A Guide to the Amphibians
and Reptiles of California

Southern Pacific Rattlesnake - Crotalus oreganus helleri

Meek, 1905

(= Crotalus helleri, = Crotalus viridis helleri)

Click on a picture for a larger view

Dark Blue = Range of this subspecies in California

Crotalus oreganus helleri - Southern Pacific Rattlesnake

Range of other subspecies in California:

Orange: Crotalus oreganus lutosus -
Great Basin Rattlesnake

Red: Crotalus oreganus oreganus -
Northern Pacific Rattlesnake

Gray: Intergrade Range

Click the map for a topographical view

California Rattlesnakes

Living with Rattlesnakes

Rattlesnake
Sounds and Video

Adult, San Diego County © Howard Lange

Adult, San Diego County

Adult, San Diego County
© Bruce Edley

Captive adult, courtesy of the Arizona-Sonora Desert Museum

Adult, Ventura County
© Patrick Briggs

Adult, San Diego County
© Chris Gruenwald

Adult, Santa Catalina Island
© Nathan Smith

Adult, San Diego County
© 2003 Chris Gruenwald

Adult, Los Angeles County
© Koby Poulton

Adult, near La Jolla, San Diego County, about 1/3 mile
from the beach.

Adult, Riverside County
© Michael Clarkson

Snakes of two different color variations found in the same location in San Diego County.
© Steve Bledsoe

Adult, Los Angeles County © Gregory Litiatco

Dark adult, San Bernardino County
© Jeff Ahrens

Adult found on a doorstep in Orange County. © Jay Selman

Very dark adult, Cuyamaca Mountains, San Diego County © Stuart Young

Adult, Santa Barbara County, with unusual brown coloring and a gold pattern. © Brian Hinds

Adult, Ventura County
© Wayne Darrell Crank Jr.

Adults, Santa Barbara County
© Ryan Sikola

Adult with long string of rattles, 4000 ft. San Diego County mountains
© James R. McFadden

Adult, San Diego County
© Paul Maier

High-elevation black adult with some blue coloring on some of the lower scales, San Bernardino County
© John Buckman

Adult, San Diego County © Noah Correia

This rattlesnake is in a defensive position, head back, ready to strike,
rattling its tail, and puffing itself up to look bigger and more threatening.
Click on the second photo to see an example of it expanding its size.

Adult, San Diego County © Noah Correia

Adult in defensive pose,
Orange County © Brian Nann

Adult with brownish-green coloration (resembling the coloration of a Mojave Green Rattlesnake) found in the Santa Monica Mountains, Ventura County
© Max Roberts

This adult was crossing an unpaved road one morning at the eastern edge of San Diego County. When I startled it,
it made a quick U-turn and crawled into a bush, leaving me a good look at the tracks it made in the sand.

Adult, San Diego County

Juveniles

Juvenile with yellow tail, Los Angeles County
(Note that the rattle consists of only one segment which does not produce a sound.)

Juvenile, Santa Monica Mountains,
Los Angeles County © Colin Byrne

Juvenile, about 12 inches in length, Orange County, flattening its body to appear larger. © David Fong

Juvenile with U.S. quarter-dollar coin
(2.3 cm or 15/16 ths of an inch wide)
San Diego County © Lori Paul

Juvenile, San Bernardino County
© Patrick Briggs

Dark neonate, Orange County
© Nozomi

Juvenile, San Diego County
© Verle Thompson

Pale juvenile, San Bernardino County
© Wayne Darrell Crank Jr.

Juvenile, San Diego County
© John T. Snow

Tiny juvenile in March (next to house keys for size reference),
coastal Riverside County © Brett Badeaux

Tails and Rattles

Adult tail and rattle

Adult with long rattle, San Diego County © James R. McFadden

Photos © Agata Labianca
This adult Southern Pacific Rattlesnake observed in the Santa Monica Mountains in Los Angeles County is missing the end of its tail with the rattle. It could have been bitten off by an animal or crushed by a bicycle or automobile tire or maybe some body cut it off. That's unlikely on a live snake, though it's not uncommon to find a dead rattlesnake with the rattle cut off. It's rare to find a rattlesnake without a rattle, but since it's possible, one should always learn how to recognize a rattlesnake by its other features besides the rattle - the pattern, the body shape, and the shape of the head. Pictures

There are stories circulating that rattlesnakes are evolving and losing their rattles because they no longer use them due to the fact that it's safer for them to remain silent around humans. There's no real proof that this is happening. Here's more information about that.

