A century passed, and by all appearances, activity on the island proceeded as it had for hundreds of years. In March 1990, a Ph.D. student named Bernie
Tershy set up camp there to study the island's seabirds--he was struck by something surprising. All over the island, black rats menaced the birds; they
infiltrated the colonies, pilfered the eggs, and preyed on the young. At some point during the guano excavations--likely as one of the many supply ships
hugged the rocky coast--the rats had scampered ashore. Now, all these years later, as Tershy tracked the birds, he watched helplessly as the rats ate his
data. "The birds get oil for their feathers from a gland above their tails, and rats like that. It's one of the places they like to start," he explained.
They also go for the middle of the back, where "they can run up and chew, chew, chew, and the birds have a hard time shaking them off."
The island was never intended to accommodate rats. With no predators to keep them in check, Tershy knew the rats would just keep killing the defenseless
seabirds until the colonies ceased to exist--these birds, that bred only on this rock and a handful of others scattered across the ocean, didn't stand a
chance. Perceiving the situation as grossly unfair, Tershy began to think of ways he might relieve the toll the rats were taking.
In the back of his mind was a story he'd heard. In 1958, an ornithologist at the National History Museum of Los Angeles County named Kenneth Stager visited
Clipperton Island, a tiny desert atoll in the Pacific Ocean. He'd gone expecting to observe what early explorers had described as massive colonies of
tropical seabirds, but what he found shocked him. Feral pigs left by a failed human settlement had decimated the flocks, leaving a mere 650 birds by
Stager's count. The survivors had crammed themselves onto an abandoned ship and some rocky ledges offshore, the only surfaces safe from the pigs' reach.
Stager was what Tershy calls an "old-school ornithologist," so naturally he'd brought a shotgun with him. He had planned to use it to collect a few of the
birds, but instead, shot every last pig he could find. Thirty years later, when Tershy visited Clipperton, it had transformed. The seabirds were back,
nearly 140,000 strong, as were millions of large, orange land crabs that the pigs had also done in. Stager, in his thoroughness, had staged a one-man
eradication, allowing Tershy to find an ecosystem with no trace that humans had ever been there. Admiring Stager's brazen willingness to take action,
Tershy wondered if he might somehow replicate his success.
He brought his idea to a friend, a biologist named Don Croll, who studied seabirds and whales. The two had met in California in the '80s and had been
collaborating on research projects ever since. Croll had had his own encounters with rats ravaging colonies on islands in Antarctica, and was instantly
keen to Tershy's idea.