California island foxes recover after authorities remove golden eagles

Authorities in California successfully restored the island fox population on the Channel Islands by removing golden eagles and eradicating feral pigs.

During the 1990s, the island fox faced a rapid decline on the archipelago. On Santa Rosa Island, the population plummeted from 1,780 to just 15 individuals, while Santa Cruz Island saw numbers drop from 1,400 to 55. Researchers identified a phenomenon called pig-mediated hyperpredation as the cause of the decline.

For decades, ranchers brought pigs to the islands, where they multiplied uncontrollably. This abundance of food attracted golden eagles from the mainland. The eagles began hunting the island foxes, which lacked natural defenses against aerial predators because they had evolved in an environment without them. To save the foxes, officials organized expeditions to capture and relocate 44 golden eagles away from the archipelago.

They also launched a 5 million dollar eradication program to remove feral pigs, successfully eliminating 5,036 pigs in about 400 days. To prevent the eagles from returning, authorities introduced the American pygmy-eagle, a territorial bird that competes with the golden eagle and feeds on fish and seabirds. These actions led to one of the fastest recoveries for an endangered mammal.

Today, the fox population on Santa Cruz Island has grown to 3,086 individuals, and the population on San Miguel Island stands at 322.