Writer: Norman Martin
LAS CRUCES - A New Mexico State University researcher reports this week in the journal Science that conservation of endangered species facing extinction may require drastic measures that are emotionally, politically and legally challenging.
A prime example is found off of California's idyllic coast on the Channel Islands among a competing population of endangered island foxes, protected golden eagles and some feral pigs. "Basically it comes down to this; if the fox is to be saved, the eagles are going to have to go," said Gary Roemer, an NMSU wildlife ecologist who co-authored the study with scientists at the University of California-Davis and France's Universite Paris-Sud.
Today, the tiny island fox lives on six of eight Channel Islands located about 30 miles off the Southern California coast. Populations of four island fox subspecies have plummeted on Santa Catalina, San Miguel, Santa Cruz and Santa Rosa islands, dropping from approximately 4,600 in 1994 to fewer than 400 in 2003.
One reason for the decline has been the golden eagle's inclination to feast on the foxes, which are the size of a house cat and weigh only about 5 pounds. Golden eagles, which have been protected in the United States since 1962, can have wing spans of more than 7 feet and weigh 8 to 12 pounds.
Starting in 1999, in an effort to save the endangered foxes, wildlife researchers with the Santa Cruz Predatory Bird Research Group began relocating some 31 of the golden eagles. However, the 7 to 10 remaining eagles couldn't be caught and blocked the recovery of the foxes.
The next step in an effort to save the foxes lay in reducing the feral pig population, which were introduced on the islands in the 1850s. But Roemer and his two co-authors found an unexpected result. A demographic model projecting future fox populations developed by co-author Franck Courchamp in France revealed that purging the pigs led to a decline and eventual extinction of the foxes unless the eagle numbers were also controlled.
"It's counterintuitive," Roemer said. "But it appears that eagles will increase pressure on the foxes if they can't get pigs. So, the recovery of the foxes is directly proportional to the intensity of eagle removal."
It's a paradox, Roemer admitted. Protection of the island fox, an endangered species, depends on the complete removal of a small population of golden eagles, a protected species. But any removal of these birds of prey has significant legal challenges.
So far, state and federal wildlife authorities are still mulling over this biodiversity dilemma. Completely removing the golden eagles, including using lethal means, would face sharp legal hurdles. Both the U.S. Migratory Bird Treaty Act and the U.S. Bald and Golden Eagle Protection Act prevent taking of golden eagles, except under special circumstances.
Four subspecies of island fox likely will be listed as endangered under a legal agreement hammered out this month with two nonprofit wildlife groups that petitioned the U.S. Fish and Wildlife Service to win added protection for the rare predators. The agreement also calls for the agency to map out and protect critical habitat for the foxes. Fish and Wildlife is expected to list the four subspecies as endangered by March 1.
© 2013 New Mexico State University Board of Regents
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