DistributionRead full entry
Global Range: (20,000-200,000 square km (about 8000-80,000 square miles)) Range includes Pacific drainages from the upper reaches of the Willamette River system, Oregon (west of the Cascades crest), south to the upper San Gabriel River, Los Angeles County, California, including the coast ranges and Sierra Nevada foothills in the United States (Stebbins 2003). The species occurred at least formerly in a disjunct location in northern Baja California: two specimens (identified by R. C. Stebbins and R. G. Zwiefel) were collected in 1965 at an elevation of 2,040 meters at the lower end of La Grulla Meadow, Sierra San Pedro Martir, Baja California, Mexico (Loomis 1965); subsequent searches have not detected the species in that area (Grismer 2002, Stebbins 2003). The species apparently has disappeared from portions of its historical range, especially in southern California (see Hayes and Jennings 1988). Extant R. boylii populations are not evenly distributed in California; in the Pacific Northwest, 40 percent of the streams support populations, whereas that number drops to 30 percent in the Cascade Mountains (north of the Sierra Nevada), 30 percent in the south coast range (south of San Francisco), and 12 percent in the Sierra Nevada foothills (Fellers 2005). Elevational range extends from sea level to around 2,130 meters.