The tail of a newborn juvenile has only a single silent yellow button on the end of its tail. As it grows it will add rattle segments at the end of the tail behind the button, which remains at the end.

Juvenile tail and snall rattle

Unusual or Interesting Color and Pattern Variations

Melanistic patternless adult, Riverside County.
© Tony Covell

Melanistic Adult, Ventura County
© Patrick Briggs

Melanistic adult, San Gabriel Mountains, Los Angeles County
© Lori Paul. This snake had a completely dark belly.

Firefighter paramedic Chris Sperber and firefighter specialist Daniel Craig were called out to Newhall in Los Angeles County at midnight to help someone deal with a snake that was found in a bathroom next to a pool. This beautiful patternless and dark striped rattlesnake is what they found and caught. The snake was killed, following LA County Fire Departent policy, which explains why the head is missing. Photos © Ray Ortiz LACoFD.

Black adult, Santa Monica Mountains, Los Angeles County
© Colin Byrne.
Black Southern Pacific rattlesnakes are common in southern California mountains.

Pale juvenile, Orange County © Steve Bledsoe

Juvenile full from recent meal,
San Bernardino County
© Jeff Ahrens

Adult, San Bernardino Mountains, San Bernardino County © Stuart Williams.
This snake is ready to shed its skin, called being "in the blue," and it actually shows some blue coloring on the head and lower sides.

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

Southern Pacific Rattlesnakes that are almost entirely dark in color such as these occur around Southern California but they seem to be prevalent around Idyllwyld on Mount San Jacinto.

Adult hiding in pine needles, San Jacinto Mountains, Riverside County,
© Douglas Brown

Adult, near Idylwyld, San Jacinto Mountains, Riverside County
© Kim Orta & Adrian Sotomayor

Adult with green and pink coloring, San Diego County.
© Bryce Anderson

Hypomelanistic adult, San Diego County. © Bryce Anderson

Breeding Behavior

Male Combat

Two adult males wrestling for dominance on March 11th in Los Angeles County (the smaller yellower one won.) © Robert Hamilton
Watch a YouTube Video of these snakes.

Males doing a "Combat Dance,"
Ventura County © 2006 Steve Broggie

This short video shows two males wrestling for dominance over a female snake that is probably hiding nearby during the May breeding season, in Orange County. © Paul Galvin

Robert Hamilton's YouTube Video of two males wrestling for dominance.

A short video of a pair of male Southern Pacific Rattlesnakes wrestling over a mate in Los Angeles County.

Breeding Pairs

Adult male and adult female mating in March in San Diego County.
© Steve Bledsoe

A pair of breeding adults,
Orange County © Brian Nann

Pair of breeding adults exactly as found underneath a board in March in San Diego County grassland.

Feeding

Adult eating a squirrel near Idyllwild, Riverside County. This snake was fortunate to live under the deck of a building inhabited by biologists who carefully tolerated its presence and watched it emerge to take advantage of squirrels that fed beneath a bird feeder
© 2006 Sheri Lubin

Juvenile eating a Great Basin Fence Lizard in San Diego County
© Andrew Klotz

This juvenile Southern Pacific Rattlesnake was observed in Los Angeles County eating a Western Side-blotched Lizard that had been killed on a trail and was dead for some time before it was found by the snake, which took advantage of a free meal.
© Mark Rothenay

Predation

California Kingsnakes eat snakes along with other animals. They are immune to rattlesnake venom, so they
sometimes eat rattlesnakes. This one is eating a juvenile Southern Pacific Rattlesnake. © Kimberly Deutsch

