Description. This is a medium to large snake (70-100 cm total length). It is brown or slightly greenish-brown, and has large rounded blotches along the back and black and white crossbars on the tail. Rattles are conspicuous on the tail and often give it a blunt-ended appearance.
Distribution (GAP Analysis map) The western rattlesnake occurs from southeastern British Columbia southward through Oregon and California, and into Baja California, Mexico. In Washington, it occurs only east of the Cascade Mountains and into the eastern part of the Columbia River Gorge.
Habitat. These snakes live in warm, dry habitats of desert-scrub, grassland, and open pine forest. They are most common in rocky habitats, including stream canyons.
Cool Biology Facts. Western rattlesnakes often hibernate in large numbers in rock crevices on south-facing slopes. They emerge between March and May and then disperse to their summer habitats. Females may give birth near the hibernation dens and may guard the babies for the first few days to weeks of their lives. Western rattlesnakes are calm snakes that only rarely rattle, even when approached by potential predators; instead, they prefer to remain still and avoid being seen or heard. When they do rattle, the tail vibrations are very fast, involving twitches of 20-100 times per second, depending on the temperature (warm snakes rattle faster than cool ones). A new rattle segment is added every time a snake sheds its skin; rattlesnakes often shed several times a year, depending on their age, growth rate, and health.
Conservation status. Western rattlesnakes are common in many areas, although they may only rarely be seen by people. Their hibernation dens are sensitive to habitat alteration, but western rattlesnakes do not appear to need any special statewide conservation measures at this time.