NATURAL HISTORY

SIERRA NEVADA RED FOX } Vulpes vulpes necator
FAMILY: Canidae

DESCRIPTION: Sierra Nevada red foxes have a small, slender body and legs; long, pointed ears; an elongated snout; and a long, white-tipped tail. They’re 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. These foxes occur 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: Sierra Nevada red foxes live 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: Sierra Nevada red foxes historically ranged from Tulare Country northward through California's Sierra Nevada Mountains and the Cascade Mountains of Northern California and Oregon. Now the foxes remain 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. There are unknown numbers in the southern Cascades in Oregon — that population is thought to be small.

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 foxes are believed to be monogamous. The gestation period is between 52 and 54 days, and pups are born in early to mid-April, moving outside the den by June but not very mobile until later in the summer. Sierra Nevada red foxes’ 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: Sierra Nevada red foxes hunt 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. They also eat fruit and carrion.

THREATS: The foxes are threatened by habitat destruction through logging, grazing, fire suppression, offroad and over-snow vehicles, road building and other human development. They also face dangers from poaching, predation, disease, genetic vulnerability and climate change.

POPULATION TREND: While the exact population of Sierra Nevada red foxes 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 40 individual foxes — or even fewer than 20 — remain.

Photo of Sierra Nevada red fox by Keith Slausen/Wikimedia.