Well into the 20th century, the brown rat was a frequent stowaway aboard ships. That's how it came to settle in South Georgia, a remote island in the southern Atlantic, along with house pets and reindeer brought over by whalers. The dogs and cats didn't survive the harsh Antarctic winters, and the last reindeer were relocated. But the rats thrived, multiplying to plague proportions.

South Georgia is home to birds found nowhere else in the world, like the South Georgia pintail duck (pictured), and the South Georgia pipit, the only song bird found in the Antarctic region. Because trees are scarce, birds build their nests on the ground. That means their eggs and chicks are easy prey for looting rats.

In 2011, scientists on the island decided to do something about the plague. Working in three phases - separated by two-year intervals - they laid rat poison out across the entire territory. Conveniently, glaciers form natural barriers, meaning rats can't easily migrate to repopulate areas where they have been eradicated.

Logistics for the operation were masterminded from Grytviken, King Edward Point, one of the only settlements on the archipelago. Only 30 people live there during the Antarctic summer. They work mainly in the island administration, sometimes receiving cruise ships and overseeing the island's nature conservation programs.

British biologist Sarah Lurcock has been leading the rat eradication program with the South Georgia Heritage Trust from the very beginning. She also runs the museum in Grytviken, and every year receives thousands of cruise ship tourists eager to learn about the island's history and nature.

The rat eradication team used three helicopters to distribute their cargo across remote parts of South Georgia. Often braving severe weather conditions - with storms, snow and ice - the conservationists threw rat bait from the choppers. Two helicopters broke down during the campaign.

The rat bait only takes effect some time after it has been eaten. That's to give the rodents a chance to go back to their dens to die, and to prevent local birds like skuas, petrels and caracaras from feeding on the toxic carcasses. It's still unclear to what extent the poison could impact the island habitat itself.

At the end of each phase, the scientists set up peanut-butter flavored wax bait to check if any of the rodents had survived. If the bait shows signs of being gnawed, clearly not all the rodents have been killed. But so far, the wax has remained untouched.

If the bait remains uneaten, that should signal a major success for the scientists. But to be sure, dogs were brought in from New Zealand to help scour the island for survivors. It's the final test of whether the operation has worked. Here's hoping the hounds will come up empty-muzzled.