Several views of a Northern Mohave Rattlesnake rattling and taking a defensive posture.
A Northern Mohave rattlesnake crawls off a road in Arizona.
Click on the play button or the speaker to hear a Mojave Rattlesnake rattling
California Park 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 24 - 51 inches long (61 - 129 cm) Most snakes encountered are from 18 - 40 inches in length. Newborns are about 10.5 inches.
A heavy-bodied, dangeously venomous pit viper, with a thin neck and a large triangular head.
Pupils are elliptical.
Scales are keeled.
Usually there are 2 or 3 large scales on the top of the head between the supraoculars.
Rattlesnakes are "pit vipers" which means they have two pits that are used to sense heat when hunting warm-blooded prey - with one pit on each side of the front of the head above the mouth.
Color and Pattern
A light stripe runs from behind the eye diagonally to the upper lip beyond the end of the jaw, but does not cross over the lip.
(The posterior light stripe of the Western Diamond-backed Rattlesnake extends to the upper lip in front of the end of the jaw, crossing over the lip.)
Ground color varies from greenish gray, yellow, tan, olive green, to brown. Irregular, dark, well-defined, diamond or near diamond-shaped dorsal markings.
Black and white rings surround a thick tail. The black rings are narrower than the light rings, and often offset. A rattle on the end of the tail, consisting of loose interlocking segments. A new rattle segment is added each time the skin is shed.
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
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. Not active during cooler periods in Winter.
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.
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 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. 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, mice, rats, rabbits and hares, and occasionally lizards, snakes, and toads.
(Adult California Ground Squirrels are immune to rattlesnake venom and will intensely confront any snake they feel to be a threat.)
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 immobilize 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.
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)
Two to 17 young are born between July and 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)
You can see two male Northern Mohave Rattlesnakes wrestling in this UTube movie.
Inhabits grassland, desert scrub, rocky slopes, creosote bush flats, open juniper woodland, and light chaparral.
Found in southeastern California from the Colorado river north of the San Bernardino County line, west through the Mojave desert to the Antelope Valley, to Walker Pass in the Sierra Nevada, and east of the Sierra Nevada into Inyo County. Absent from the southeastern Colorado deserts, but there are unconfirmed reports of sightings west of the Colorado River in Imperial County.
Outside of California, the species ranges north into Nevada and Utah, east into west Texas, and far south into Mexico.
(Subspecies are sometimes recognized, but I don't know their exact ranges outside of California.)
Notes on Taxonomy
'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.
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.
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.
This snake is not included on the Special Animals List, which indicates that there are no significant conservation concerns for it in California.