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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.
Rattlesnake bites can be extremely dangerous, but rattlesnakes should not be considered as vicious and always ready to attack without provocation. They will not strike without a reason, but they will aggressively defend themselves. They are often portrayed with the body partly coiled, the tail rattling loudly, and the head up ready to strike. This display is a warning not to come any closer or they will strike; a defensive behavior that some rattlesnakes use when they sense that crawling away would put them in danger. If they are given some space and some time to escape to a safe place, they will usually crawl away as fast as possible.
Because they cannot crawl to safety as fast as some snakes, rattlesnakes often use their cryptic color and pattern to blend into their surroundings in order to hide from their prey and from other animals that could threaten them. They often hunt by sitting still and waiting for a warm-blooded prey animal to pass close enough for the snake to strike it. Sometimes a passing human will be struck instead, mistaken for food. When they sense the presence of something that might threaten them, rattlesnakes often lie still to avoid detection and do not rattle, because that would give away their location. At other times they rattle loudly, sometimes from a good distance, to warn potential enemies of their presence. In both cases they are doing everything they can to avoid confrontation and to avoid striking and biting and using up their valuable supply of venom which they need to kill and digest their food.
A bite by this snake can be very dangerous without immediate medical treatment. Treatment can require hospitalization and great expense.
Adults 30 - 44 inches long, sometimes up to 54 inches. Newborns about 10 inches long.
A 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.
A new rattle segment is added each time the skin is shed, which can be more than one time per year.
Pupils are elliptical.
Scales are keeled.
Color and Pattern
Ground color is brown to olive-brown.
Dark brown blotches, completely outlined by light pigment, mark the back.
These blotches turn to bars toward the tail, which is surrounded with dark rings.
The last tail ring is not well-defined and is more than twice the width of the other rings.
The underside is pale, sometimes weakly mottled.
Young have a bright yellow tail with no rattle - just a single button which does not make a sound.
The pattern is brighter on juveniles than on adults.
Primarily nocturnal and crepuscular during periods of excessive daytime heat, but also active during daylight when the temperature is more moderate. Not active during cooler periods in Winter.
Radiotelemetry studies have shown that the home range of male snakes is larger than that of females.
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.
Diet and Feeding
Eats birds, lizards, snakes, frogs, insects, and small mammals, including mice, rats, rabbits, hares, and ground squirrels. (Adult California Ground Squirrels are immune to rattlesnake venom and will intensely confront any snake they feel to be a threat.)
Prey is found while the snake is 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.
Live-bearing; young are born August - October.
Breeding activity occurs twice per year - in the spring and in late summer/early fall.
Male rattlesnakes search extensively for females during the mating season while females do not actively search for males.
Male to male combat occurs.
Known to hybridize with the Northern Mohave Rattlesnake where their ranges overlap in the Antelope Valley.
This subspecies, Crotalus oreganus helleri - Southern Pacific Rattlesnake, is found in California from Santa Barbara County, where there is a wide zone of intergradation with the Northern Pacific Rattlesnake north to around Morro Bay, east to the central valley and the desert slopes of the transverse and peninsular ranges, and south into the middle of the Baja California peninsula. Ranges north of the transverse ranges into the Mojave Desert in the Antelope Valley and just south of Barstow.
Also found on Santa Cruz and Santa Catalina Islands.
The species Crotalus oreganus - Western Rattlesnake, occurs from the Pacific Coast of northern Baja California north through most of California except the southern deserts, through Oregon and eastern Washington into British Columbia, Canada, and east into Nevada, Idaho, Utah, northern Arizona, extreme southwestern Wyoming, and extreme northwestern New Mexico.
Found in a wide range of habitats from seaside dunes, to desert scrub, grassy plains, rocky hillsides, chaparral, open woodlands, and agricultural areas.
Notes on Taxonomy
The taxonomy of Western Rattlesnakes is controversial and still being studied.
Some researchers still use the former species name Crotalus viridis and for them this snake remains Crotalus viridis helleri .
In a 2002 study, Douglas, Douglas, Schuett, Porras, & Holycross
[2002. Phylogeography of the Western Rattlesnake (Crotalus viridis) Complex, With Emphasis on the Colorado Plateau]. Pp. 11-50. In Biology of the Vipers [Schuett, Höggren, Douglas, and Greene (editors). Eagle Mountain Publishing, Eagle Mountain, Utah]
split C.viridis into 7 distinct species:
Some naturalists believe that rattlesnakes on Santa Catalina Island are distinct from those on the mainland and will be recognized as a different subspecies once DNA studies are completed. LA Times Article 11/28/09
Crotalus - Greek - krotalon - a rattle - refers to the rattle on the tail
oreganus - belonging to the state of Oregon - referring to the type locality, "banks of Oregon or Columbia River" helleri - honors Heller, Edmund
Timber Rattlesnake (It is not uncommon for a rattlesnake found in a forested area in California
to be called a Timber Rattlesnake. The true Timber Rattlesnake (Crotalus horridus) is not found in California. It occurs from southeast Minnesota down to central Texas and east to northern Florida up to south-central New Hampshire.)
When a Pet Gets Snake Bitten: The amazing story of Andy Cat, a very lucky cat who was bitten by a rattlesnake and survived, thanks to the smart actions of its owners.
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.
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, 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 come from the Special Animals List and the Endangered and Threatened Animals List which are published by the California Department of Fish and Wildlife.