TRUCKEE, Calif. — Native or non-native? That is the question for wildlife biologists regarding a potentially endangered red fox seen hanging around Donner Lake the past week.

Reddish-orange in color and lanky in shape, with a long, bushy tail, the fox was first reported to the California Department of Fish and Wildlife on Thursday, Oct. 31. It has since been spotted on several occasions along the north shore of the lake, as recently as Monday.

“If this does prove to be a native, endangered Sierra Nevada red fox, that would be very exciting to us, because we don’t have very many of those, and we don’t really know of a population in the Tahoe area at all,” said David Wright of the California Department of Fish and Wildlife, who added that there may be fewer than 50 Sierra Nevada red foxes in existence.

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“It’s very hard to put a population estimate on it. But based on the handful of foxes in the Lassen area and the handful that we can estimate in the Sonora Pass area, we’re talking about a very small population — one of the most endangered species in the state.”

Despite studying photos of the animal, wildlife biologist Dr. Ben Sacks of the University of California, Davis, said a DNA test is required to determine whether it is a non-native red fox from the lowlands of California or the rare Sierra Nevada red fox.

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Both foxes usually display the same physical characteristics — namely large, white-tipped tails and black markings behind the ears, as well as black legs, he said.

“I was very, very excited to see the photos, but I’m apprehensive,” Sacks said. “I’m concerned that it could be introduced or a non-native one. But I’m mostly excited and optimistic.”

Upon learning of the fox on Monday, Sacks sent PHD grad student Cate Quinn to Donner Lake to collect DNA samples. Quinn is currently studying the Sonora Pass population of the Sierra Nevada red fox. The samples she gathered — hairs, scat and a chewed pine cone — will undergo DNA testing at UC Davis to determine the species.

Sacks said the initial testing should take about a week and will show the DNA passed on from the animal’s mother only. If the mother proves to be a Sierra Nevada red fox, Sacks said more involved testing will be carried out to determine the genetics of the father, as Sierra Nevada red foxes and non-native red foxes can mate and create hybrids.

“In order to figure out whether it’s a bona fide, full-on indigenous fox, we’d need to look at nuclear DNA — the stuff from the mom and dad — and that will take longer because the data analysis takes a little bit of doing,” he said. “By next week we should know, assuming we’ll be able to get good DNA, which I think we should.”

Wright said the Sierra Nevada red fox was once abundant throughout the Sierra and even into the Cascades. Because of their fine pelts, however, trappers severely cut into their numbers to the point of near extinction.

“There was also a period of time when many, many carnivores were poisoned,” Wright said.

The similar non-native red fox, meanwhile, was brought to the Western United States from Alaska and Canada in the early 1900s, Sacks said — contrary to the belief that they are native to Europe. They were placed in fox farms throughout the West when the fur industry was booming.

But when the industry slowed, and eventually faded completely by the 1970s, farmers turned many of the foxes loose, Sacks said. As a result, the non-native red foxes are relatively common in the Western states, including the lower elevations of California.

That’s far from the case with the Sierra Nevada red fox. Quinn said a small population of the indigenous fox — known to be lankier and with larger teeth than the native gray fox — was discovered in the Lassen Volcanic National Park area north of Truckee in the early 2000s.

Another population near Sonora Pass, south of Lake Tahoe, was discovered in 2011. Both populations are estimated at around 20 individuals, Quinn said.

“This would be huge to find out that there’s another population that has been here all along,” Quinn said. “I’m holding my breath and waiting to see what happens.”