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NATURAL HISTORY

SIERRA NEVADA RED FOX } Vulpes vulpes necator
FAMILY: Canidae

DESCRIPTION: The Sierra Nevada red fox has a small, slender body and legs; long, pointed ears; an elongated snout; and a long, white-tipped tail. It is typically smaller than lowland red fox subspecies, with males weighing up to 9.2 pounds and measuring up to 3.4 feet long and females up to 7.7 pounds and 3.2 feet. This fox occurs in three genetically determined color phases: red, black/silver and cross. In the red phase, a reddish-brown upper body contrasts with white cheeks, chin, throat and abdomen. In the black/silver phase, which varies from silver to black, silver guard hairs afford a “frosted” appearance. The cross phase, which is dominant among Sierra Nevada red foxes, exhibits characteristics of both the red and the black/ silver phases.

HABITAT: The Sierra Nevada red fox lives in a wide range of remote, high-elevation alpine and subalpine habitats, including meadows; dense, mature forest; talus; and fell fields. Habitat use varies seasonally.

RANGE: The Sierra Nevada red fox historically ranged from Tulare Country northward through California’s Sierra Nevada Mountains and the Cascade Mountains of Northern California and Oregon. Now the fox remains in two small California populations: one near Lassen Peak, with likely fewer than 20 known foxes, and a second near Sonora Pass on the Humboldt-Toiyabe and Stanislaus national forests, with only three known foxes.

MIGRATION: Sierra Nevada red foxes are seasonal elevational migrants, moving from alpine and subalpine habitats in summer down to mid-elevation habitats in winter.

BREEDING: Sierra Nevada red fox breeding occurs between December and March. Mating and den construction occur in January and February; the fox is believed to be monogamous. Its gestation period is between 52 to 54 days; pups are born in early to mid-April, moving outside the den by June but not very mobile until later in the summer. The Sierra Nevada red fox’s relatively low reproductive capacity makes recovery from population decline more difficult than for other foxes.

LIFE CYCLE: Red foxes are estimated to live two to four years in the wild, though no longevity data have been collected for the Sierra Nevada red fox specifically. Sierra Nevada red fox pups reach sexual maturity in their first year.

FEEDING: The Sierra Nevada red fox hunts at dusk and during the night, feeding on a variety of prey — primarily rodents and other small mammals, birds and reptiles — according to the season. It also eats fruit and carrion.

THREATS: The fox is threatened by habitat destruction through logging, grazing, fire suppression, off-road and over-snow vehicles, road building and other human development. It also faces dangers from poaching, predation, disease, genetic vulnerability and climate change.

POPULATION TREND: While the exact population of the Sierra Nevada red fox is unknown, a rapid reduction in its size over the past century is likely to have corresponded to sharp range contractions witnessed during the same period, as well as genetic evidence of decline. Likely fewer than 50 individual foxes — or even fewer than 20 — remain.
Sierra Nevada red fox photo by Keith Slausen, U.S. Forest Service