Cameras reveal new Sierra Nevada fox population in Calif.

Wildlife managers have discovered a previously unknown population of potentially endangered foxes high in the mountains of California, according to preliminary results presented in a poster session at the 2019 Joint Annual Conference of the American Fisheries Society and The Wildlife Society in October.

But the small population of Sierra Nevada red foxes (Vulpes vulpes necator) brings concerns about the newly discovered population’s viability.

The foxes tend to prefer high altitude habitat along mountain ridges. Courtesy Brian Hatfield

“All the populations that are known about in California are small. There are definitely concerns about inbreeding, and there’s been fairly well documented inbreeding depression in small populations,” said TWS member Brian Hatfield, an environmental scientist with the California Department of Fish and Wildlife.

Sierra Nevada red foxes have existed historically across Oregon and California. Currently they are mostly found in Oregon’s Cascade Mountains, with a only two small California populations at Lassen Volcanic National Park and Sonora Pass. They are currently being considered for listing under the Endangered Species Act.

Hatfield and his colleagues have been involved in a project that started in 2015 to survey for the elusive species between Kings Canyon and Yosemite National Park by using camera traps and collecting scat.

They placed the camera traps at high altitudes along the crest of the Sierra Nevada in areas. But it wasn’t until 2018 that the camera traps revealed a newly discovered fox population at Mono Creek. Follow-up scat analysis revealed at least three individuals in the population, including two females and a male, according to the poster presentation by Hatfield’s colleague Liz Siemion, a scientific aid with CDFW and a TWS member.

But finding more information about the population has proven difficult.

“They are very secretive even when you find them,” Hatfield said. “A fox will come into our camera and see the infrared or hear the camera and just run away.”

But the recent discovery shows that there may be more foxes in the mountains than researchers previously thought. Or, it may be that they range more widely than previously believed — the male fox detected in this new population had previously been detected about 62 miles away at Sonora Pass during past monitoring.

The situation is ‘very dynamic,’ Hatfield said, noting that the Sonora population was only discovered in 2010.

“The survey effort that’s ongoing is just really basic questions of presence and absence,” he said. But the results of the study will help larger conservation efforts for the Sierra Nevada populations.