Fox Populi: Near-Extinct Species Makes a Comeback on CA Islands

A Santa Cruz Island Fox. | Photo: Courtesy The Nature Conservancy

Christie Boser carefully reaches into the trap and pulls out the fox with one hand. A young male, the housecat-sized animal is surprisingly calm -- considering he's a wild animal. As his eyes dart around the small crowd gathered in the dry riverbed, Christie, a biologist with The Nature Conservancy, fits a tiny hood over his eyes to keep him calm. Over the next few minutes, Boser gives the fox a mini check-up -- teeth, coat, testes.

"10 years ago, finding healthy young male foxes would never have been possible," says Tim Coonan, a biologist with the National Park Service at Channel Islands National Park.

That's because the fox population on all the Channel Islands dipped precipitously low in the late 1990s. The fox comeback is a success story that could be applied to other places.

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The story of conservation isn't always a simple one. Before it was part of a national park, farmers brought pigs to Santa Cruz Island, and they became wild -- "roto-tillers" as Coonan calls them -- causing damage to both environment and culture, digging up archeological sites, eroding the soil, and spreading invasive weeds. Their piglets also attracted another new creature: golden eagles. After the islands' bald eagle population declined due to DDT in the water, golden eagles moved in to prey on the abundant porcine feast, and then they moved to preying on foxes.

The fox population, once measured at 1,400, dropped to below 70 on Santa Cruz in 2000, the largest of the Channel Islands. San Miguel and Santa Rosa also experienced catastrophic fox losses around the same time, but have since recovered as well.

National Park Service and The Nature Conservancy share ownership of Santa Cruz Island (TNS owns about 75% and the parks own about 25%) and together they began to trace the signals on fox radio collars to golden eagle nests.

Once the biologists had pinpointed the cause of the drop in fox numbers, they formulated a plan. They called in hunters to remove the 5,000 feral pigs from the island. Then they relocated 44 golden eagles to Northern California, tracking them to make sure they stayed put and thrived in their new homes. "The day the final pair of eagles was captured, we were dancing around the room," recalls Boser.

Christie Boser, biologist with The Nature Conservancy, holds up a trap with a young male fox inside. Island foxes weigh only about 4 pounds and are the size of housecats. | Photo: Katherine GammonIn addition, the groups started a captive breeding program for foxes to bolster their numbers. 35 foxes were paired according to their genetic makeup, in order to preserve as much diversity as possible. The breeding program turned out 250 foxes in a matter of years, and stopped five years ago.

The fox and the island

Even foxes weren't initially native to the channel islands. Their ancestors, the grey fox, were brought over by the Chumash people to the islands (the Channel Islands themselves represent the first evidence of human seafaring in the Americas) around 6,000 years ago -- or perhaps they floated over on driftwood or mats of vegetation from the mainland.

In any case, there aren't any fossils of fox bones in the kitchens of Chumash sites; instead, the foxes appear to have held a sacred place in Chumash society, says Coonan.

"It's an amazing story of rapid evolution. Each of the islands has a distinct population of foxes and they even look different. Any employee knows that that you're more likely to get bit on San Miguel Island where the foxes have a shorter tail but longer mouth," Coonan notes. So even though foxes weren't native to the island in a traditional sense, it was a "no-brainer to remove the eagles and restore the fox population," he says.

Island ecosystems are weird and wonderful across the world. They represent 40% of extinctions worldwide, while only making up 4% of global land mass. When mainland animals arrive on islands, they change to their environment -- small animals get big, while larger animals become tiny. During the history of the Channel Islands, they were home to pygmy mammoths, dwarf rattlesnakes, and a giant Pleistocene mouse.

Today, there are 60 species of animals and plants unique to the islands, and 12 that only exist on Santa Cruz itself, an island just 96 square miles big.

"No one thought this recovery would have happen as fast as it's happened," says Kate Faulkner, Chief of the Resources Management Division at Channel Islands National Park. As the golden eagles departed, bald eagles were brought back in (they choose marine life over foxes to eat) and 40 birds now inhabit the northern Channel Islands.

There are still efforts to monitor the health and numbers of the special wildlife and plants on the islands, and the biologists say that that diseases like distemper brought in from dogs is a serious concern -- which is why canine buddies aren't allowed in the park.

Less than a decade after four of the six island fox subspecies were listed as federally endangered, the biologists believe they are close to meeting criteria for delisting -- and the lessons of the island fox could be applied to other efforts aimed to recover species on the brink.

Faulkner points to the interdisciplinary expertise and multi-faceted approach of the Park Service and The Nature Conservancy. Boser adds that humans were able to create the conditions -- removing eagles and pigs -- that enabled the foxes to rebound on their own.

Christie Boser checks a fox's teeth; this male has a chipped front canine, which isn't uncommon in males trying to find their own territory. | Photo: Katherine Gammon

Back at the checkup, Christie Boser removes the green hood that kept the tiny fox calm as she examined him. He creeps away down the road, and in a moment, he disappears into the sagebrush. He passed the checkup successfully, just like recovery of his species.

Never been to Channel Islands National Park? Start with KCET's guide.

About the Author

Based in Santa Monica, Katharine Gammon is a freelance science writer who writes for a wide range of magazines covering innovation, society, and animal science.
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