San Miguel Island had 450 foxes before golden eagles cut the population to 15; conservation efforts helped rebuild it to 322 by 2024

In the late 1990s, San Miguel Island off the coast of Southern California was home to just 15 island foxes, down from an estimated 450. Three decades later, the population has recovered to roughly 322 animals. The turnaround followed an intensive conservation programme that tackled several causes of the decline at once, including the removal of golden eagles, the eradication of feral pigs that had helped sustain them, the reintroduction of bald eagles and a captive-breeding programme for the foxes. The collapse was not limited to San Miguel. On neighbouring Santa Rosa Island, the fox population fell from about 1,780 to 15, while Santa Cruz Island dropped from more than 1,400 to 55. In 2016, the U.S. Fish and Wildlife Service removed the San Miguel, Santa Rosa and Santa Cruz Island fox subspecies from the federal endangered species list, describing the recovery as the fastest successful recovery of an Endangered Species Act-listed mammal in the United States.Why golden eagles nearly wiped out the island foxThe collapse of the northern Channel Islands' foxes was linked to a major change in the islands' predator community. Bald eagles had historically occupied the islands, but their populations declined because of DDT contamination, along with hunting and egg collection. With the bald eagles largely gone, golden eagles began establishing themselves as resident breeders on the northern Channel Islands. Unlike bald eagles, golden eagles hunt terrestrial mammals and were capable of killing the much smaller island foxes. The arrival of golden eagles coincided with the beginning of the fox decline on San Miguel. National Park Service biologists tracking 15 radio-collared foxes between 1998 and 1999 believed five had been killed by golden eagles. On Santa Cruz Island, an earlier investigation identified golden eagle predation as the cause of death for 21 of 29 fox carcasses examined.The predators also had an unusually reliable food source on the islands. Feral pigs, introduced to Santa Cruz Island in the 19th century, had multiplied into thousands of animals. Their piglets provided golden eagles with a substantial prey base, helping the large raptors establish and maintain territories on the island. The presence of this non-native food source, combined with the loss of bald eagles, helped create conditions in which golden eagles could remain on the islands and prey on foxes. San Miguel and Santa Rosa each reached just 15 foxes, while Santa Cruz fell to fewer than 80. On Santa Catalina Island, a separate threat caused a similarly dramatic decline when canine distemper killed around 90% of the fox population in the late 1990s.How removing eagles and breeding foxes reversed the declineWildlife managers recognised that simply breeding more foxes would not solve the problem while golden eagles remained on the islands. Beginning in 1999, the National Park Service and its partners started capturing and relocating golden eagles from the northern Channel Islands to the mainland. Between November 1999 and July 2006, 44 golden eagles were removed from Santa Rosa and Santa Cruz islands and released in northeastern California. Monitoring found no subsequent breeding by golden eagles on the northern Channel Islands. Managers also worked to restore the ecological conditions that had existed before the golden eagle invasion. Between 2002 and 2006, the Institute for Wildlife Studies released 61 bald eagles on Santa Cruz Island. The species eventually began nesting successfully on the northern Channel Islands, restoring a predator that could compete territorially with golden eagles without posing the same threat to island foxes.The feral pig population on Santa Cruz Island was tackled at the same time. More than 5,000 pigs were removed in 2005 and 2006, eliminating the major non-native prey source that had helped support resident golden eagles. The last feral pig was removed from Santa Cruz in 2007. Foxes were also brought into captivity as an insurance policy against extinction. Captive breeding programmes were established on the affected islands, and 226 foxes were eventually released back into the wild across the recovery effort. Captive and wild foxes were also vaccinated against canine distemper. The interventions worked together rather than operating as a single solution: predator pressure was reduced, the food source supporting golden eagles was removed and the fox populations were supplemented with captive-bred animals.From 15 foxes to roughly 322 on San MiguelThe response produced a rapid increase in fox numbers. By 2011, the San Miguel population had already returned to close to 400 adult foxes, which the National Park Service considered biologically recovered. By 2015, the island was estimated to have approximately 700 foxes. The federal government formally recognised the recovery in 2016. The U.S. Fish and Wildlife Service removed the San Miguel, Santa Rosa and Santa Cruz island fox subspecies from the endangered species list, while the Santa Catalina subspecies was downlisted from endangered to threatened. The Interior Department described the three delistings as the fastest successful recovery of an ESA-listed mammal in the United States. More recent monitoring shows that San Miguel's population has settled at a considerably lower level than the peak recorded during the recovery. According to the Island Fox Status Update 2025, compiled by Friends of the Island Fox from a May 2025 working group meeting, San Miguel had 322 foxes in 2024, down from about 525 the previous year. Researchers reported that pup numbers were typical and individual health appeared good, while the island's resources were thought capable of supporting approximately 300 to 450 foxes.The change therefore does not necessarily represent a return to the crisis conditions of the late 1990s. Instead, the latest monitoring suggests the San Miguel population may be fluctuating around the level its available resources can sustain. The island's foxes remain subject to regular monitoring because a population confined to a single island can still be vulnerable to disease, changes in food availability and renewed predator pressure. The wider Channel Islands picture also shows why continued monitoring matters. Santa Cruz Island had an estimated 3,086 foxes in 2024, while the San Clemente Island fox population recorded a third consecutive year of decline. Adult survival on San Clemente fell from an estimated 89% to 69%, and only seven pups were documented in 2024. Investigations are continuing into the causes, including possible effects from disease, food resources, wildfire and vehicle strikes. San Miguel's recovery therefore was not simply a matter of releasing captive-bred foxes into the wild. It required changing the conditions that had pushed the animals towards extinction in the first place. From 15 foxes in 1999 to roughly 322 in 2024, the population now occupies an island where the golden eagle threat has been largely removed and the ecosystem has been altered to make long-term survival possible.Catch the latest World News and Live updates. Download the TOI app.