California Reptiles & Amphibians

Crotalus oreganus oreganus - Northern Pacific Rattlesnake

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Range in California: Red

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to the other subspecies.

Venomous and Potentially Dangerous!

Adult, Contra Costa County

Adult, Fresno County

Adult, Yuba County

Adult, Contra Costa County

Adult, Alameda County

Adult, Napa County

Adult, Santa Cruz County

Juvenile, Kings County

Adult, Del Norte County © Alan Barron

Adult, Fresno County
© Patrick Briggs

Adult, Sutter Buttes, Sutter County.
© Jackson Shedd.
Specimen courtesy of Eric Olson.

Greenish adult, Lake County.
© Lawrence Anderson

Adult, Shasta County © Richard Gentile

Intergrade with C. o. helleri , Santa Barbara County © Benjamin German

Some older rattlesnakes often have very long rattle strings, especially those in captivity such as this one in a Bend Oregon museum.

Adult eating a rodent, Kern County. © Renee Simpson

Sub-adult, San Benito County

Adult, Greenhorn Mountains, Kern County

Adult, San Mateo County, ready to shed - showing very little contrast in its pattern. © Melissa Amarello

Panamint Rattlesnake - Crotalus mitchellii stephensi, Inyo County © Carl Brune

C. o. oreganus near its southern range limit is variable in appearance, sometimes with markings similar to C. o. lutosus. Identification of rattlesnakes found in this region can be confusing and open to debate. I have received several comments that I might have mis-identified snakes from this region - that they could be intergrades or hybrids, or that the Kern County snake depicted above is actually C. o. lutosus. However, it is a C. o. oreganus, based on appearance, location, and some preliminary genetics work that has been done in the area. The Inyo county rattlesnake depicted above from the southern Sierras has been identified on sight by various viewers of this photo as C. o. oreganus as well as a young Panamint Rattlesnake - Crotalus mitchellii stephensi.

Rumors of C. oreganus x C. mitchelli stephensi hybrids have not yet been confirmed by genetic analysis. Some of these controversies should be resolved when the results of further studies on these species are published.

According to the herpetologist Robert Hansen, who has studied in depth the reptiles and amphibians of the Southern Sierra Nevada Mountains and the surrounding regions: "Among populations of "oreganus" inhabiting arid landscapes near their southern range limits (e.g., southern San Joaquin Valley, Carrizo Plain), there is a tendency toward small size, light ground color, and reduced dorsal blotch size...features that cause these snakes to superficially resemble lutosus."..."The southern extent of the range of lutosus in eastern California (e.g., the Mono/Inyo counties region) has been mapped in reasonable detail, and thus far, there are no known instances where the ranges of oreganus and lutosus come into contact.
However, farther north, where the Sierra Nevada crest is much lower and the potential for populations of oreganus and lutosus to meet is likely greater, careful field studies are lacking. Ultimately, reliance on features of coloration and pattern to distinguish one form from the other in areas of potential contact is not advised."

Habitat, Alameda County

Habitat, Contra Costa County

Habitat, Yuba County

Habitat, Fresno County

Habitat, Kings County

Habitat, Contra Costa County

Habitat, Contra Costa County
© Erik Grouell

Den site, Contra Costa County
© Erik Grouell

Adult, basking at ege of a den (a deep crack in a large boulder) in early March, Kern County

Tail

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rattlesnake signs.

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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.

Description

Venomous

The venom of this snake is potentially dangerous to humans.

Size

Adults 15 - 36 inches long, ( 38 - 91 cm) sometimes up to 48 inches (121 cm) with 60 inches being the longest (151 cm).

Appearance

A heavy-bodied, venomous pit viper, with a thin neck and a large triangular head. Pupils are elliptical. Scales are keeled. Usually with a light stripe extending diagonally from behind the eye to the corner of the mouth.

The ground color is variable, matching the environment - olive-green, gray, brown, golden, reddish brown, yellowish, or tan. Dorsal blotches on the front 2/3 of the body, change to dark bars on the body and dark and light rings on the tail which are well-defined and of fairly uniform width. Young have a bright yellow tail. The underside is pale, sometimes weakly mottled.

