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Global Range: (20,000-200,000 square km (about 8000-80,000 square miles)) Historical range included high-elevation areas of the Sierra Nevada and Cascade mountain ranges in California, from Tulare County north to Sierra County, and from the vicinity of Lassen Peak and Mt. Shasta west to the Trinity Mountains in Trinity County, with a recent study indicating that the historical range also included the southern Cascade mountain range in Oregon, as far north as the Columbia River (see USFWS 2012).
Elevational range extended from as low as 1,180 meters in Yosemite Valley to as high as 3,630 meters in the southern Sierra Nevada (Grinnell et al. 1937, Gould 1978, Biosystems Analysis 1989, Schempf and White 1977). This fox seldom has been detected below 1,500 meters and is most often observed above 2,100 meters (Perrine et al. 2010).
The current distribution is believed to be restricted to a few small populations: one in the vicinity of Lassen Peak, another in the vicinity of Sonora Pass (Statham et al. 2012, USFWS 2012); and ocasional evidence indicating the existence of small number populations in the Cascades of Oregon (D. Clayton, J. von Kienast, K. Aubry, pers. comm., cited by Statham et al. 2012; recent photo evidence from Mt. Hood National Forest ad Crater Lake National Park). The U.S. Forest Service recently conducted carnivore surveys on National Forest System lands throughout the Sierra Nevada, but Sierra Nevada red fox were detected only in the Lassen National Forest and Humboldt-Toiyabe National Forest (see USFWS 2012).
Hall (1981) mapped the range as extending from northern and central California east through most of central Nevada. However, Hall (1946) indicated that the subspecific identity of red foxes in Nevada was uncertain; he suggested that foxes in the Sierra Nevada might be subspecifically different from at least some of those occurring farther east in Nevada. Subsequently the subspecies necator was presumed to range from the northern California Cascades east to the northern Sierra Nevada, then south through the mountains to Tulare County, though the distribution was regarded as poorly known (Biosystems Analysis 1989). As of the late 1980s, the subspecies was thought to be most numerous (though still uncommon) in the vicinity of Lassen Volcanic and Yosemite national parks, but this conclusion may have reflected the distribution and abundance of human observers rather than of foxes (California Department of Fish and Game 1987). Perrine et al. (2010) described the historical range as "throughout high elevations of the Sierra Nevada from Tulare County northward to Sierra County, and from Mount Shasta and Lassen Peak westward to the Trinity Mountains (Trinity County."
More recently, genetic studies indicated that red foxes in the Sierra Nevada should be regarded as consubspecific with those in the southern Cascades (through Oregon northward to the Columbia River) (Sacks et al. 2010). Additionally, red foxes in eastern half of Nevada appeared to be more closely related to those in the Rocky Mountains than to those in the Sierra Nevada. So the range of subspecies necator apparently encompasses the Sierra Nevada and Cacade Mountains (California, Oregon, extreme western Nevada) but not areas to the east in central and eastern Nevada.
Carlson et al. (2011) presented a map showing red fox detections (through 2007) in Lassen, Tehama, Shasta, Siskiyou, and Modoc counties, California. In August 2010, biologists on the Humboldt-Toiyabe National Forest detected a red fox at an automatic camera station near the Sonora Pass along the border of Tuolomne and Mono counties (Perrine et al. 2010). Preliminary genetic analyses conducted at UC Davis indicated that the fox was a Sierra Nevada red fox. Further surveys and analyses were planned. No confirmed recent records exist for elsewhere in the historical range in California, despite fairly widespread use of appropriate survey methods (e.g., baited "camera traps") (Perrine et al. 2010). Status of this subspecies in Oregon is unknown (Perrine et al. 2010).