Christina Boser sits at the edge of a eucalyptus grove cradling an impossible creature. It’s smaller and slimmer than your average housecat, with tiny paws and a pointed snout. Its coat is subtly speckled black and white, like TV static, turning rusty around the animal’s ears and belly and fluffy tail.
Grasping it by the neck, Boser pulls a blindfold over the creature’s snout and eyes, then runs a comb along its back and sides. There, a flea. Another swipe and two more fleas. She grabs a syringe, feels around her patient’s rear leg for a good muscle, and injects a distemper vaccine. Then she flips the animal over, feels around, and injects again, this time for rabies.
Boser undoes the blindfold’s velcro and looks the creature in its eyes. “Hi,” she says, rubbing its leg with her thumb. It doesn’t flinch, and it doesn’t grumble. When Boser loosens her grip, the critter rockets away, stopping 30 feet down a dirt road to look back before disappearing around the grove.
So goes the island fox, an achingly beautiful creature that lives here on Santa Cruz Island (and a handful of other Channel Islands), off the coast of Southern California. Just 12 years ago, fewer than 100 foxes remained on Santa Cruz, driven toward extinction by voracious golden eagles who’d incidentally pick off the foxes while hunting the island’s feral pigs. Now, thanks to Boser and her colleagues at the Nature Conservancy, the island fox numbers over 2,000. On August 11, the Environmental Protection Agency pulled the island fox from the Endangered Species List—the fastest turnaround ever for an endangered mammal.
Conservationists were only able to save the fox by turning its home into a war zone, complete with snipers and helicopters. This, after all, is the anthropocene. Humans have mucked up nearly every ecosystem they’ve touched—and people like Boser desperately want to put those ecosystems back together again. But that restoration comes at enormous monetary and biological cost.
Resetting something as wildly complex as an ecosystem is an intricate balance of subjective ethics and scientific calculations. As humanity inflicts more and more harm on the ecosystems of Earth, conservationists have developed increasingly sophisticated ways of saving imperiled species. Santa Cruz Island is just one battleground in a larger war, as humans grapple with the threat of invaders—including themselves.
How to Shrink, Nearly Lose, and Save a Fox
You’d struggle to dream up a more charismatic bit of megafauna than the island fox. It’s inquisitive, yet skittish. (Standard island fox operating procedure: Run away from you, stop, look back, run some more, look back.) In its isolation on Santa Cruz Island, it has shrunk to less than half the size of its mainland ancestor, the gray fox. Trapped on an isle with limited food and water, foxes with smaller, more resource-efficient bodies may have had a selective advantage. And without any predators on the island, the fox’s small size wasn’t a liability.
That is, until humans showed up. In the middle of the 19th century, ranchers arrived on Santa Cruz Island, bringing pigs with them. Over time, those pigs turned feral, tearing up the island as they rooted for food. And their piglets attracted golden eagles—for whom the diminutive island fox was equally delectable.
You’d struggle to dream up a less charismatic bit of megafauna than a feral pig. It’s hungry, breeds rapidly, and ravages ecosystems in its search for food. So in the early 2000s, conservationists weighed the worth of the island fox, on the edge of the destruction, against the feral pig, pushing the fox closer to that edge. Killing off common pigs to save an entire unique species of fox was a simple value calculation. You could ship the golden eagles off the island no problem, but with the pigs still here, the birds would keep on coming back. The swine had to go.
But the proposed campaign didn’t go over well with everyone. A previous cull on the island to remove a population of feral sheep left “lambs starving by their dead mothers” and “wounded sheep trying to crawl to safety,” as UC Santa Barbara ethicist Jo-Ann Shelton wrote at the time.
Shelton didn’t actually object to the cull itself. The pigs didn’t belong here, and the pigs had to leave. “It wasn’t the fact that they were trying to eliminate the animals,” she says. “It was that they weren’t using humane methods.”
The Nature Conservancy considered nonlethal methods like giving contraceptives to the swine, but that would just get you an island of hell-raising, infertile pigs—assuming you could somehow get the meds to the entire population and the contraceptives were 100 percent effective. “The golden eagles that occasionally show up at the island would have more food available, and we’d probably have to conduct additional golden eagle transports to the mainland,” says Boser.
The Conservancy decided to go with bullets.
Starting in March of 2005, a New Zealand outfit called Prohunt waged war against the swine. This was an extremely disciplined crew. “They had a thing when you were dispatching a pig: If you didn’t think you could get all the pigs in the group, do not even start,” says Boser. “Because if you let one educated pig go, that’s going to cause you problems.”
The hunters divided the island into five zones. They would exterminate the pigs in a given zone and move to the next, guaranteeing that the swine couldn’t just flee to another part of the island. Pig by pig, zone by zone, they’d trap the pigs or track them down with trained dogs. But mostly they flew around in a helicopter, methodically sniping pigs from the air. The hunters dispatched over 5,000 swine.
Some pigs, though, they first captured, sterilized, tagged, and released. “Pigs like making friends,” says Boser. “They’re social animals. So if you sterilize one, you take it away from its group, let it go, it’s going to find new friends.” The hunters would then track the Judas pig to its new cronies and dispatch them all.
Fourteen months and $5 million later, the pigs were gone. But Santa Cruz Island’s troubles weren’t over.
Fragile Rocks in the Sea
An island is a paradox. Its isolation means that it’s easy for an invasive species to slaughter natives naive to new threats. But closed systems are also relatively easy for conservationists to restore: Those invaders have nowhere to flee. “Once you’ve eradicated pigs or goats or rats from an island, it takes a large effort for those animals to recolonize,” says David Steen, an ecologist at Auburn University. “So islands are the best and the worst as far as ecological restoration is concerned.”
