The story of the Island Fox is fascinating, with an interacting and ever-shifting cast of key characters. There’s also a hidden lesson about why many attempts to restore nature fail and what we can do about it.
The Island Fox is a colorful endemic found on only six small islands – the Channel Islands – 20 miles off the coast of California. A descendant of the gray fox, the Island Fox has changed dramatically since becoming island bound thousands of years ago (the exact timing of isolation is still a mystery). Not only has insular dwarfism made it nearly half the size of its ancestor (4.5 vs 8.5 pounds), the Island Fox has also become a daytime, rather than nighttime, hunter. Being small and diurnal were likely advantageous adaptations to island living, at least until humans got involved.
In the mid 1800’s, European settlers made major changes to the Channel Islands by introducing pigs, which quickly became feral. Pigs have little direct effect on Island Foxes, but the soil-shifting sow snouts have destroyed much of the Islands’ unique plants and sacred cultural resources. Fourteen endemic plants, considered a treasure of our national heritage, are now on the endangered species list, and conservationists want to remove the pigs to restore the plants. Indeed, removing non-native species is a pillar of modern conservation.
But, not so fast! Although the pigs have little direct effect on the Island Fox, a secondary change on the islands has intertwined the story of the fox, the pigs, and the plants.
One hundred years after the pig introduction, Rachel Carson’s voice was ringing loud in the silence of spring. The mass production and application of DDT, that Carson made famous for its devastating impacts on birds, was in full swing. The impacts of DDT were especially deadly for Bald Eagles that ingested mega doses of pesticides that accumulated in the fish they preyed on. Despite their isolation from the mainland, Bald Eagles of the Channel Islands were not spared from the pesticide’s devastating effects. By the mid 1900's, Bald Eagles no longer nested on the Islands’ rocky cliffs or Torrey Pines.
Without Bald Eagles to defend the cliffs, smaller and less competitive Golden Eagles quickly colonized the Islands. An eagle swap seems like a minor change to an ecosystem, but a small difference between the eagles would soon haunt the Island Fox.
Bald Eagles get their food mainly from the ocean, but Golden Eagles feed on land. Not only does this make Golden Eagles less susceptible to DDT, but the dietary difference between the eagles changed the hierarchy on the Islands. Prior to the arrival of the Golden Eagle, the Island Fox lived a luxurious life hunting under the warm California sun without predators. But with the arrival of Golden Eagles, the bite-sized Island Fox became the hunted.
So why not just remove the pigs to save the plants? Because, without pigs, the Island Fox becomes the main dish on the Golden Eagle’s menu. Even with pigs to prey on, Golden Eagle predation nearly caused Island Fox extinction in the late 1900's. If conservationists had removed the pigs, the Island Fox would surely be gone forever.
Luckily, conservationists identified this conundrum and set a carefully orchestrated plan into action to restore the plants without losing the fox. First they captured and relocated the Islands’ population of Golden Eagles. They then reintroduced Bald Eagles to keep the Golden Eagles from returning. With the birds back in balance, they removed the pigs. And finally, after a little captive romance, they started the recovery of the Island Fox. It’s an amazing conservation collaboration and success story captured in this great video by the National Park Service. It’s also a case study that helps explain a plethora of seemingly disparate conservation failures.
There’s a common thread among many conservation failures and the story of the pig, eagles, and Island Fox. Often, plants and animals become threatened by an initial disturbance such as the introduction of a non-native species, habitat destruction, pollution, or overharvesting. Our natural reaction as conservationists is to simply remove that initial disturbance to recover the ecosystem. We see it all around us with dam removals, pesticide bans, or harvest reductions.
But conservation is rarely so simple. The recovery of a population is often complicated by a secondary change to an ecosystem, like the loss of an important player, such as the Bald Eagle. Once the secondary change occurs, removing the initial disturbance might have little effect, or worse yet, cause more harm, like the extinction of the Island Fox. It’s a quandary referred to as the Humpty-Dumpty effect: despite having all the pieces of a shattered ecosystem, the ecosystem might be difficult to piece together again.
In our recent paper, we show that this Humpty-Dumpty effect is rarely acknowledged in published restoration studies, but might be important in explaining some conservation failures. The Humpty-Dumpty effect also teaches us some valuable conservation lessons. For example, we need funding for natural history research to ensure we use limited conservation resources efficiently, and don’t cause more harm than good. Had ecologists not documented the detailed natural history of the Channel Islands ecosystem, from the origin of the island fox to the importance of an eagle swap, the Island Fox would surely be gone forever.
Natural history research is often supported by state and federal agencies such as the National Park Service, U.S. Fish and Wildlife Service, or your state fish and wildlife management agency. Keep that in mind when you vote, and always remind your governmental representatives how much you appreciate these agencies. Without funding for natural history research, we won’t learn the next set of valuable lessons that foxes, eagles, and the rest of nature are trying to teach us.
And that’s just one lesson. There are more lessons to learn when we take an eco-evolutionary perspective on Humpty-Dumpty conservation, which is the subject of my next post in this series. You can also learn more about the Humpty-Dumpty effect, interesting case studies, and its importance in conservation in our paper “An Eco-evolutionary Perspective on the Humpty-Dumpty Effect and Community Restoration”.
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