually just crawl away as fast as possible and avoid confrontation. Rattlesnakes will not strike without a reason: they will strike at a potential meal and they will defend themselves from anything they perceive as dangerous. They avoid striking and biting because it uses up their valuable supply of venom which they need to kill and digest their food. Rattlesnakes are often portrayed with the body partly coiled, the tail rattling loudly, and the head raised up and ready to strike, but they do not need to coil this way to strike. This display is a warning not to come any closer. It's a defensive behavior that some rattlesnakes use when they sense that crawling away would put them in danger of attack.
Rattlesnaks do not always rattle. Often they will rattle loudly to warn potential enemies of their presence but they will often remain silent when they sense a threat, using their cryptic color and pattern to blend into their surroundings to hide from the threat. In this situation making noise risks advertising their presence. They also use their natural camouflage to hunt by sitting still and not rattling, trying to remain invisible as they wait for a warm-blooded prey animal to pass close enough for the snake to strike it.
Dangerously Venomous(Commonly but inaccurately called "Poisonous.")
A bite from this snake can be very dangerous without immediate medical treatment. Treatment can require hospitalization and great expense.
Adults are 30 - 65 inches in length ( 76 - 165 cm) typically 2 - 4.5 feet long.
Young are about 12 inches long.
A long, heavy-bodied pit viper, with a thin neck, a large triangular head, and a rattle on the end of the tail consisting of loose interlocking hollow segments.
Pupils are elliptical.
Scales are keeled.
Has two pits, one on each side of the front of the head above the mouth that are used to sense heat when hunting warm-blooded prey.
Color and Pattern
Variable in ground color; pink, reddish-tan, reddish-brown or brick red.
Diamond-shaped blotches, usually with light edges, mark the back.
The underside is usually dull yellow and unmarked.
Black and white rings surround a thick tail.
(Unlike most snake species, males of this species tend to be larger in body length than females.)
Juveniles are duller in coloring than adults.
Newborn snakes do not have a rattle - just a single button which does not make a sound.
Comparethe Western Diamond-backed Rattlesnake to the Red Diamond Rattlesnake
Life History and Behavior
Primarily nocturnal and crepuscular during periods of excessive daytime heat, but also active during daylight when the temperature is more moderate or when in the comparatively cooler shaded areas of boulder fields.
Not active during cooler periods in Winter.
Terrestrial, but may partially climb shrubs or trees.
Fangs and Venom
Rattlesnakes have long, hollow, movable fangs connected to venom glands. The fangs are replaced if broken. A snakes uses its fangs to inject a toxic venom which quickly immobilize its prey. A rattlesnake can control the amount of venom injected.
Bites that inject venom into humans are potentially dangerous without immediate medical treatment.
Sometimes a rattlesnake bites but does not inject venom. These are called "dry bites." A dry bite may still require medical attention.
Even a dead snake can bite and inject venom if the jaws open reflexively when they are touched.
Sound - The Rattle
When alarmed, a rattlesnake shakes its tail back and forth. The movement rubs the rattle segments together producing a buzzing sound which serves as a warning. Juveniles are born with only a silent button at the end of the tail.
A new rattle segment is added each time the skin is shed, which can be more than one time per year.
Diet and Feeding
Eats small mammals, including ground squirrels, wood rats, and rabbits, lizards, and birds.
Prey is found when actively moving, or by ambush, where the snake waits near lizard or rodent trails, striking at and releasing passing prey.
The snake then follows the trail of the envenomated animal and swallows it whole.
Pits on the sides of the head sense heat. These heat sensors help the snake to locate prey by their warmth.
Long, hollow, movable fangs connected to venom glands inject a very toxic venom which quickly immobilizes the prey.
The snake can control the amount of venom injected and the fangs are replaced if broken.
Dugan and Hayes, 2012, found that this species specializes on mammalian prey, with terrestrial rodents the primary prey source. Wood rats were the most abundant prey species, followed by kangaroo rats, pocket mice, and deer mice. Coastal populations average longer in body size and eat a higher proportion of larger rodents than snakes from desert populations.
(Adult California Ground Squirrels are immune to rattlesnake venom and will intensely confront any snake they feel to be a threat.)
Rattlesnakes are ovoviparous. The mother keeps her fertilized eggs inside her body and gives birth to living young.
Breeding typically occurs in the spring. Males search extensively for females during the mating season.
Famales probably start bearing young at three years of age and breed annually. (Klauber, 1982)
Three to 20 young are born July through September. (Stebbins & McGinnis, 2013)
Adult males engage in a ritual "Combat Dance" during the spring breeding season. Necks and forebodies are intertwined, with the stronger snake slamming the smaller one to the ground until the weaker snake leaves the area. "...The presence of a female is not necessary to stimulate the males to dance." (Klauber, 1982)
Inhabits arid scrub, coastal chaparral, oak and pine woodlands, rocky grassland, cultivated areas.
