In late March, on a glacier-riven sliver of land 1,000 miles off the coast of Antarctica, a team of conservationists completed the largest rat eradication ever attempted. Over the course of four years, and at a cost of $12 million, they used helicopters to bombard South Georgia Island with almost 400 tons of poison bait. It’s the most ambitious attempt yet to turn back the rats, and the mission’s measure for success is unforgiving: if a single rat is left alive, they’ve failed.
When project leader Dr. Tony Martin first visited South Georgia 20 years ago, the impact of the rats was stark. Neighboring rat-free islands were brimming with birds and lush with plants fertilized by their droppings. South Georgia itself, however, was barren as a desert. “I thought at that time if I could ever get rid of the rats I’d die a happy man,” Martin said, at home in Cambridge after a long journey from the South Atlantic.
Before humans set foot on its shores, South Georgia was a refuge for penguins, albatrosses, and other seabirds. But then came the sealers, and they brought the rats, which devoured the birds: eating eggs, chicks, and even fully grown birds, Martin said, grabbing their necks and devouring their brains while still alive. It’s estimated that 90 percent of the island’s seabirds have been wiped out by rats.
South Georgia’s story has played out on islands around the world. A disproportionate amount of the world’s biodiversity lives on islands, where species often evolved in isolation from mammalian predators. But when rats arrived, these ecological niches became smorgasbords. Burrowing, ground-nesting, and flightless birds were eaten quickly. Baby tortoises were gnawed to death. Rats are responsible for about half of all bird and reptile extinctions on islands, according to Gregg Howald of the group Island Conservation.
“I have enormous regard for rats,” Martin said. “I get no pleasure out of killing them. But the way I look at it, and I recognize this is a very imperialistic view, is that something is going to die here whether we do something or not, and the choice therefore is not whether to kill or not, it’s whether we kill rats, which were introduced by man, or allow the rats your forebears put in place to eradicate the native population. Because I have the power, the resources, to kill rats, and hereby save species from going extinct, I choose to use that power.”
Aerial rat eradication was pioneered in the 1990s in New Zealand, where, as Elizabeth Kolbert wrote last year, defending native birds has become an issue of nationalism. They are, after all, Kiwis. Conservationists loaded poison into modified fertilizer buckets and used them to disperse bait evenly over entire islands. Some birds would succumb to the poison, but it was worth it: researchers found that if they killed every last rat, native bird populations quickly rebounded beyond pre-eradication levels. GPS changed the game, according to Keith Springer, a New Zealand conservation officer who worked on the South Georgia mission. It let them overlay islands with a close-knit grid that helicopter pilots could trace, ensuring that no spot is missed.
Other groups copied the strategy. In 2007, Ecuador began clearing the Galapagos Islands of rats, which threatened to wipe out the islands’ tortoises. The eradication program was a success: last year, for the first time in over a century, tortoises were born in the wild on Pinzon Island and survived. In the Aleutians, the US Fish and Wildlife Service killed every rat on Rat Island, where a shipwreck had deposited them in the 1780s. Puffins and cormorants quickly returned, and the island was renamed Hawadax.
At 100 miles long, South Georgia is the most ambitious island eradication effort attempted yet. The team divided the island into three sections, each separated by a glacier, and used helicopters to fly along the GPS grid they’d drawn, flinging poison nuggets from a bucket 150 feet above the ground. It’s been several years since the first two sections were poisoned, and the team has seen no sign of rat survivors.
On March 23rd, after weeks of storm delays, Martin watched a helicopter fly out to strafe the island with the final load of poison bait. “It’s strange,” he said. “I’ve thought about this moment for the last six years — it consumed my life. I imagined we’d be exultant when the last load went out, but we were completely flat. We just stood there thinking, now what?”
He’s hoping for more eradication projects, bigger projects. He’d like his team to travel the world, “a kind of baiting flying circus,” he said. When I spoke with him, he was optimistic, having just read a paper in the journal Biological Conservation imagining what the next generation of rodent eradication might look like.
The paper outlines an arsenal of possible technologies. There are automatic traps like the Spitfire, which sprays sticky poison onto rats when they pass through a tube, killing them when they lick it off, and the A24, which uses a CO2-fired piston to smash their skulls. Species-specific poisons could be dropped by drones day and night. Maybe the most ambitious method involves the release of transgenic rats, engineered so that their progeny would be entirely male. If their offspring were capable of spreading the transgene, it could theoretically drive rats to near extirpation without the use of poison. Their incredible fecundity would finally be thwarted, and after several generations, a horde of bachelor rats would fight amongst themselves, dwindle, and disappear.