California Reptiles & Amphibians

Crotalus oreganus oreganus - Northern Pacific Rattlesnake

(=Crotalus oreganus)

Click on a picture for a larger view

Range in California: Red

Click the map for a guide
to the other subspecies.

Rattlesnake Sounds and Video

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, Santa Clara County
© Leo Gomez

Reddish adult, Kern Plateau, Kern County © Sam Wilson

Sub-adult, Santa Cruz County.
© Norbert Fanjat

Adult, Santa Clara County © John Worden

Sub-adult, San Benito County

Very dark adult from western Kern County © Mike Waters

Oddly-patterned juvenile from western Kern County © Mike Waters

Adult eating a rodent, Kern County. © Renee Simpson

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

Tail

Click on the play button or the speaker to hear a rattlesnake rattling

Click on the picture to see more
rattlesnake signs.

Adult, Greenhorn Mountains, Kern County

Robert Herndon found this adult snake near Three Rivers in Tulare County.
© Robert Herndon

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 left 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 right from the southern Sierras has been identified by various viewers of the photo as C. o. oreganus or C. o. lutosus, or as a young Panamint Rattlesnake - Crotalus mitchellii stephensi which is what it is.

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 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

Habitat, Alameda County

Habitat, Contra Costa County

Habitat, Yuba County

Habitat, Fresno County

Habitat, Kings County

Habitat, Contra Costa County

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

Short Videos

A Northern Pacific Rattlesnake in Contra Costa County coils defensively and rattles sensing the air with its tongue.

A juvenile rattlesnake rattles and crawls off a road in the foothills of Fresno County in early Fall.

Rattle

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. Newborn 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 species Crotalus viridis and this snake remains Crotalus viridis oreganus.

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:

Crotalus oreganus oreganus becomes Crotalus oreganus,
Crotalus oreganus helleri becomes Crotalus helleri, and
Crotalus oreganus lutosus becomes Crotalus lutosus.

The common names remain the same.

This taxonomy was accepted by a snake systematist group in 2009 and is already in use by the CNAH. The SSAR will most likely use this taxonomy in its next list.

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
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 University of California: Rattlesnakes Management Guide Rattlesnake Bites California Poison Control System: Rattlesnake Bites University of Arizona: Rattlesnakes Justin Schwartz' Rattlesnake Bite Story and Pictures Sean Bush MD: Venom ER - When snakes strike! 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. & 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. 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. 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 of the United States. Tricolor Books, 2009. 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.

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

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