● Venomous · Native to western North America
Western rattlesnake
Crotalus oreganus Holbrook, 1840
Data updated October 2026
At a glance
A heavy-bodied pit viper of hillsides, grasslands, sagebrush and open woods from Southern California to British Columbia. Color varies with its surroundings. It is defensive rather than aggressive and often lies still and relies on camouflage before it rattles.
01
Identification
The western rattlesnake is a heavy-bodied pit viper with a thin neck, a broad triangular head and a rattle at the tip of the tail. Its ground color changes with its surroundings and can be olive-green, gray, brown, golden or tan. A row of dark blotches runs down the back, often edged in black and then white, and the belly is pale. Its scales are strongly keeled, which gives it a dull look. Young are more brightly patterned than adults and are born with a single silent button instead of a working rattle. The species includes several forms, among them the Northern Pacific, Southern Pacific and Great Basin rattlesnakes.
- 01Eye stripe. A light stripe runs from behind the eye down to the corner of the mouth.
- 02Blotched back. Dark brown spots along the spine, usually bordered with black and then a pale edge.
- 03Pit viper features. A heat-sensing pit on each side of the face near the nostril and vertical, cat-like pupils. In Washington it is the only snake with a rattle and facial pits.
Commonly confused with
02
Size
Most adults measure about 15 to 36 inches (38–91 cm), and those in Oregon and Washington average around 2 feet. Some reach 48 inches (121 cm). The longest on record measured about 59 to 60 inches, roughly 5 feet. Newborns are about 10.5 inches (27 cm) long.
03
Range & habitat
Western rattlesnakes are found through most of California outside the southern deserts and north through Oregon, eastern Washington, extreme northwestern Idaho and the dry interior valleys of southern British Columbia, with the Great Basin form living farther east. In Washington they live east of the Cascades. They have been recorded from sea level to about 11,000 ft. Typical habitat includes rocky hillsides, talus slopes and outcrops, rocky stream courses, grassland, chaparral, sagebrush and shrub-steppe, oak and ponderosa pine woodland, pinyon-juniper and montane forest. They often live near people.
04
Diet & predators
Western rattlesnakes hunt mainly by ambush, waiting near cover and using their heat-sensing pits to find warm-blooded prey, though they also search actively. After a strike they follow the scent trail of the bitten animal and swallow it whole. Small mammals make up most of the diet, especially mice and voles, along with ground squirrels, chipmunks, pocket gophers and prey as large as rabbits. Birds, lizards, frogs, other snakes and insects are also eaten.
Feeds on
- Mice and voles
- Ground squirrels, chipmunks and rabbits
- Birds
- Lizards, frogs and small snakes
Preyed on by
- Other snakes
- Hawks and other raptors
- Black bears
- Skunks
05
Behavior & seasons
Western rattlesnakes are defensive rather than aggressive. When disturbed they may rattle, or stay silent and rely on camouflage, and they rarely strike unless they are harassed, handled or stepped on. They are active by day in mild weather and switch to dusk and night activity during summer heat. Males wrestle in “combat dances” that do not injure either snake.
In colder parts of the range they spend winter in communal dens in rock cracks, talus slopes, caves or burrows that stay above freezing, sometimes with other snake species. They leave the dens in March or April; in Washington they linger nearby for two or three weeks before moving out to summer feeding areas. In British Columbia most stay within about 1 mile (1.5 km) of the den, while Oregon snakes may travel up to 2 miles. They return to the dens from late September to mid-October and can spend about 180 days a year underground. The same dens may be used for generations.
06
Reproduction
Western rattlesnakes give birth to live young. Mating takes place in spring near the den or in late summer, when females can store sperm and delay fertilization until the following spring. Litters of about 3 to 12 young are born from late August to October, and newborns may stay in their mother’s den through their first winter. How often females breed varies with climate: some California populations probably breed every year, while in Oregon and British Columbia females reproduce only every two to four years.
07
Conservation
The western rattlesnake is not listed under the federal Endangered Species Act and remains common in much of its range. It has declined in many areas, though. It is a Sensitive Species in Oregon, where development has left only three small known sites in the Willamette Valley, and it is blue-listed (of special concern) in British Columbia. In Washington it may be collected only with a scientific permit. The main threats are habitat loss, road deaths, and killing of snakes at their dens, which can wipe out a local population.
08 — Bite safety
If someone is bitten
Western rattlesnake bites are medically serious, and every bite needs medical care. Call 911 or go to the nearest emergency department. For guidance, call Poison Control at 1-800-222-1222. If a pet is bitten, take it to a veterinarian right away.
This page does not give first-aid or treatment instructions. Read our safety disclaimer.
Keep reading
Sources
- California Herps — Northern Pacific rattlesnake (Crotalus oreganus oreganus)
- Washington Department of Fish and Wildlife — Western rattlesnake
- Oregon Conservation Strategy (ODFW) — Western rattlesnake fact sheet
- B.C. Ministry of Environment — Western rattlesnake species account
Data updated October 2026 · How we build these pages