Dark brown or black blotched markings, usually with dark edges and light borders, mark the back, with corresponding blotches on the sides. This pattern is brighter on juveniles than on adults.

A rattle, consisting of loose interlocking segments, usually occurs at the end of the tail. A new rattle segment is added each time the skin is shed. Newly-hatched snakes do not have a rattle - just a single button which does not make a sound.

Heat sensing pits on the sides of the head 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 prey. The snake can control the amount of venom injected and the fangs are replaced if broken. Bites on humans are potentially dangerous without immediate medical treatment. Even a dead snake can bite and inject venom if the jaws reflexively open when they are touched.

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. In colder areas, known to den in burrows, caves, and rock crevices, sometimes in large numbers, and sometimes with other snake species.

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.

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

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.)

Reproduction

Live-bearing; young are born August - October.

Range

Found in California from Santa Barbara county, where it intergrades with the Southern Pacific Rattlesnake, east to the Sierras, and north from the coast to the Sierras and west of the Cascades ranges. Ranges north through Oregon, west of the Cascades in Washington and into British Columbia, Canada, and east west-central Idaho.

Habitat

Inhabits rocky hillsides, talus slopes and outcrops, rocky stream courses, rocky areas in grasslands, mixed woodlands, montane forests, pinyon juniper, sagebrush. Sea level to around 11,000 ft.

Taxonomic Notes

The taxonomy of Western Rattlesnakes is controversial and still being studied.
Some researchers still use the name which this snake held for many years: Crotalus viridis oreganus. Others have split C.viridis into 7 distinct species, including Crotalus oreganus.

Conservation Issues (Conservation Status)

None.

Taxonomy
Family	Viperidae	Vipers
Genus	Crotalus	Rattlesnakes
Species	oreganus	Western Rattlesnake
Subspecies	oreganus	Northern Pacific Rattlesnake
Original Description
Crotalus viridis - Rafinesque, 1818 - Amer. Month. Mag. Crit. Rev., Vol. 4, No. 1, Nov. p. 41 Crotalus viridis oreganus - Holbrook, 1840 - N. Amer. Herp., Ed. 1, Vol. 4, p. 115, pl. 29 [24 in text] from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz
Meaning of the Scientific Name
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" from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz
Alternate Names
Known for many years as Crotalus viridis oreganus Crotalus oreganus.
Related or Similar California Snakes
C. o. helleri - Southern Pacific Rattlesnake C. o. lutosus - Great Basin Rattlesnake C. atrox - Western Diamond-backed Rattlesnake C. s. scutulatus - Northern Mohave Rattlesnake C. m. stephensi - Panamint Rattlesnake
More Information and References
Natureserve Explorer California Dept. of Fish and Game Living With Rattlesnakes Tucson Herpetological Society: Living With Venomous Reptiles pdf California Department of Fish and Game: Rattlesnakes in California Rattlesnake Bites California Poison Control System: Rattlesnake Bites University of Arizona: Rattlesnakes Justin Schwartz' Rattlesnake Bite Story and Pictures Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003. Behler, John L., & F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992. Bartlett, R.D. , & Alan Tennant. Snakes of North America - Western Region. Gulf Publishing Co., 2000. 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. Brown, Philip R. A Field Guide to Snakes of California. Gulf Publishing Co., 1997. Ernst, Carl. H. Venomous Reptiles of North America. Smithsonian Institution Press, 1999. 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.

Conservation Status
The following status listings come from the Special Animals List which is published several times each year by the California Department of Fish and Game. This snake is not included on the Special Animals List, which indicates that there are no significant conservation concerns for it in California.
Organization	Status Listing
U.S. Endangered Species Act (ESA)
California Endangered Species Act (CESA)
California Department of Fish and Game
Bureau of Land Management
USDA Forest Service
Natureserve Global Conservation Status Ranks
World Conservation Union - IUCN Red List