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Western Rattlesnake - Crotalus oreganus

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The size of this species varies greatly, with some populations being stunted and others growing very large. Mainland specimens often reach 100 cm in length, with the largest on record being 162.6 cm.

This species, in its various forms, shows considerable ontogenetic variation. Juveniles usually have more or less distinct patterns, but this fades as the animals mature. The color of the iris often matches the ground color, which may be bronze, gold, different shades of tan, pink or gray.

The color pattern of the typical form, C. o. oreganus, has a dark brown, dark gray, and sometimes black or pale yellowish ground color. This is overlaid dorsally with a series of large dark blotches with uneven white edges. These blotches are also wider than the spaces that separate them. Additionally, there is a lateral series of blotches that are usually darker than the dorsal blotches and clearly visible on all but the darkest specimens. The first rings of the tail are about the same color as the last body blotches, but these become progressively darker; the last two, at the base of the tail, are usually black. The belly is pale yellow, usually with brown spots. A large dark brown blotch on the snout has a pale border behind it that forms transverse bars on the supraoculars. There is a dark brown postocular stripe with a white border that extends from the eye to around the angle of the jaw.

Range & Habitat

Found in North America from southwestern Canada, though much of the western half of the United States, and south into northern Mexico. In Canada it is found in southern British Columbia. In the USA it occurs in Washington, Oregon, western and southern Idaho, California, Nevada, Utah, Arizona, and likely west-central New Mexico. In northern Mexico it is found in western Baja California (state) and the extreme north of Baja California Sur, from sea level to an altitude of 2,500 m

Behavior

Subspecies Common name Geographic range

C. o. abyssus

Grand Canyon rattlesnake

The United States, in Arizona in the Grand Canyon of the Colorado river, from the north to the south rim.

C. o. caliginis

Coronado Island rattlesnake

Mexico, on South Coronado Island, off the northwest coast of Baja California.

C. o. cerberus

Arizona black rattlesnake

The United States, in Arizona from the Hualpi Mountains and Cottonwood Cliffs in the northwest of the state, southeast to the Santa Catalina, Rincon, Pinaleno and Blue Mountains. Also found at Steeple Rock, in extreme western New Mexico.

C. o. concolor

Midget faded rattlesnake

The United States, in the Colorado and Green River basins. This area covers southwestern Wyoming, Utah east of long. 111 West (excluding the southeastern corner) and extreme east-central Colorado.

C. o. helleri

Southern Pacific rattlesnake

The United States in southern California, and Mexico in northern Baja California, west of the desert. In the north from the counties of San Luis Obispo and Kern, and south through the counties of Santa Barbara, Ventura, Los Angeles (including Santa Catalina Island), southwestern San Bernardino, Orange, western Riverside, San Diego and extreme western Imperial. From there its range extends south though Baja California to lat. 28 30' North.

C. o. lutosus

Great Basin rattlesnake

The United States in the Great Basin region. Its range includes Idaho south of lat. 44 North, Utah west of long. 111 West, Arizona west and north of the Colorado River as well as the north rim of the Grand Canyon, the entire state of Nevada (excuding Esmeralda, Nye and Clark counties), California east of the Sierra Nevada from Lower Klamath Lake south to below Lake Mono, Oregon south and east of the line Upper Klamath Lake-Fort Rock-Burns-Council (Idaho).

C. o. oreganus

Northern Pacific rattlesnake

From the Pacific slope in British Columbia, Canada, south through the United States to San Luis Obispo and Kern counties in California. This includes south-central British Columbia, Washington east of the Cascade Mountains, western Idaho from Coeur d'Alene south to near Council or Weiser, northern and western Oregon (excluding the Cascades), and California west of the Sierra Nevada. Also found on Morro Rock off the coast of San Luis Obispo county.