A Mohave Desert Sidewinder in motion on a windy night.
A Mohave Desert Sidewinder sidewinds and crawls across the desert.
Watch a Mohave sidewinder crawl at night slowly then very quickly over the sand with its unique sideways locomotion.
Listen to the faint rattling of a sidewinder
California Park warning sign.
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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.
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.
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 17 - 33 inches long. (43 - 84 cm). Snakes encountered will generally be 12 - 18 inches long.
Juveniles are about 7 inches long at birth.
A heavy-bodied venomous pit viper with a thin neck, a large triangular head, and a thick tail with a rattle on the end made of loose interlocking 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.
The supraocular scale over each eye is enlarged and raised up over the eye giving the appearance of a "horn" over each eye. These scales can fold down over the eyes to protect them when the snakes is buried or crawling in underground burrows.
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
Pale cream, tan, brown, pink, or grayish back color usually closely matches the soil surface allowing the snake to blend in with the background.
Around 40 darker blotches on the back.
A dark stripe extends through each eye.
Juveniles are born with only a single rattle button at the end of the tail.
The dark segment of the rattle closest to the body on an adult C. c. cerastes is brown,
The dark segment of the rattle closest to the body on an adult C. c. laterorepens is black.
The dark rattle segment may not become fully black on C. c. laterorepens until the snake is an adult with 3 or more rattle segments.
The last dark marks on the tail do not always correspond to the color of the dark rattle segment.
C. c. cerastes has 21 scale rows. C. c. laterorepens has 23 scale rows. C. c. laterorepens has a higher number of ventral scales than C. c. cerastes.
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.
Moves with a sidewinding locomotion, throwing raised loops of the body to the side to push itself forward in an s-sheped curve. A sidewinders trail looks like a series of parallel j-shaped lines pointing roughly 45 degrees from the direction of movement.
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.
Though the amount of venom a sidewinder injects is relatively small and rarely deadly, bites on humans are still 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 and close 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.
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. Newborn snakes have only one rattle segment which does not make a sound.
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 mainly lizards when young, and increasingly larger prey including small rodents when grown.
An ambush hunter, it sits buried beneath the surface of loose sand with just the top of the head showing, near kangaroo rat warrens, and lizard or rodent trails, then strikes at and releases the prey. The snake then follows the trail of the envenomated animal and swallows it whole.
Young snakes may use their tail to lure their prey (caudal luring.) They coil up and lie still, raise up the tail, and wiggle it.
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.
Rattlesnakes are ovoviparous. 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. (Klauber, 1982)
Mating occurs in the spring.
Two to 18 young are born from July to September. (Stebbins & McGinnis, 2013)
Inhabits primarily areas of wind-blown sands, especially where sand hummocks are topped with vegetation. Also found in hardpan, open flats, rocky hillsides, and other desert areas, especially those grown with creosote bush, where the terrain is open, not obstructed by rocks or vegetation, allowing the broad sidewinding locomotion.
This subspecies, Crotalus cerastes cerastes - Mohave Desert Sidewinder, is found in south-central California south and east of the Sierras south to roughly the San Bernardino county line.
The species Crotalus cerastes - Sidewinder, is found in the Southern California deserts, east through southern Nevada to extreme southwestern Utah, into western Arizona, and south into northeast Baja California Mexico, and northwest Sonora, Mexico.
Notes on Taxonomy
According to SSAR Herpetological Circular No. 43, 9/17 -
"Douglas et al. (2006, Mol. Ecol. 15: 3353–3374), using mtDNA, found several geographically distinct lineages within C. cerastes. Only one of these lineages corresponded to a recognized subspecies. (C. c. laterorepens).
'The spelling of the word "Mojave" or "Mohave" has been a subject of debate. Lowe, in the preface to his "Venomous Reptiles of Arizona" (1986) argued for "Mohave" as did Campbell and Lamar (2004, "The Venomous Reptiles of the Western Hemisphere"). According to linguistics experts on Native American languages, either spelling is correct, but using either the "j" or "h" is based on whether the word is used in a Spanish or English context. Given that this is an English names list, we use the "h" spelling (P. Munro, Linguistics, UCLA, pers. comm.).'
(Taxon Notes to Crotalus scutulatus, SSAR Herpetological Circular no 39, published August 2012, John J. Moriarty, Editor.)
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.
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.