An Ecosystem Out of Balance on the Northern Islands - In the mid-1990s biologists on the northern islands of San Miguel, Santa Rosa and Santa Cruz began to notice a decline in island fox populations. By 2000, the northern populations were crashing toward extinction:
 San Miguel Island fox - 1994 (est. 450 foxes); 2000 (only 15 individuals remained)
 Santa Rosa Island fox - 1994 (est. 1,780 foxes); 2000 (only 15 individuals remained)
 Santa Cruz Island fox - 1994 (est. 1,465); 2002 (~62 individuals remained) bald eagle on Santa Cruz Island; photo: Peter Sharpe
This rapid population decline was due to an imbalance in the ecosystem. The island fox is the largest mammal native to the islands; it is the top terrestrial predator. It did not know how to protect itself when a new predator came to the northern islands.
Historically, bald eagles also lived on the northern islands and on Santa Catalina Island. This large bird of prey specializes in eating fish and sea birds and did not prey on the island fox. As a territorial bird, it kept other eagles from nesting on the islands.
After WWII the introduction of DDT into local watersheds and the marine environment, caused the extinction of the bald eagle on the Channel Islands. DDT is a chemical insecticide that caused the eagles to lay eggs with thin shells, which crushed under the incubating parent. Large scale ranching on the islands introduced plant-eating animals: goats, sheep, pigs, as well as deer and elk for hunting. These animals heavily impacted native plants that the island fox depended on. Ranching had limited success on the islands and the domestic animals became feral or wild.
The young pigs, goats and deer, were all potential food sources for another large bird of prey.
After DDT was banned in the 1970s and ecosystems began to recover, golden eagles moved out to the northern Channel Islands to prey on the introduced animals and eventually, the island fox.
From 1994-2000, golden eagle predation on island foxes was extreme. The golden eagle was eating the island fox into extinction.