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"Hack" towers house juvenile bald eagles until they are ready to fly © Jeffery Wilcox |
Though only the size of a small house cat, the island fox was Santa Cruz Island’s top predator for thousands of years—until golden eagles from the mainland began nesting on the island in the 1990s. Attracted by the abundance of feral pigs, the predatory birds also preyed upon the island fox. Within a few years of their arrival, golden eagles had hunted the island fox to near extinction.
Without intervention, the island fox will perish, and one-of-a-kind plant species will disappear. The National Park Service, The Nature Conservancy and the U.S. Fish and Wildlife Service are pooling their resources to save the island fox and help preserve the unique, biological richness of Santa Cruz Island .
Their intensive, science-based restoration program includes five main components:
- Breeding island foxes in captivity
and monitoring the wild population;
- Relocating golden eagles;
- Reintroducing bald eagles;
- Eradicating feral pigs; and
- Controlling invasive weeds.
Island Fox Recovery
In 2002 the National Park Service and The Nature Conservancy initiated a captive breeding program on Santa Cruz Island to help restore the island fox population to its historical levels. Using telemetry, biologists identified mating pairs, then carefully captured and transferred the foxes to large, airy pens set in the natural environment. In three seasons the foxes have given birth to more than 30 pups.
Biologists are also monitoring foxes in the wild, where fewer than 100 remain. More than 60 wild foxes have been fitted with radio collars, enabling researchers to study their movements and keep close tabs on the population. Should too many fall prey to golden eagles or other threats, biologists will transfer the wild foxes to the captive breeding facility until the threat can be mitigated.
In compliance with the Endangered Species Act, the U.S. Fish and Wildlife Service (USFWS) has appointed a technical committee to advise the island fox recovery effort on four Channel Islands—Santa Cruz, Santa Rosa, San Miguel and Santa Catalina. The committee includes scientists from USFWS, The Nature Conservancy and the National Park Service, as well as renowned fox experts from academic institutions throughout the country.
Removing Golden Eagles
In 1999 the National Park Service, The Nature Conservancy and the U.S. Fish and Wildlife Service began removing golden eagles from the island. To date, more than 30 golden eagles have been captured and relocated to the eastern Sierra Nevada Mountains. None of the birds has returned.
Golden eagles will continue to be trapped and relocated from Santa Cruz Island until they no longer threaten the island fox population. Fewer than a dozen golden eagles remain on the island. Reintroducing Bald Eagles
The National Park Service and the Institute for Wildlife Studies (IWS) began reintroducing bald eagles to Santa Cruz Island in 2002. Historically native birds, bald eagles disappeared from the Channel Islands in the late 1950s following DDT contamination of their ocean-based food supply.
Every summer through 2006, IWS will transport a dozen eaglets from Alaska or the San Francisco Zoo to roomy, screened hack towers on Santa Cruz Island. Perched high above the sea, the bald eagle chicks typically remain in the towers for a month before the tower gates are lifted and the eagles take their first flight.
Scientists believe the territorial bald eagles—which eat fish and carrion, not foxes—may keep golden eagles from recolonizing Santa Cruz Island once they reach maturity in five years. The Montrose Settlements Restoration Program, established to restore resources injured by DDT dumping in southern California, is financing the entire operation.
Eliminating Feral Pigs
The future of the island fox and nine threatened plants on Santa Cruz Island will never be secure until feral pigs are removed. Not only do feral pigs attract golden eagles, they root up entire hillsides and disturb ancient Chumash archaeological sites.
Soon, The Nature Conservancy and the National Park Service will begin eliminating the feral pigs through a professional hunting firm. Carriers of disease, the pigs cannot be returned to the mainland, nor is there effective contraception for the fast-breeding animals.
Santa Cruz Island has been divided into five fenced sections to facilitate the eradication program. Each fenced section will be monitored for two years after the feral pigs are removed. Scientists are confident the eradication program will give Santa Cruz Island's endangered species a fighting chance—just as the elimination of feral sheep in the 1980s gave the island's nearly barren landscapes the chance to recover. Controlling Invasive Weeds
Because feral sheep and pigs have grazed and disturbed so much of the land over the past 150 years, fennel now covers some five percent of Santa Cruz Island’s surface. An aggressive weed that came to the island in the 19th century, probably with domestic livestock, fennel grows in tall, woody thickets that block out native plants.
With help from researchers from the University of California and California State University systems, The Nature Conservancy is removing fennel to allow the island’s natural plant communities to take root once again. Carefully controlled prescribed fires and judicious application of herbicide have helped to reclaim nearly 500 acres. When pigs are removed from the island and are no longer digging up the soil, researchers will develop a more comprehensive strategy for reducing invasive weeds on a larger scale.
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