Truckee red fox may not be native
November 15, 2013
It's a red fox, all right.
An endangered Sierra Nevada red fox? Probably not.
After the first step of DNA testing, wildlife biologists from the University of California, Davis, determined that the fox seen near Donner Lake in recent weeks contains the genes of a non-native red fox in its maternal line — as opposed to the highly endangered Sierra Nevada red fox, of which there may be fewer than 50 remaining.
"It's not a good sign," said Dr. Ben Sacks of UC Davis, who studies fox populations along with grad student Cate Quinn. "The fact that it shows non-native is discouraging. But we don't want to jump to any premature conclusions about the fox."
The fox in question was first reported to the California Department of Fish and Wildlife on Thursday, Oct. 31. It has since been seen on multiple occasions along the north shore of the lake.
Quinn, who is currently studying one of only two known populations of the Sierra Nevada red fox, near Sonora Pass, collected scat, hair and saliva samples from the animal last week. The mitochondrial DNA from the scat showed maternal genes from a non-native red fox, which are common to the San Joaquin Valley and foothills but are not known to venture into the Sierra Nevada.
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Sacks said the mitochondrial DNA, which determines female lineage only, could trace back to the previous generation or many generations back. If the female, non-native red fox genes that were discovered prove to be many generations removed, a small chance remains that the animal is close to a 100 percent indigenous Sierra Nevada red fox.
"It could be a first-generation hybrid, which, from a management point of view, is essentially a non-native — maybe worse, because it means that there are some non-natives maybe circulating through the native populations," Sacks said. "But if it's sort of a multi-generational back cross, then really for all intents and purposes, it's native. It could be essentially 100 percent native … and at some point there was some non-native introgression."
In order to make that distinction, Sacks said the animal's nuclear DNA — from both the males and females in its family line — will be tested as well, which is a more involved process and could take a month or more.
While no one knows how the fox arrived at Donner Lake, where it seems comfortable and relatively undaunted by human activity, Sacks said it may have wondered up from the valley along the Interstate 80 corridor or was brought to the area by someone.
"They're pretty solitary. If this fox made its way up there on its own, or was dropped off, my guess is that it's all by itself — because as far as we know, there are no other foxes in the area," Sacks said, adding that his biggest concern is that the fox, if truly non-native, might find one of the small pockets of indigenous Sierra Nevada red foxes and interbreed. "If he starts to get especially disappointed (in not finding a mate) and starts wondering, he might well find the population 50 miles to the south. And that would be a problem. There are many kinds of negative genetic affects from taking a non-native individual and introducing it to a small, endangered gene pool.
"But I think at this point we just don't know enough."