This California Kingsnake is almost finished eating a juvenile Northern Pacific Rattlesnake. © Michele Coughlin

A California Striped Racer - Coluber lateralis lateralis, eating a juvenile Southern Pacific Rattlesnake in Los Angeles County. © Anthony

This Sierra Mountain Kingsnake is eating a juvenile
Northern Pacific Rattlesnake, © Patrick Briggs

A California Kingsnake eating a Southern Pacific Rattlesnake in Orange County © Ed Smith

California Kingsnake eating a Southern Pacific Rattlesnake in Los Angeles County © Chris DeGroof

This California Kingsnake was discovered eating a juvenile Southern Pacific Rattlesnake in the Los Padres Mountains, Santa Barbara County
© Benjamin Bruno

Habitat

Habitat, San Gabriel Mountains,
Los Angeles County

Habitat, San Diego County
coastal scrub

Habitat, Carlsbad, coastal
San Diego County.
(This location was bulldozed and developed a few years later.)

Habitat, San Gabriel Mountains, Los Angeles County

Habitat, coastal Riverside County

Habitat, riparian canyon,
Los Angeles County

Habitat, Santa Ana Mountains,
Riverside County

Snake in habitat, near La Jolla, San Diego County, about 1/3 mile from the beach.

Short Video and Sounds of Southern Pacific Rattlesnakes

A Southern Pacific Rattlesnake poses and rattles and crawls away at night in Los Angeles County.

A short video of two males wrestling for dominance over a female snake that is probably hiding nearby during the May breeding season, in Orange County.
© Paul Galvin

Robert Hamilton's YouTube Video of two males wrestling for dominance.

A pair of male Southern Pacific Rattlesnakes wrestle over a mate in Los Angeles County.

Listen to the rattling of a captive adult (shown above) courtesy of the Arizona-Sonora Desert Museum. © Jeff Rice / Western Soundscape Archive Not to be used without permission.

San Diego County park warning sign.

Sign at Santa Barbara
County rest area

Click on 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.

Size

Adults 30 - 44 inches long, sometimes up to 54 inches.
Neonates are about 10.5 inches in length (27 cm) (Bartlett, 2009).

Appearance

A 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.
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.

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

Ground color is brown to olive-brown.
Dark brown blotches, completely outlined by light pigment, mark the back.
These blotches turn to bars toward the tail, which is surrounded with dark rings.
The last tail ring is not well-defined and is more than twice the width of the other rings.
The underside is pale, sometimes weakly mottled.

Young

Young are born with a bright yellow tail with no rattle - just a single button which does not make a sound. They grow rattles and lose the yellow color as they age.
The pattern is brighter on juveniles than on adults.

Similar Snakes

Sympatric with other species of rattlesnakes - Crotalus ruber, Crotalus mitchellii pyrrhus, and Crotalus scutulatus on the lower northern slopes of the San Gabriel Mountains. Two other subspecies of this species also occur in California.
Notes on identifying subspecies of Western Rattlesnakes, Crotalus oreganus, found in California.

Life History and Behavior

Activity

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.

Radiotelemetry studies have shown that the home range of male snakes is larger than that of females.

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.

Apparently not all Southern Pacific Rattlesakes have the same type of venom, and this has been found in other species, also.
National Geographic 1/27/14
Sunagar, Undheim, Scheib, Gren, Cochran, Person, Koludarov, Kelln, Hayes, King, Antunes & Fry. 2014. Intraspecific venom variation in the medically significant Southern Pacific Rattlesnake (Crotalus oreganus helleri): Biodiscovery, clinical and evolutionary implications. Journal of Proteomics. 2014.

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 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.)

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.

Pits on the sides of the head sense heat. These heat sensors help the snake to locate warm-blooded prey by their temperature.

