The Channel Islands, off the coast of Southern California, are the only home of a species of tiny fox that looks like a plush toy. How the island foxes got there from the mainland is up for debate — maybe with Native Americans, maybe on storm debris. But fossils show they’ve lived on the islands for many thousands of years.

Along the way, these descendants of mainland gray foxes evolved into four-pound “island dwarves” whose size was better suited to survival in their isolated habitat with its slim resources. Though they are omnivores the size of a cat, in this environment they were long the top predators. They ate lizards, birds, deer mice and plants.

The foxes’ decline started when 19th-century settlers brought livestock to the islands and some of their pigs escaped. The feral swine attracted golden eagles, which dined on piglets and saw the little foxes as excellent snacks. The petite canines had never evolved defensive instincts, and predator was now prey.

“They have this naive, adorable little personality,” said Christina Boser, the Nature Conservancy’s island fox ecologist. “They’re not really scared of people,” let alone raptors, she said.

The foxes on one island, Santa Catalina, were also ravaged by canine distemper brought by dogs. In this out-of-whack ecosystem, the foxes’ numbers on the four islands plummeted to fewer than 200 by the late 1990s, a drop of 90 percent. In 2004, they were declared federally endangered

But just 12 years later, the U.S. Fish and Wildlife Service on Thursday announced that the foxes of San Miguel, Santa Rosa and Santa Cruz islands had so rebounded that they were being taken off the endangered species list. That makes them the 37th species ever removed from the list due to recovery — and the protagonists of the fastest mammal recovery in the Endangered Species Act’s 43-year history. The Santa Catalina island fox was downlisted to threatened.

“It shows that we can do recovery,” Dan Ashe, director of Fish and Wildlife, said in an interview this week, adding that the Obama administration has delisted 19 species. “Here you have an example of one that, for mammals, is getting off the list in record time due to a lot of collaboration.”

Ashe was referring to critical comments about the Endangered Species Act, one of which is that many plants and animals seem to be permanent residents on the list. Other detractors say it takes too long for at-risk species to get on the list, a case biologists make in a new study that found the process takes an average of 12.1 years.

The island ecosystem that facilitated the foxes’ rapid downfall also made their recovery simpler than it might be for mainland species. They were also beneficiaries of intense cooperation between groups including the National Park Service, which manages five of the islands, and the Nature Conservancy, which owns most of Santa Cruz.

The recovery effort involved trapping and captive-breeding the foxes on the islands, which are 12 to 70 miles off coast, so as not to expose them to mainland parasites. Between 2005 and 2006, more than 5,000 feral pigs were killed using helicopters, snipers, traps and dogs, the Los Angeles Times reported in 2007. The predatory golden eagles were trapped and relocated to the mainland. Bald eagles, which had lived on the islands before being wiped out by DDT poisoning, were brought back. (Fortunately for the foxes, those eagles like to eat fish.)

By 2008, more than 230 captive-bred foxes had been released into the wild, Ashe said, and they reproduced magnificently. Today, there are nearly 6,000 foxes on the four islands.

Boser, who began working on Santa Cruz in 2006, said that there was a time when the traps she set for monitoring purposes hardly ever caught a fox.

“I was out there last week and put down 10 traps and caught nine foxes,” she said. Before, she added, “you took a picture with a fox, because this was a rare thing and this was exciting. Now you’re seeing them on the roads and the fields and all over the place.”

Today, Boser said, the biggest threat is disease. Although visitors are prohibited from bringing dogs to Santa Cruz, “we see dog poo on the beaches,” she said, so all the foxes must be vaccinated against rabies and canine distemper. Dogs are also the reason the Santa Catalina foxes are still listed as threatened — pooches are allowed there, so the chance of another epidemic remains, Fish and Wildlife said.

Boser called the foxes’ comeback “totally exciting,” but she said there’s more to be learned from the animals. Researchers have found that the foxes are the least genetically diverse reproductive species ever studied. Knowing more about how this affects their fitness in an isolated place with so few resources, Boser said, could hold lessons for mainland species that live in island-like habitats, such as the mountain lions of Los Angeles’ Santa Monica Mountains.

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