Varies by area and subspecies: up to 63 in. excluding rattle (Arizona); largest in the Northwest 59 in., most Washington adults around 2 ft; 18 to 36 in. average (Oregon); C. o. concolor rarely over 26 in. (Colorado).
How to recognize it
Rattle on the tail; broad triangular head; facial pits
Vertical pupils and heat-sensing pits near the nostrils
Venom: “Caution: This is a venomous and potentially dangerous snake.” (Washington Department of Fish and Wildlife)
Range: Western rattlesnakes occur east of the Cascade Mountains in the East Cascades, Columbia Basin, Okanogan, and Blue Mountain ecoregions. The furthest west they have been documented is in the Columbia Gorge approximately 1 mile west of Dog Mountain in Skamania County.
Habitat: In Washington, western rattlesnakes primarily occur in shrubsteppe habitats but are also found in Oregon white oak, ponderosa pine and other open forest types. (Washington Natural Heritage Program, Washington Department of Fish and Wildlife, BLM and U.S. Forest Service)
“This snake is common and widespread in eastern Washington.”
“Caution: This is a venomous and potentially dangerous snake.”
“In most of the Columbia Basin, western rattlesnakes emerge from their overwintering sites (hibernacula or dens) in April.”
“Adults return to the overwintering sites starting in late September, although activity may continue until late October depending on location and temperatures.”
“Rattlesnakes are active during the day when temperatures are moderate but switch to nocturnal activity during the hottest months of the year.”
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