Yosemite National Park’s wildlife biologists monitor commonly seen mammals like mule deer, bobcat, and coyote, but they focus heavily on animals listed as endangered or threatened in order to ensure their long-term survival. Of Yosemite’s special status mammal species, the Sierra Nevada bighorn sheep and the Pacific fisher are listed under the U.S. Endangered Species Act, and 14 are protected by the state of California.

Sierra Nevada Red Fox: State Threatened

• Endangered Status: State threatened
• Physical description: Dark-colored fur compared to other red fox
• Den: In rock outcrops, hollow logs and burrows in soil
• Preferred Range: Approximately 6,000 feet in elevation
• Behavior: Shy, perhaps avoiding human encounters

Slightly smaller and darker than the introduced lowland population of red foxes, the Sierra Nevada red fox (Vulpes vulpes necator) is one of two native species of fox in Yosemite. The first documented photographs of the Sierra Nevada red fox were taken during a 1990 study of another animal, the wolverine, that used remote, automatic cameras and happened to capture an image of a Sierra Nevada red fox.

Due to rare sightings, relatively little is known of the life history of the Sierra Nevada red fox, but it is assumed that its habits are similar to those of other red foxes regarding den choice, hunting tactics, and breeding behavior. They may move pups to a new den several times, for example.

The fox’s range is from the Cascade Range east to the Sierra Nevada and then south along the Sierran crest to Tulare County. Recent research in the late 1990s highlighted the only known population: 10 to 15 individuals in the Lassen Peak vicinity, which is in Lassen Volcanic National Park, north of Yosemite National Park. Theyinhabit remote areas of the state where chance encounters with humans are uncommon. Some scientists have come to the conclusion that Sierra Nevada red fox likely never occurred in large numbers, relying on references in Joseph Grinnell’s Furbearers of California in 1937. During the 1940s and 1950s, trappers collected 135 pelts and that number shrunk to just two pelts a year by the 1970s. The state of California banned Sierra Nevada red fox trapping in 1974 and added the animal to the state-threatened list in 1980, where it remains today. The numbers of native fox decline while non-native red fox populations increase and compete for food, particularly in the Central Valley.

Sightings of the subspecies range from 5,000 to 7,000 feet in elevation with extremes placed at 3,900 feet in Yosemite Valley and 11,900 feet at Lake South America in the southern Sierra Nevada. You would be most likely in summer to see a Sierra Nevada red fox above 6,000 feet in the subalpine zone, amongst the red fir and lodgepole pines, and alpine fell-fields.

Sadly, threats to the Sierra Nevada red fox are unknown. In 1997, a Sierra Nevada red fox study using remote cameras began. A young male fox was captured and radio-collared in late 1997 and a female fox was likewise captured and collared in early 1998. These were the first individuals of this species ever captured and radio-collared in California.

Wolverine: State Threatened

• Endangered Status: State threatened
• Physical description: Brown with a pale stripe across the top of head and down the side of body
• Size: Largest member of the weasel family at 26 to 34 inches in length and 24-40 pounds
• Territory: May travel extensively over a multi-state range
• Behavior: Fierce predator that will attack larger, wounded or weak animals
• Population: Unknown if any exist in California

If you ask Yosemite National Park scientists the status is of the wolverine in the park, they will reply that they just don’t know. Evidence of wolverines (Gulo gulo) in California has not been scientifically verified since the 1920s. The last confirmed Sierra wolverine was shot as a specimen in 1922.  Rumored sightings occur every year in Sequoia National Park, just south of Yosemite, and in the northern part of the state. The California Department of Fish and Game lists the wolverine as present but threatened. The department indicates receiving about 150 sightings of this largely nocturnal animal during the past several decades, typically at about 8,000 feet in elevation.

Excitement rippled through the California scientific community in late February of 2008 when a wolverine was photographed in the Tahoe National Forest while an Oregon State University student conducted research on pine martens with a remote-controlled camera. DNA tests of collected scat samples, however, prove the animal is related to wolverines in the Rocky Mountains rather than historic California specimens found only in museums. How the photographed wolverine got to California is unknown, but the species frequently travels long distances. One wolverine in Wyoming fitted with a tracking collar, for instance, covered 543 miles over 42 days before its collar fell off.

The North American wolverine resembles a small bear and acts as fierce as a grizzly. Their jaws are very powerful and are adapted to crush and shear frozen meat and bones. Wolverines subsist on a variety of foods including small- and medium-sized mammals, birds, insects, berries, and fungi. Carrion, especially in the form of large ungulates, is believed to be an important component of the diet, particularly during winter.

Wolverines, which have disappeared from almost half of their North American range, are found primarily in Washington, Montana, and Idaho. Historically, wolverines occurred in the remote and high-elevation areas of California, ranging from the northwestern part of the state to the southern Sierra Nevada. Studies have mapped some of reported sightings in Yosemite and Sequoia-Kings Canyon national parks. Wolverines, it’s believed, were probably never numerous in California due to their extensive home range size and small amount of suitable habitat in the state. Renowned scientist Joseph Grinnell suggested in 1937 that fur trappers might have reduced wolverines to as few as 15 pairs by the 1930s.