But where to attack? And how to attack? Conservation used to be a matter of trial and error, of figuring out what method works for what environment and for what species. But conservation is now a calculation. And at stake are not only time and a whole lot of money, but lives.
Before building a kill list, scientists have to quantify the harm a given invasive species is causing. This can be economic—say, an insect making a mess of agriculture. Or it can be ecological: What native species is the invader imperiling, and what would happen to the ecosystem if the natives disappeared? Beyond that, conservationists must determine if it’s even feasible to eradicate a given species.
As the calculus of conservation grows more sophisticated, so too do the methods of eradication. Consider the unmitigated catastrophe that was the eradication of felines from Marion Island, far off the coast of South Africa, in the second half of the 20th century. Eradicators tried releasing a lethal virus, trapping the cats, shooting them, hunting them with dogs, and deploying poisons. It took nearly two decades. Compare that to the trapping of cats on San Nicolas Island, south of Santa Cruz Island, in 2009 and 2010. Conservationists trapped the felines and shipped them to a rehab center on the mainland, restoring the ecosystem in a fraction of the time with none of the cruelty.
In the future, ecologists might cull an invasive species not with bullets but with DNA—with what’s known as a gene drive. “You can introduce an edited gene that, for example, causes all the females to have only male offspring, and eventually the population dies,” says Daniel Simberloff, an ecologist at the University of Tennessee, Knoxville. With a large mainland population, the gene might not be able to spread far enough. “But on islands, it might work,” Simberloff says. “And so there’s a lot of interest in this now.”
Eradication methods are only getting better, thanks to data, data, and more data. Scientists have started to use algorithms and satellite images to pinpoint hot spots of biodiversity, the places where conservationists could save the most species for their time and money. The group Island Conservation uses a public database of threatened islands to determine which habitats need urgent attention, based on factors like the number of threatened species and the feasibility of restoration. Conservationists were able to ship all the cats off San Nicolas Island so quickly in part because they used camera traps to determine well-trafficked areas before deploying their traps. And today, camera traps can even automatically recognize the species they’ve detected.
Sugar Balls of Death
A white helicopter, basket dangling below, pops up over a ridge and passes low overhead. Its pilot leans out of an open door, getting a better look at his target on a dirt airstrip: a giant metal hopper. Slowly he lowers the basket, which two workers in coveralls and bandana facemasks grab and guide to the container. One pulls a lever, and thousands of glistening beads of poison pour into the basket. The helo zooms off again, bearing its deadly cargo toward its target: the Argentine ant.
Threats to an island ecosystem aren’t always as conspicuous as the feral pig. It’s easy to understand conservationists’ choice to dispatch the swine in order to save a unique (and uniquely charming) fox. But when it comes to actually saving the island’s ecosystem, the organization’s battle against the Argentine ant may be even more important.
On Santa Cruz Island, invasive Argentine ants don’t just kill native ants. “They steal nectar and they guard that nectar, and they don’t allow the pollinators to come in,” Boser says. That means fending off both bees and the native ants that actively pollinate flowers, setting off a cascade of shocks. These insects are largely unnoticed, yet they’re hugely important. So while the Argentine ant may be tiny, left unchecked it could rival the pigs in ecological destruction. The Conservancy’s calculation here was simple—take out the ant now or pay a heavier price down the road as native ants perish and the flora struggles to reproduce.
The tricky thing about the Argentine ant is it doesn’t stray far from its nest to forage, so you can’t just place bait sporadically and expect results. Boser’s solution, then, wasn’t a big bomb of toxin here and there, but a cluster bomb dropped from the air: little balls soaked in a mixture of sugar, water, and just 0.0006 percent poison. Boser calls them “sugar balls of death.”
Each Argentine ant colony can support dozens of queens, which sound an alarm to stop feeding if they detect something wrong with the food supply—for instance, if it’s poisoned. Hence the super-low concentration of toxin in the sugar balls of death. The Argentine ant workers suck up the liquid and feed it to the colony, including the queens. The queens don’t realize something is amiss until it’s too late. Everyone eats, and everyone dies.
Of course, as with any eradication plan, the sugar balls of death have drawbacks. Problematically, they don’t care what they kill: Native ants, too, will gobble up the liquid and perish. But the Argentine ants were only able to conquer 2 percent of Santa Cruz Island. Wipe out the ants in that 2 percent, the Conservancy reckons, and the native ants will wander back in and restore the natural order—while the Argentine variety joins the feral pigs and feral sheep as past menaces, not present.
Foxes on Top of the World
Santa Cruz Island is no place to miss a sunset. Boser is powering up a dusty mountain road in a Nissan Xterra, bounding up bumps, down into gullies and rain-carved divots. Branches slap the doors and dust comes in through open windows.
She apexes onto a ridge and piles out, clambering up a hill. The sunlight paints the mountain grasses gold, throwing long shadows. In the distance, fog is pouring into the ocean. To the left, 100 feet away, a pair of foxes stare mutely at the newcomers. They take off, stop, look back, run away a bit more, stop, look back, and run away more. As the island fox is wont to do.
Boser makes smooching noises to get them to come back, then bends down and ruffles the dirt. “I was just trying to be interesting,” she says. “But most of the time they don’t seem to care.”
Humans—Boser and her team in particular—are the island fox’s savior. But they have also always been its biggest threat. Ranchers brought the pigs, after all, and the pigs attracted the golden eagle. And as it turns out, humans might have brought the foxes here in the first place.
For a long while, the thinking went that the fox made its way from the mainland between 10,000 and 16,000 years ago on a raft, when sea levels were lower. Yet thus far, scientists have only found fox remains on Santa Cruz Island as old as 6,000 years, a few millennia after native peoples showed up here.
The island fox may itself be an introduced species. It just happens to be the one humans want to keep.