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Wild Pig Hunt Aims to Save California Island Foxes

Brian Handwerk
National Geographic Channel
for National Geographic News
March 16, 2005

On TV: Catch Explorer: Hogzilla on the National Geographic Channel (U.S.) Sunday, March 20, at 8 p.m. ET/9 p.m. PT.

The Channel Islands off the California coast are home to 145 species of plants and animals found nowhere else in the world. On Santa Cruz island, non-native feral pigs may be pushing the island's unique and endangered foxes to the brink of extinction. Now the island's managers are pushing back.

The nonprofit Nature Conservancy owns 76 percent of Santa Cruz Island. The National Park Service owns the rest. Together the agencies have crafted an island management plan that calls for an end to the pigs' tenure in paradise.

"The pigs have to go or ten species will likely go extinct, including the Santa Cruz island fox," said Julie Benson, a Nature Conservancy spokesperson. "This is a decision we had to make to preserve the biodiversity of the native species on the island."

A New Zealand-based company will begin hunting operations later this month. The company will aim to eradicate the island pig population over the next two to three years. Hunters will use a combination of traps, dogs, and helicopters to root the animals from the island's rugged terrain—one-third of which is inaccessible by road.

"We've done a lot of research to decide the most humane method to correct this situation," said Yvonne Menard, a public information officer with Channel Islands National Park. "Feral pigs are so prolific. In less than a year they can bear two litters."

She added that control of populations, as opposed to completed eradication "is really not an option" because the numbers mushroom so quickly.

Golden vs. Bald Eagles

Feral pigs churn up soil and uproot native plant species, denuding landscapes and promoting weed growth. The pigs also attract golden eagles, which prey on the charismatic island fox (Urocyon littoralis), a species found nowhere else in the world.

"Pigs exist all over the world, and feral pigs are the same species as domestic pigs (Sus scrofa)," Benson, the Nature Conservancy spokesperson, explained. "But it takes thousands of years for a subspecies to evolve. The island fox has been out there for 18,000 years."

The fox shows its evolutionary age by exhibiting dwarfism. The trait is found in isolated island mammal populations. Large island mammals become smaller through the generations as they adapt, through genetic selection, to the limited resources of their environment. (The reverse is true for small island mammals.)

The Santa Cruz island fox weighs 5 pounds (2.25 kilograms), one-third the mass of its evolutionary ancestor, the mainland gray fox.

Despite their long tenure, island fox populations have crashed to dangerous levels in recent years. They landed on the U.S. endangered species list in March 2004. Many scientists pin the problem squarely on feral hogs.

Prolific piglet production means a steady food source the golden eagle. The raptors enjoy a year-round diet of piglets, but also prey on foxes.

The island was once inhabited by bald eagles that fed on fish and carrion but not foxes. The presence of bald eagles likely prevented golden eagles from establishing themselves.

"The fox evolved for thousands of years when they had no aerial predator," Menard, the Channel Islands National Park staffer, said.

But bald eagles disappeared from the islands during the 1960s. The Park Service and Nature Conservancy place the blame on the pesticide DDT, which people dumped off the southern California coast.

In succeeding decades, protection programs have boosted golden eagle populations on the mainland. The raptors have now colonized Santa Cruz because of the piglet food source, according to Nature Conservancy and Park Service staff.

Fox Decline

The eagles' arrival precipitated a drastic decline in fox populations. In 1993 there were about 1,500 foxes on Santa Cruz. Eight years later the number had fallen below a hundred.

An ongoing bald eagle reintroduction program on the island, along with the elimination of feral pigs, is expected to prod the golden eagles to seek alternative nesting grounds.

Golden eagles are also being relocated to the mainland, an option not available for wild pigs, which the state designates as pests.

The concerted actions may come none too soon for island foxes, whose numbers have declined to the point where captive breeding is necessary.

To date, about two dozen captive-reared foxes have been successfully reintroduced to the wild.

"Massacre" Protested

Scarlet Newton is a spokesperson for the Channel Islands Animal Protection Association (CHIAPA), based in Santa Barbara, California. She believes the Santa Cruz's wild pigs have been sentenced to death under false pretenses. She said that she hopes to stop what she terms a "massacre."

CHIAPA maintains that the pigs' ground-churning habits constitute a restorative ecological benefit to Santa Cruz. The group also contends that pigs and foxes coexisted on the island for several centuries before the National Park Service began managing the island.

While entreaties to stop the pig hunt have thus far met with little response, CHIAPA said it is not giving up on its efforts to save the pigs.

"We're working from every possible angle," Newton said. "We have people looking at the situation from a legal angle. We're begging federal elected officials to please halt this project, and we're mustering public outcry to hopefully encourage those elected officials to step up to the plate."

For other non-native Channel Islands animals, such efforts come too late. In the 1980s the Nature Conservancy eliminated feral sheep from the island. A decade ago pigs were removed from Santa Rosa island. Meanwhile, other islands have been rid of non-native burros, rabbits, and rats.

Similar efforts have been carried out elsewhere in world, including the Pacific's Galapagos Islands.

Menard, the Channel Islands National Park staffer, said, "It's all been done to remove introduced species that are disrupting the natural balance of the island ecosystem."

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Photo: Bald eagle
Drawn to California's Channel Islands by non-native feral pigs, golden eagles have also preyed on the islands' unique and endangered foxes. Wildlife managers hope to lure bald eagles (pictured above) back to the islands to displace their fox-eating competitors.

Photograph by Mike Lockart, courtesy U.S. Fish & Wildlife Service
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