Global Range: (20,000-200,000 square km (about 8000-80,000 square miles)) Discontinuous distribution in west-central California: coast ranges between Sonoma and Santa Barbara counties, Central Valley and surrounding foothills from southern Colusa County to northwestern Kern County on the west side of the valley and southern Butte County to northern Tulare County on the east side.
This species has been eliminated from much of the historical range in the Central Valley as a result of agricultural and urban development (Stebbins 1985), but it still occurs throughout most of overall historical range and can be locally common (Trenham et al. 2000). About 80% of all extant occurrences are in Alameda, Contra Costa, Madera, Merced, Monterey, San Benito, ad Santa Clara counties, with 30% of all occurrences in Alameda County. Recently rediscovered on the San Francisco Peninsula (Lagunita Lake, Stanford University) (Barry and Shaffer 1994). See Jennings (1996, Herpetological Review 27:147) for an old record from San Mateo County. Elevational range from near sea level to 1054 m.
The Sonoma County population is geographically separated from the closest populations (in Contra Costa, Yolo, and Solano counties) by the Coast Range, Napa River, and the Carquinez Straits, a distance of about 72 km. This population occurs on the Santa Rosa Plain, an area of about 6.8 x 4.4 km (USFWS 2002). The historical range may have included the Petaluma River watershed, as there is one record of a specimen from the vicinity of Petaluma from the mid-1900s (Borland 1856, cited by Storer 1925).