On the desert slopes of the mountains, it ranges into rocky desert flats.
Found in southwestern California, from the Morongo Valley west to the coast and south along the peninsular ranges to mid Baja California.
Notes on Taxonomy
Previously recognized as a subspecies of Crotalus ruber - Crotalus ruber ruber. Some taxonomists regard this snake as a subspecies of Crotalus exsul labelling it Crotalus exsul ruber.
Alternate and Previous Names (Synonyms)
Crotalus ruber - Red Diamond Rattlesnake (Stebbins & McGinnis 2012) Crotalus ruber ruber - Northern Red Rattlesnake (Stebbins 1985, 2003 ) Crotalus ruber ruber - Red Diamond Rattlesnake (Wright & Wright 1957, Stebbins 1966, Klauber 1982) Crotalus ruber - Red Diamond Rattlesnake (Stebbins 1954) Crotalus ruber ruber - Red Diamond Rattlesnake (Grinnell and Camp 1917) Crotalus ruber - Red Rattlesnake (Atsatt 1913) Crotalus ruber (Cope, 1892)
Stebbins, Robert C., and McGinnis, Samuel M. Field Guide to Amphibians and Reptiles of California: Revised Edition (California Natural History Guides) University of California Press, 2012.
Stebbins, Robert C. California Amphibians and Reptiles. The University of California Press, 1972.
Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003.
Behler, John L., and F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992.
Powell, Robert., Joseph T. Collins, and Errol D. Hooper Jr. A Key to Amphibians and Reptiles of the Continental United States and Canada. The University Press of Kansas, 1998.
Bartlett, R. D. & Patricia P. Bartlett. Guide and Reference to the Snakes of Western North America (North of Mexico) and Hawaii. University Press of Florida, 2009.
Bartlett, R. D. & Alan Tennant. Snakes of North America - Western Region. Gulf Publishing Co., 2000.
Brown, Philip R. A Field Guide to Snakes of California. Gulf Publishing Co., 1997.
Ernst, Carl H., Evelyn M. Ernst, & Robert M. Corker. Snakes of the United States and Canada. Smithsonian Institution Press, 2003.
Wright, Albert Hazen & Anna Allen Wright. Handbook of Snakes of the United States and Canada. Cornell University Press, 1957.
Ernst, Carl. H. Venomous Reptiles of North America. Smithsonian Institution Press, 1999.
Hayes, William K., Kent R. Beaman, Michael D. Cardwell, and Sean P. Bush, editors. The Biology of Rattlesnakes. Loma Linda University Press, 2009.
Hubbs, Brian R., & Brendan O'Connor. A Guide to the Rattlesnakes and other Venomous Serpents of the United States. Tricolor Books, 2011.
Klauber, Laurence M. Rattlesnakes. University of California Press. (Abridged from the 1956 two volume Rattlesnakes:
Their Habits, Life Histories, and Influence on Mankind.) University of California Press, 1982.
Rubio, Manny. Rattlesnake - Portrait of a Predator. Smithsonian Institution Press, 1998.
Walls, Jerry G. Rattlesnakes: Their Natural History and Care. T. F. H. Publications, Inc., 1996.
Eric A. Dugan and William K. Hayes. Diet and Feeding Ecology of the Red Diamond Rattlesnake, Crotalus Ruber (Serpentes: Viperidae)
Herpetologica, 68(2), 2012, 203–217 E 2012 by The Herpetologists’ League, Inc.
Eric A. Dugan, Alex Figueroa, and William K. Hayes. Home Range Size, Movements, and Mating Phenology of Sympatric Red Diamond (Crotalus ruber) and Southern Pacific (C. oreganus helleri) Rattlesnakes in Southern California. Pp. 353-364 in W. K. Hayes, K. R. Beaman, M. D. Cardwell, and S. P. Bush (eds.), The Biology of Rattlesnakes. Loma Linda University Press. 2008.
The following status listings are copied from the April 2018 Special Animals List and the 2017 Endangered and Threatened Animals List, both of which are published by the California Department of Fish and Wildlife.
If no status is listed here, the animal is not included on either CDFW list. This most likely indicates that there are no serious conservation concerns for the animal. To find out more about an animal's status, you can go to the NatureServe and IUCN websites to check their rankings.
Check here to see the most current complete lists.
NatureServe Global Ranking
Apparently Secure—Uncommon but not rare; some cause for long-term concern due to declines or other factors.
NatureServe State Ranking
Vulnerable in the state due to a restricted range, relatively few populations (often 80 or fewer), recent and widespread declines, or other factors making it vulnerable to extirpation from the state.