Perception

Click on this picture to see an illustrated interpretation of the various ways pit vipers (including rattlesnakes) perceive their prey, using their eyes, their sense of smell, their ability to detect vibrations, and their ability to sense heat.
© Frank Buchter

Reproduction

Rattlesnakes are ovoviparous or live-bearing. The mother keeps her fertilized eggs inside her body and gives birth to living young.
Mating typically occurs in the spring. Males search extensively for females during the mating season.
Females probably start bearing young at three years of age and breed annually. (Klauber, 1982)
An average litter consists of 4 to 12 young which are born from August to October. (Stebbins & McGinnis, 2013)
Neonates are about 10.5 inches in length (27 cm) (Bartlett, 2009).

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

Found in a wide range of habitats from seaside dunes, to desert scrub, grassy plains, rocky hillsides, chaparral, open woodlands, and agricultural areas.

Geographical Range

This subspecies, Crotalus oreganus helleri - Southern Pacific Rattlesnake, is found in California from Santa Barbara County, where there is a wide zone of intergradation with the Northern Pacific Rattlesnake north to around Morro Bay, east to the central valley and the desert slopes of the transverse and peninsular ranges, and south into the middle of the Baja California peninsula. Ranges north of the transverse ranges into the Mojave Desert in the Antelope Valley and just south of Barstow.
Also found on Santa Cruz and Santa Catalina Islands.

Known to hybridize with the Northern Mohave Rattlesnake where their ranges overlap in western Antelope Valley. (Stebbins, 2003)

The species Crotalus oreganus - Western Rattlesnake, occurs from the Pacific Coast of northern Baja California north through most of California except the southern deserts, through Oregon and eastern Washington into British Columbia, Canada, and east into Idaho, Nevada, Utah, southwestern Wyoming, western Colorado,and northern Arizona.

Elevational Range

Crotalus viridis [oreganus] has been found from sea level to around 11,000 ft. (3,350 m.) (Stebbins, 2003)

In 2010, a new elevation record for C. oreganus (lutosus) was documented at 12,112 ft. (3962 m.) Wheeler Peak, Great Basin National Park, White Pine County, Nevada. (Herpetological Review 41(1), 2010)

Notes on Taxonomy

The taxonomy of Western Rattlesnakes is controversial with several different theories. Some of these theories recommend making the three subspecies found in California full species, but this has not been widely accepted. Instead, most authorities seem to favor the split of the Western Rattlesnake species Crotalus viridis into two species - Crotalus viridis, and Crotalus oreganus.

Some authorities still use the former species name Crotalus viridis, recognizing the subspecies covered on this page as Crotalus viridis helleri.

A study published in February 2016* used head shapes and genetic analyses to determine that there are 6 full species of western rattlesnakes found in the former Crotalus viridis complex and suggested the following names, with the three species found in California shown here at the top of the list.
If this taxonomy is accepted, the ranges and common names of western rattlesnakes found in California will remain the same, but they will be full species instead of subspecies.

Crotalus helleri - Southern Pacific Rattlesnake
Crotalus lutosus - Geat Basin Rattlesnake
Crotalus oreganus - Northern Pacific Rattlesnake
Crotalus cerberus - Arizona Black Rattlesnake
Crotalus concolor - Midget Faded Rattlesnake
Crotalus viridis - Prairie Rattlesnake

* Mark A. Davis, Marlis R. Douglas, Michael L. Collyer, Michael E. Douglas. Correction: Deconstructing a Species-Complex: Geometric Morphometric and Molecular Analyses Define Species in the Western Rattlesnake (Crotalus viridis). PLOS ONE, 2016; 11 (2): e0149712 DOI:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0149712)

A 2002 study** split the Western Rattlesnake species Crotalus viridis into 7 distinct species:

Crotalus oreganus oreganus becomes Crotalus oreganus
Crotalus oreganus helleri becomes Crotalus helleri
Crotalus oreganus lutosus becomes Crotalus lutosus

Crotalys abyssus
Crotalus cerberus
Crotalus concolor
Crotalus viridis

The common names remain the same.

