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:''Common names: western rattlesnake,〔Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.〕 northern Pacific rattlesnake, Pacific rattlesnake,〔Wright AH, Wright AA. 1957. Handbook of Snakes. Comstock Publishing Associates. (7th printing, 1985). 1105 pp. ISBN 0-8014-0463-0.〕 more'' ''Crotalus oreganus'' is a venomous pit viper species found in North America in the western United States, parts of British Columbia, and northwestern Mexico. Seven subspecies are currently recognized, including the nominate subspecies described here.〔 ==Description== The size of this species varies greatly, with some populations being stunted and others growing very large. Mainland specimens often reach in length, with the largest on record being (Klauber, 1956)〔 for ''C. o. oreganus''.〔Klauber LM. 1997. Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind. Second Edition. First published in 1956, 1972. University of California Press, Berkeley. ISBN 0-520-21056-5.〕 This species, in its various forms, shows considerable ontogenetic variation. Juveniles usually have more or less distinct patterns, but these fade as the animals mature. The color of the iris often matches the ground color, which may be bronze, gold, or different shades of tan, pink, or gray.〔 The color pattern of the typical form, ''C. o. oreganus'', has a dark-brown, dark-gray, olive-brown, or sometimes black or pale yellowish ground color 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, a lateral series of blotches, usually darker than the dorsal blotches, is 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 rings become progressively darker; the last two rings, 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.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Crotalus oreganus」の詳細全文を読む スポンサード リンク
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