Editor's note: This is a sidebar to "Hostile Takeover."
The Channel Islands, a chain off the coast of Santa Barbara, illustrate just how much a non-native species can roil the ecology of a place, changing predators into prey and throwing unfamiliar species into competition. During the 19th century, settlers brought pigs to the islands. Some of those pigs escaped. More than 100 years later, the prospect of tasty piglets lured golden eagles from the California coast. The previous resident raptors, bald eagles, disappeared in the 1960s when DDT made their eggs too fragile to survive, and during the 1990s, golden eagles moved into their old haunts. While the bald eagles found most of their prey in the water, the golden eagles searched on land.
The islands host a unique species of fox, a diminutive version of the gray fox found on the mainland. One of the smallest canids, the Channel Island fox weighs roughly four pounds and stands a foot high. If domesticated, it would be a tawny lapdog. Six of the eight islands have their own subspecies, distinguished by the number of bones in their tails. When piglets were in short supply, the golden eagles feasted on the foxes.
Within 10 years of the arrival of golden eagles, the number of adult Santa Cruz Island foxes had plunged from 1,500 to less than 100. San Miguel Island foxes went extinct in the wild. So did Santa Rosa Island foxes, persisting only in captive breeding facilities. In 2004, four of the subspecies were listed as endangered.
Although disease and invasive weeds in fox habitat were thought to contribute to the decline, it was pretty clear that the golden eagle was the main culprit. Most of the eagles were caught and released on the mainland, but a few outwitted all pursuers.
A 2003 article in Science titled "Removing Protected Populations to Save Endangered Species" made the case for "lethal removal" of the eagles. Even though the eagle was shielded by the Migratory Bird Treaty Act and the Bald Eagle and Golden Eagle Protection Act, the secretary of the Interior could make exceptions. The article's authors predicted that if the Park Service killed all the pigs and couldn't catch all the eagles that the foxes would be eaten to extinction.
For ecologist Josh Donlan, director of the nonprofit Advanced Conservation Strategies, there was no question that the last few eagles should be shot. Donlan works frequently on islands, where interventions are often aggressive. He tells the story of Anacapa Island, a Channel Island whose tiny size and rocky face made it inhospitable to foxes. Non-native black rats were the problem there: The Park Service feared they were eating the eggs of the rare Xantus murrelet (named for the same Xantus who gave the spotted owl its Latin binomial), preventing it and other birds from nesting. After taking populations of the native deer mice into captivity and relocating most raptors, the Park Service spread rodent poison, knowing that some falcons, owls and hawks would die from eating the toxic rats. Once the rats were gone, biologists replaced the raptors and the native rodents, and now seabirds have settled in.
"Managers and society in general need to come to terms with the fact that our natural parks are managed. Some of that management is going to call for culling or reducing native species. That's just part of the world we live in," said Donlan. "You accept a certain short-term impact on native fauna in exchange for a long-term impact on the biodiversity."
The windmills at Altamont Pass near Livermore, Calif., kill between 40 and 60 golden eagles a year, Donlan points out, a toll that society can apparently live with. "They're killing golden eagles for wind. They certainly can kill golden eagles for endangered, listed species."
But for Jon Jarvis, the National Park Service's Pacific Region director, the solution was not so clear. When the Park Service announced its plans to kill the Anacapa Island rats, it got sued. Two men paddled out to the island and scattered pellets rich in Vitamin K, an antidote to the poison, to save the rats. When the Park Service sought to remove feral pigs from the Channel Islands, it was sued again.
"If we had that much bad press over rats, what are we going to have over eagles?" Jarvis wondered. "Clearly the last thing I wanted to do was fire up the animal-rights folks over something as charismatic as an eagle."
He conferred with representatives from the U.S. Fish and Wildlife Service and the California Department of Fish and Game, and it didn't take long for them to decide that killing golden eagles was not something they wanted to do. "We told the team that, at least at that moment, we had not exhausted heroic efforts to capture the goldens," Jarvis says. Recently, they rounded up the last pair.
Now, the pigs are gone, and bald eagles have been reintroduced and are nesting. The foxes are recovering. But for Donlan, who says money for endangered species is increasingly hard to come by, the happy ending is not unblemished. Heroic efforts like this are expensive, he notes. "A lot of conservation dollars were wasted by flying around in helicopters trying to capture golden eagles."