Home & Garden Columns

Wild Neighbors: The Wrong Fox and Other Reversals of Fortune

By Joe Eaton
Tuesday July 03, 2007

This is not strictly a Berkeley or Bay Area story, although it begins here with the introduced red fox (Vulpes vulpes regalis). You probably know the basics: eastern and Canadian foxes brought to the Central Valley during the 19th century by would-be fur farmers, some escaping and taking to the wild where they’ve become serious predators on a roster of endangered species.  

Red foxes were first sighted in the South Bay in 1986, about the time the California clapper rail population began to crash. The light-footed clapper rail of Southern California was similarly decimated. The foxes will also take western snowy plovers, California least terns, Caspian terns, gulls, shorebirds, and herons, and they prey on their smaller relative, the San Joaquin kit fox. 

Unlike most native mammalian predators, introduced red foxes don’t mind getting their feet wet. They’ll kill more than they can immediately eat and cache the surplus. What to do about foxes in the Bay’s tidal marshes has become a cause celebre between animal-rights types and genuine conservationists. 

But there’s another, less notorious fox that’s a California native: the Sierra Nevada red fox (Vulpes vulpes necator), shy, elusive, and vanishingly rare. Unlike the introduced type, this fox isn’t always red: it comes in “black,” “silver,” and “cross” color morphs. No one is really sure how many Sierran foxes are left: it’s possible the only survivors are in the Mount Lassen area. 

It used to be assumed that any red foxes below the 3000-foot line in the Sierra were part of the introduced population; above that, likely natives. That held up until Ben Sacks at UC Davis’s Veterinary Genetics Laboratory began looking closely at California’s red foxes. He was interested in patterns of gene flow between different fox sub-populations and whether they were self-sustaining. And he had occasion to look at a lot of museum specimens collected along the coast and up and down the Valley. 

Sacks found something unexpected: the foxes of the Sacramento Valley were more like the native necator than the introduced regalis. The frontier between those foxes and the aliens appears to lie along the Delta and the American River. He also found records of red foxes north of that line dating to before the fox-farming area.  

Were these Sierra Nevada foxes that had adapted to the hot, dry flatlands, or a distinct indigenous population? It appears to be too soon to tell, but Sacks is still looking for data. Anyone who spots a fox in the Sacramento Valley, dead or alive, is asked to report their findings at foxsurvey.ucdavis.edu. 

All this has interesting wildlife management implications. Animals once considered pests—threats to other wildlife—may now have to be treated as an endangered species, or at least a distinct population segment. But science can cut both ways. 

Consider the plight of the Guadeloupe raccoon. Mammalogists used to recognize three island-endemic species of raccoon in the West Indies: on New Providence Island in the Bahamas, Guadeloupe, and Barbados, the last now extinct. As the only presumed-native carnivores in the Caribbean, they were always something of a mystery. They looked more like the familiar North American raccoon than the South American crab-eating raccoon, which would have been the more probable parent species. And their bones never showed up in fossil deposits or pre-Columbian archeological sites. 

But they were considered natives in good standing, and the Bahama and Guadeloupe species were declared endangered. The Guadeloupe raccoon, in fact, became the flagship species of local conservation programs and the island’s national park system.  

Then in 1999 came a DNA study reporting no differences between the Guadeloupe raccoon and the North American stock. 

Four years later, Don Wilson of the Smithsonian’s National Museum of Natural History and Kristofer Helgen of Harvard’s Museum of Comparative Zoology examined museum specimens of island and mainland raccoons, and concluded that what were supposed to be distinctive traits of the Bahama, Guadeloupe, and Barbados raccoons also occurred in Georgia and Florida populations. The island raccoons had apparently—who knows why?—been introduced, as had a whole Barbadian zoo of mongooses, green monkeys, and camels. 

Helgen and Wilson also pointed out the damage these critters could do by raiding the nests of endangered ground-dwelling birds and digging up the eggs of endangered sea turtles. I don’t know whether the raccoons’ own endangered status has been revoked, but it’s surely only a matter of time and bureaucratic process. 

A cautionary tale, in any case. In the harsh world of conservation biology, you’re only as good as your last genetic study.