The Sierra Nevada red fox (Vulpes vulpes necator ), also known as the High Sierra fox, is a subspecies of red fox found in the Oregon Cascades and the Sierra Nevada. It is likely one of the most endangered mammals in North America. The High Sierra fox shares most of its physical characteristics with the red fox, though it is slightly smaller and has some special adaptions for travel over snow. The High Sierra fox was discovered as a subspecies in 1937, but its study lapsed for more than half a century before its populations were rediscovered beginning in 1993. This subspecies of red fox may live up to 6 years.
Like other montane foxes, Sierra Nevada red foxes are somewhat smaller and lighter in weight than lowland North American red foxes. Their fur may be red, cross, or silver phase with the red phase having the greyish-blonde coloration characteristic of montane foxes. All three phases occur in the Oregon Cascade and Sonora Pass populations, but only red phase individuals have been found in the Lassen population. Their foot pads are fur-covered, a common adaptation to travel over snow. Sierra Nevada red foxes are relatively long-lived compared to other red foxes, typically living five to six years. Non-invasively monitored females have either not bred or bred a minority of years.
The extent of the Sierra Nevada red fox populations is an area of active research. In Oregon, ongoing studies at Mount Hood and Central Oregon were prompted by observations in 2012 and 2013. Recent genetic evidence also suggests range expansion into western Oregon since the 1940s. In California, detections occurred in northern Yosemite National Park the winter of 2014-15, the Stanislaus National Forest in late 2015, and in Lassen Volcanic National Park in 2018. The first two areas are near Sonora Pass, but it has not been confirmed the individuals are part of the Sonora Pass population.
A 2005 study of the then remnant population surviving on Mount Lassen found that the foxes are nocturnal hunters whose diet is predominantly mammals, especially rodents and mule deer, supplemented by birds, insects and pinemat manzanita berries as seasonally available. Lagomorphs (hares, rabbits and pikas) were virtually absent from the foxes' diet.
Documented trapping of the Sierra Nevada red fox may have begun when Moses Schallenberger of the Stephens-Townsend-Murphy Party spent the winter of 1844-45 at Donner Pass, taking an average of one red fox every two days. Red fox fur was sought after by trappers during the early part of the 20th century because it was softer than that of California’s gray fox (Urocyon cinereoargenteus ). The State of California banned trapping of Sierra Nevada red foxes in 1974 and listed the subspecies as threatened in 1980.
The fox's Sierra Nevada Distinct Population Segment is estimated at 29 adults near Sonora Pass in California. The Southern Cascades Distinct Population Segment consists of an estimated 42 adults near Lassen Volcanic National Park and an unknown number of individuals in five areas of Oregon. No other populations are known. Interbreeding with non-native red foxes and recruitment success are primary conservation concerns.
The fox is a data gap species in Oregon and designated an Oregon sensitive species by the U.S. Forest Service. Listing of the Southern Cascades Distinct Population Segment was found to be not warranted. The Sierra Nevada Distinct Population Segment was listed under the Endangered Species Act in 2021.