** 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]

Some naturalists believe that rattlesnakes on Santa Catalina Island are distinct from those on the mainland and will be recognized as a different subspecies once DNA studies are completed. LA Times Article 11/28/09

Alternate and Previous Names (Synonyms)

Timber Rattlesnake (It is not uncommon for a rattlesnake found in a forested area in California to be called a Timber Rattlesnake. The true Timber Rattlesnake (Crotalus horridus) is not found in California. It occurs from southeast Minnesota down to central Texas and east to northern Florida up to south-central New Hampshire.)

Crotalus oreganus helleri - Southern Pacific Rattlesnake (Stebbins & McGinnis 2012, SSAR 2012)
Crotalus viridis helleri - Southern Pacific Rattlesnake (Wright & Wright 1957, Stebbins 1966, 1985, Klauber 1982, 2003)
Crotalus viridis helleri (Stebbins 1954)
Crotalus viridis helleri - Southern Pacific Rattlesnake (Klauber 1949)
Crotalus viridis helleri (Meek, 1905)
Crotalus viridis (Rafinesque 1818)

Conservation Issues (Conservation Status)

None

Taxonomy
Family	Viperidae	Vipers	Crotalidae - Pitvipers
Genus	Crotalus	Rattlesnakes	Linnaeus, 1758
Species	oreganus	Western Rattlesnake	Holbrook, 1840
Subspecies	helleri	Southern Pacific Rattlesnake	Meek, 1905
Original Description
Crotalus viridis - Rafinesque, 1818 - Amer. Month. Mag. Crit. Rev., Vol. 4, No. 1, Nov. p. 41 Crotalus viridis helleri - Meek, 1905 - Field Columb. Mus. Publ. Zool., Vol. 7, p. 17 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" helleri - honors Heller, Edmund from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz
Related or Similar California Snakes
C. o. lutosus - Great Basin Rattlesnake C. o. oreganus - Northern Pacific Rattlesnake C. ruber - Red Diamond Rattlesnake C. atrox - Western Diamond-backed Rattlesnake C. s. scutulatus - Northern Mohave Rattlesnake C. c. laterorepens - Colorado Desert Sidewinder
More Information and References
California Department of Fish and Wildlife Living With Rattlesnakes California Department of Fish and Wildlife: Rattlesnakes in California University of California: Rattlesnakes Management Guide Florida Museum of Natural History: How to Safely Coexist With Snakes The Tucson Herpetological Society: Living With Venomous Reptiles Washington Department of Fish and Wildlife: Living With Snakes Centers for Disease Control and Prevention: Venomous Snakes Anapsid.org: Melissa Kaplan's Rattlesnake Information Page Southwestern Field Herping Association: Venomous Snake Safety Snake Bites California Poison Control System (search for "rattlesnake bite") UCI Health - What to do if you're bitten by a rattlesnake Snakebite Safety! How to Effectively Avoid, Identify, and Treat a Snake Bite (Includes all of the U.S.A.) Bay Nature Magazine - Are Baby Rattlesnakes the Most Dangerous Biters? The Amazing Story of Andy Cat - a very lucky pet cat who was bitten by a rattlesnake and survived, thanks to the smart actions of its owners. Wickipedia List of Fatal Snake Bites in the United States 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. 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. Eric A. Dugan, Alex Figueroa, and William K. Hayes. Home Range Size, Movements, and Mating Phenology of Sympatric Red Diamond (Crotalus ruber) and Southern Pacific (C. oreganus helleri) Rattlesnakes in Southern California. Pp. 353-364 in W. K. Hayes, K. R. Beaman, M. D. Cardwell, and S. P. Bush (eds.), The Biology of Rattlesnakes. Loma Linda University Press. 2008.

Conservation Status
The following conservation status listings for this animal are taken from the November 2020 California "Special Animals List" and the November 2020 "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.
Organization	Status Listing	Notes
NatureServe Global Ranking
NatureServe State Ranking
U.S. Endangered Species Act (ESA)	None
California Endangered Species Act (CESA)	None
California Department of Fish and Wildlife	None
Bureau of Land Management	None
USDA Forest Service	None
IUCN

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