Top of head showing several small scales between intraoculars. Compare with the two large scales between the supraoculars of the Northern Mohave Rattlesnake.
California National Wildlife Refuge warning sign, Imperial County.
Click the picture to see more rattlesnake signs.
Short Videos and Sound
Several views of a Cochise County, Arizona Western Diamond-backed Rattlesnake rattling and taking a defensive pose with its head and tail elevated. It keeps rattling as it crawls away into a bush.
A Western Diamond-backed Rattlesnake rattles in a defensive pose in Sierra County, New Mexico.
Listen to an Arizona
Western Diamond-backed Rattlesnake rattle and hiss.
(This is the snake)
California 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 typically described as poisonous, but they are actually venomous.
A poisonous snake is one that is harmful to eat. A venomous snake injects dangerous venom into its victim.
A bite from a rattlesnake can be extremely dangerous, but rattlesnakes should not be characterized as aggressive and vicious, striking and biting without provocation, as they are often shown. If rattlesnakes are given some space and enough time to escape to a safe place, they will usually just crawl away as fast as possible to 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 up this way to strike and bite. 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.
Rattlesnakes do not always rattle a warning. Sometimes they rattle loudly to warn potential enemies of their presence, but other times they remain silent when they sense a threat, choosing to remain still to rely on their cryptic color and pattern to let them blend into their surroundings to hide from the threat. Making a noise in this situation risks advertising their presence. They also use their natural camouflage to hunt by sitting still, without rattling, trying to remain invisible as they wait for a warm-blooded prey animal to pass close enough to strike.
Description
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.
Length
Adults grow to 30-90 inches (76-229 cm). (Stebbins, 2003)
Most snakes encountered are from 1 to 4 feet in length.
The largest rattlesnake in California, and in the West.
(Only the Eastern Diamond-backed Rattlesnake is larger, growing to 96 inches (243.8 cm) (Stebbins & McGinnis, 2012)
Appearance
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.
Usually 4 or more small scales occur on top of the head between the supraocular scales.
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
The ground color and the intensity of the pattern are variable, often matching the habitat; grey, brown, olive, tan, or yellowish.
Diamond-shaped blotches on the back are brown or black, with light edges.
Markings are sometimes indefinite giving a dusty overall appearance.
Broad black and white rings, fairly equal in width, circle a thick tail just before the rattle.
(Commonly called a "coontail" since it resembles the tail of a racoon.)
The ring adjacent to the rattle is usually black.
A light stripe extends from behind the eye diagonally to the upper lip in front of the end of the jaw crossing over the lip.
The light stripe behind the eye on the similar Northern Mohave Rattlesnake extends back beyond the end of the jaw and does not cross the lip.)
Young
The markings on young snakes are more discinct than markings on adults.
Newborn snakes do not have a rattle - just a single button which does not make a sound.
Compare the Western Diamond-backed Rattlesnake to the Northern Mohave Rattlesnake
Also similar to and easily confused with the Red Diamond Rattlesnake - Crotalus ruber, but in California the ranges of these two snakes barely meet, and the Red Diamond Rattlesnake is typically light reddish brown or red in color.
See this page:
Comparethe Western Diamond-backed Rattlesnake to the Red Diamond Rattlesnake
Life History and Behavior
Activity
Primarily nocturnal during periods of excessive daytime heat, but active during daylight when the temperature is more moderate. Not active during cooler periods in Winter.
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.
A bite from any kind of rattlesnake of any age or any size should be treated as a serious medical emergency, but the bite of a juvenile rattlesnake is not more dangerous than the bite of an adult.
Experts disagree whether or not juvenile rattlesnake venom is more potent than adult rattlesnake venom, but this does not really make much difference in the severity of a bite.
While adult rattlesnakes can control the amount of venom they inject depending on their needs (small animals need less venom, a defensive or warning bite may need no venom, etc.), it is often assumed that juvenile rattlesnakes do not have the same ability and that they always inject the full amount of venom they have available. Some studies show this is not true.
