Tuesday, July 5, 2011

The Fox-Eagle Connection

Island foxes, found only on California’s Channel Islands are among the rarest foxes remaining on earth. At less than 20 inches long and only about six inches tall, they are significantly smaller than most foxes, and have developed and evolved in an almost completely geographically isolated island environment. Each of the Channel Islands plays host to a slightly different species of island fox, and populations of many had dwindled to less than 20 animals by the late 1990s.
Island Fox
So what was the cause of this sharp decline? Surprisingly, human population growth and loss of habitat are not completely to blame in this situation, as the majority of the Channel Islands are protected land. Rather, biologists point to a shift in eagle populations. Bald eagles were once native to the Channel Islands, but in the 1960s their populations were decimated due to use of the pesticide DDT. With the bald eagle gone, smaller golden eagles began nesting on the Channel Islands; and whereas the bald eagles eat fish, golden eagles prey upon mammals.
Golden Eagle
The golden eagle presence seemed to have little effect on island fox populations for nearly 30 years. Then in the early 1990s the National Park Service exterminated the nonnative feral pigs that had been introduced to the islands, eliminating the golden eagle’s primary food source. Due to their isolation and lack of any natural predators, the island fox was not equipped to being preyed upon, and because of this were nearly driven to extinction.

Conservationists are taking a multi-pronged approach to protecting the island fox. They are making attempts to capture and relocate golden eagles and other nonnative species to the mainland, and are no longer allowing visitors to bring pets to national parks on the islands, as island foxes are susceptible to diseases from domestic dogs. Finally, attempts are being made to reintroduce bald eagles to the Channel Islands, as a healthy bald eagle population would prevent the return of golden eagles. These steps combined with captive breeding programs will hopefully allow this rare species to continue on.
Island Foxes in Captivity

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