SANTA CRUZ ISLAND, Calif. — Norm Macdonald rises each morning with the sun, grabs his .223-caliber rifle and slips into the passenger seat of a tiny, doorless helicopter for another day of shooting pigs.

As the chopper skims over rugged terrain, Macdonald scans dozens of simple fence traps he’s set up for the thousands of wild swine that have overrun this Southern California island.

When there are pigs in the traps — and there always are — Macdonald leans out and pumps two bullets into each animal: one for the heart and one for the head.

Each pig’s death brings conservationists one step closer to their goal of saving the tiny Santa Cruz fox, an endangered species found only on this 96-square-mile island off Santa Barbara. Experts believe it’s the best way to mend the island’s delicate ecological web, which was torn when, as early as the 1850s, domesticated pigs escaped from now-abandoned ranches.

The killings have angered animal rights groups and forced the National Park Service and The Nature Conservancy, which co-own the island, to answer why groups dedicated to protecting animals are instead paying $5 million to kill them.

“It’s not just about killing pigs, it’s about saving a native species. There’s nothing unique about these pigs,” says Lotus Vermeer, The Nature Conservancy’s project director for Santa Cruz Island. “What we’re choosing to do here is save biodiversity.”

Macdonald and his eight-man hunting team from the New Zealand-based Prohunt Inc. have started fast — killing in two weeks 800 of the island’s estimated 3,000 pigs. They expect the entire process to take more than two years, eventually incorporating trained dogs, infrared sensing devices and radio trackers as the most elusive pigs try to outfox the hunters.

More than 150 years of ecological chaos brought Macdonald here — and if biologists are right, the island’s future depends on his success.

In 1853, the first ranch pigs broke into the wild and, within a few years, their population swelled to hundreds. Voracious scavengers, the pigs dug into hillsides as they foraged for bulbs and grubs and rototilled for acorns under majestic oaks, tearing up the roots.

That triggered erosion, destroyed Chumash Indian archaeological sites up to 8,000 years old and encouraged the growth of nonnative plants that choked out scrubby oaks and grasses. Fennel, an invasive species, now grows so prolifically that on a hot day the air carries the plant’s licorice scent.

The National Park Service has in the past eradicated nonnative sheep, rats, rabbits and mules on other of the Channel Islands.

In the early 1990s, the fox began to disappear from Santa Cruz Island at an alarming rate.

Biologists concluded that golden eagles, attracted by the easy prey of piglets, had colonized the island — and were also feasting on fox. For years, the dominant and fish-eating bald eagles had kept the golden eagles away, but they were wiped out by DDT dumped off the coast beginning in 1947.

The fox population plummeted more than 90 percent, from more than 1,000 to fewer than 100 animals today. Last year, the federal government listed the fox as an endangered species.

The public park service and the private Nature Conservancy believe that only aggressive human intervention will save the fox.

Eradicating the pigs, their logic goes, will force golden eagles to search elsewhere for food, letting the fragile fox population rebound. To help that process along, biologists have relocated 29 golden eagles to the Sierra Nevada and also introduced 34 bald eagle chicks and bred 34 fox pups on the island.

Russell Galipeau, superintendent of the Channel Islands National Park, acknowledges that killing one species to save another puts his agency in an awkward position. The pig eradication, he says, fits his agency’s mission of restoring the island to its natural state while saving native species and protecting archaeological sites.

Federal and state law prohibits relocating the pigs, which may have pseudorabies and cholera, to the mainland. Sterilization and contraception aren’t practical because the plan would fail if biologists miss only a few pigs — the fast-breeding pigs can rebound from a 70 percent population reduction in just one year, according to Galipeau.

Critics have argued that, after so long on the island, the pigs belong as much as the foxes.