Crotalus oreganus oreganus - Northern Pacific Rattlesnake
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 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
This subspecies, Crotalus oreganus oreganus - Northern Pacific Rattlesnake, is 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. Out of California it continues north through Oregon, west of the Cascades in Washington and into British Columbia, Canada, and east west-central Idaho.
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 Nevada, Idaho, Utah, northern Arizona, extreme southwestern Wyoming, and extreme northwestern New Mexico.
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.
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