There is also no proof that adult rattlesnakes are more likely than juveniles to bite without injecting venom when they are biting as a warning. Regardless of these things, adults have far more venom to inject than juveniles so the potential danger from the bite of an adult is significantly higher than the danger from the bite of a juvenile. Even when an adult does not inject the full amount of venom it has available, it most likely injects more venom than a juvenile would inject.
Venomous snakes are immune to the venom of their own species, so if a snake is bitten during interactions with other snakes of its species during territorial fights or during mating or if it accidentally bites itself, it will not suffer from the venom. However, they are not typically immune to the venom of other species of snakes.
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.
Defense
When disturbed, in self-defense Western Diamond-backs will often aggressively hold their ground, raising the head high in a striking coil with the tail elevated and rattling, and hissing loudly.
Even a dead snake can bite and inject venom if the jaws reflexively open and close when they are touched.
Diet and Feeding
Eats small mammals, birds, and lizards. Juveniles sometimes eat large insects and frogs.
Pits on the sides of the head sense heat. These heat sensors help the snake to locate warm-blooded prey by their temperature.
An ambush hunter, it typically sits near the trail of a mammal, waiting for it to pass by, then strikes at and releases the prey. The snake then follows the trail of the envenomated animal and swallows it whole.
Rattlesnakes are ovoviviparous. The mother keeps her fertilized eggs inside her body and gives birth to living young.
Females probably start bearing young at three years of age and breed annually.
Mating occurs in the spring.
Young are born
between late August and early October. (Klauber, 1982)
Four to 25 young are born in a litter. (Stebbins & McGinnis, 2013)
Male "Combat Dance"
Adult males engage in a ritual "Combat Dance" during the spring breeding season and at other times. Throughout much of history this activity was presumed to be a mating male and female instead of two competing males. Despite the common name, it is not combat as neither male is injured. And it's not a dance, it's essentially a wrestling match in which necks and forebodies are intertwined, with the stronger snake slamming the smaller one to the ground until the weaker snake leaves the area. Most bouts end in a draw.
"Certainly the presence of a female is not necessary to stimulate males to dance."
"Dancing is not restricted to a single season of the year."
(Klauber, 1982)
Habitat
In California inhabits only desert areas in the southern Mohave Desert and throughout most of the Sonoran Desert in California. May also be found in areas in the desert modified by urban development or agriculture.
The species throughout its range inhabits arid and semiarid areas including plains and mountains, woodlands and pine forests, deserts, canyons and rocky vegetated foothills.
Geographical Range
Found in southeast California in Imperial, Riverside, and San Bernardino Counties.
(The 1990 California Dept. of Fish and Game California Wildlife Habitat Relationships System range map for the species shows it ranging farther west into San Diego County, overlapping the range of C. ruber.)
Outside of California, the species ranges through much of Arizona, New Mexico, Oklahoma, and Texas, into Arkansas, and south into Mexico.
Elevational Range
Generally found at elevations less than 1000 ft. (300 m).
Crotalus - Greek - krotalon - a rattle - refers to the rattle on the tail
atrox - Latin - atrox dark, fierce, savage - referring to the sometimes savage disposition of this species
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.
Flaxington, William C. Amphibians and Reptiles of California: Field Observations, Distribution, and Natural History. Fieldnotes Press, Anaheim, California, 2021.
Samuel M. McGinnis and Robert C. Stebbins. Peterson Field Guide to Western Reptiles & Amphibians. 4th Edition. Houghton Mifflin Harcourt Publishing Company, 2018.
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.
Joseph Grinnell and Charles Lewis Camp. A Distributional List of the Amphibians and Reptiles of California. University of California Publications in Zoology Vol. 17, No. 10, pp. 127-208. July 11, 1917.
Conservation Status
The following conservation status listings for this animal are taken from the October 2021 California "Special Animals List" and the October 2021 "State and Federally Listed Endangered and Threatened Animals of California" list, both of which are produced by multiple agencies and available here: https://www.wildlife.ca.gov/Data/CNDDB/Plants-and-Animals. You can check the link to see if there are more recent lists.
If no status is listed here, the animal is not included on either 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.
This snake is not included on the Special Animals List, which indicates that there are no significant conservation concerns for it in California.
