The mostly abandoned town of Grytviken on South Georgia island. Cropped from original panorama.
Photo: Jens Bludau (Wikimedia Commons)

Exterminators have successfully cleansed the remote British overseas territory of South Georgia island in the South Atlantic of invasive rats that, since the year 1775, had been feasting on the eggs and chicks of two species of birds found nowhere else on the planet and many others.

The successful, $13.5 million (10 million pounds) rodent purge is in large part thanks to the work of the South Georgia Heritage Trust, which declared the island officially rat-free this week, New Scientist wrote. There are 33 species of birds on the island, all of which like any creature could benefit from not having swarms of rats attempting to rip apart their young. But removing the rats is particularly critical to the long-term survival of the South Georgia pipit and the South Georgia pintail, which along with the millions of other birds on the completely tree-bare island must nest on or under the ground.

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The project involved extensive use of helicopters to cover the island with rodent bait, with the active phase of the project dating all the way back to 2011, New Scientist wrote:

Since 2011 teams have braved hostile conditions, through rain, snow and extreme winds, to undertake three phases of dropping bait on vegetated areas where rodents are found, which are separated from each other by glaciers.

Three helicopters, including one that was once registered to Jackie Onassis, were used to drop bait from hoppers across 108,723 hectares (269,000 acres) of the island – a range eight times bigger than any other eradication area tackled anywhere in the world, the trust said.

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To certify that the mass deployment of rodent bait had indeed been successful in eradicating the infestation, teams had to check over 4,600 detection devices to certify they showed no signs of rat activity, New Scientist added. They also brought in three trained dogs to sniff for any remaining rat enclaves.

According to the BBC, the project was in part possible because the numerous glaciers criss-crossing South Georgia island isolated rat populations in pockets that could be exterminated individually.

“We’ve been on tenterhooks; would there be a remnant enclave somewhere?” project steering committee chair Mike Richardson told the BBC. “But I’m pleased to say over the last six months, not a single sign of a rodent has been found. And so to the best of our knowledge, this island is now rodent-free.”

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Project director Dickie Hall added, “Dogs have an incredible sense of smell. They can detect rodent scent from several meters, or even tens of meters if conditions are right. So by walking through a piece of habitat, we can be very confident with these dogs of finding rodents if there are any present.”

While the island is now officially believed rat free, they could return at any time if even a single pregnant female is able to make it on to shore along with the thousands of tourists that arrive every year. The BBC wrote that tourists are now only allowed to land on rubber inflatable boats with luggage and clothes that have been inspected, and all government and military ships that come to shore will be required to have rodent traps and cargo screening by dog is now being tested.

Reinfestation from locals is not expected to be an issue, the Guardian writes, since its former population of 2,000 abandoned the place after the collapse of the whaling industry and the primary remaining occupants are “two scientific research stations run by the British Antarctic Survey.” According to Popular Mechanics, roughly two dozen full-time residents remain.

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[New Scientist/BBC]