Santa Cruz Island FOX

(Urocyon littoralis santacruzae)

Surveys conducted from the 1970s through the early 1990s indicated the island foxes on Santa Cruz Island were doing well. However, starting in 1994 researchers noted a decline in capture success and the concurrent death of animals equipped with telemetry collars. The researchers concluded that the primary cause of death of the foxes was predation by golden eagles. Puncture wounds found in the skulls of dead foxes, as well as the presence of golden eagle feathers at the carcasses helped confirm the cause of death. Foxes completely disappeared from one long-term study area on Santa Cruz Island, and were severely reduced in another area. In 1999, an estimated 133 foxes remained on Santa Cruz Island. Golden eagles have not historically nested on the Channel Islands, but were observed as occasional visitors. It is surmised that golden eagles have more recently been attracted to the northern Channel Islands by the availability of feral pigs and sheep as a food source. It has been further suggested that the disappearance of bald eagles from the Channel Islands during the 1950s may have removed any deterrent to golden eagles that may have previously existed. As bald eagles and golden eagles do not typically overlap in their breeding areas, and both species are very territorial, the historic presence of bald eagles likely inhibited occupation of the Channel Islands by golden eagles.

To help mitigate the problem of golden eagle predation on fox populations on the northern Channel Islands, the National Park Service enlisted the services of the Santa Cruz Predatory Bird Research Group to capture and relocate eagles from the island. By April 2000, a total of 13 golden eagles had been removed from the island and translocated to other areas in California. Thus far none of the eagles have returned to the island. It is estimated that 5 more eagles are residing on Santa Cruz and Santa Rosa Islands. Current efforts by the Institute and the National Park Service involve determining the demographics of the foxes remaining on Santa Cruz Island, telemetry tracking a sample of foxes to further examine mortality factors, and maintaining a captive breeding facility on the island.