(CN) – The U.S. Fish and Wildlife Service proposed listing the Sierra Nevada red fox as endangered Tuesday, given there are fewer than 100 animals left in its namesake mountain range.
“The service determined the Sierra Nevada (distinct population segment) of the Sierra Nevada red fox is at risk of extinction due to a variety of factors, including the effects of small population size and continued hybridization with non-native red foxes,” said Fish and Wildlife spokesperson Meghan Snow.
The genetically distinct subspecies of the red fox was thought to be locally extinct in all the Sierra Nevada range until 2010, when a small population was discovered near Sonora Pass about 46 miles south of South Lake Tahoe.
Despite the discovery, the subspecies’ population numbers are exceedingly low.
“I’d say there is about 20 breeding pairs of mountain red foxes in all of California,” said John Perrine, a biology professor with California Polytechnic State University, who has studied the subspecies for years.
When Perrine began writing about the Sierra Nevada red fox in the 1990s, the only population in California lived near Mt. Lassen at the southern end of the Cascades.
But during a survey conducted by the U.S. Forest Service, someone captured a blurry picture of what biologists believe could only be a red fox in the mountainous area between Lake Tahoe and Yosemite National Park.
Then Benjamin Sacks and Cateline Quinn, two biologists from the University of California, Davis, placed trail cameras and after taking hair and dung samples from the area confirmed the presence of the Sierra Nevada red fox.
“We were able to reconstruct pedigrees, see what individuals were in attendance, who was breeding with whom and the minimum number of pups produced per year,” Sacks said. “It was an unfolding drama that we discovered by picking up poop.”
In 2015, a Sierra Nevada red fox was spotted in Yosemite National Park for the first time in more than a century.
While there is evidence the Sierra Nevada red fox is doing better now than in the previous two decades, the proposed listing will help, the scientists said.
“Anytime you have a listing, it will bring money and attention that allows us to do surveys,” Perrine said.
Sacks gave credit to the Center for Biological Diversity, the wildlife advocacy organization that first petitioned the U.S. Department of Fish & Wildlife in 2011 to list the subspecies.
The center celebrated the proposed listing Tuesday, saying it was vital to protect habitat that facilitates the rebound in the fox population in the mountains of California.
“Protecting the Sierra Nevada red fox could provide a welcome lifeline for a vanishing emblem of remote Sierra wilderness,” said Jeff Miller, a conservation advocate at the center.
While habitat degradation is certainly one possible factor, there is scant information on how and why the fox went from roaming widely throughout the Sierra Nevada to nearly vanishing.
“No one knows, but my suspicion is that the level of trapping was simply too high considering the density of mountain red foxes,” Sacks said.
While the common red fox will typically establish a range of 1 to 2 miles, the mountain red fox will roam as far as 18 miles. The low density means if a few individuals are killed, it has a greater effect on the distinct population.
California has banned trapping of the species.
Other threats include poisoning, livestock grazing and disturbance from off-road vehicles.
Fish and Wildlife will gather public comment along with the latest available science until March 9, at which point the agency will decide whether to list the species.
The Sierra Red Fox is morphologically similar to the common red fox found throughout North America but is genetically distinct. The mountain foxes have thicker coats are much smaller, with larger more hairy feet that helps them stay aloft while traveling through snowdrifts.
The animal can be red, black or cross-colored and are distinguished by a white-tipped tail and black-backed ears.
They feed on smaller mammals, birds, insects and fruit.