Biggest ever rodent cull gets underway

The biggest rat eradication campaign in history is yielding promising results, conservationists on the small Atlantic island of South Georgia have declared.

Eventually, millions of the vermin will be culled under the program, which aims to protect the southern Atlantic island’s native bird population.

Rats were introduced to South Georgia via whaling and sealing ships in the 19th and 20th centuries and quickly took over the island’s ecosystem, which is prized for its remarkable diversity of bird life. There are now thought to be millions of the rodents, which have devastated the natural wildlife.

More than 50 tons of toxic bait have been dropped from helicopters in a zone hemmed in by glaciers, the BBC has reported. Inspections of the ground revealed dead rats but showed the poison had not affected any other wildlife.

The culling area represented only the first phase of the program, covering just 13 percent of the rat-infested land.

The South Georgia Heritage Trust told the BBC it was strongly encouraged by the early results.

"Prior to the baiting, if you went out at night, there were rats running everywhere," said project leader Professor Tony Martin from Dundee University in Britain. "A week after the bait went down — not a sign of a single rat. We even put out little batches of bait pellets that were particularly attractive to the rats. We saw them being taken for the first few days, and then there were no more pellets taken."

South Georgia is a British territory. It was first surveyed by the explorer James Cook in 1775. Thousands of tourists visit the 107 mile-long island to see its seals, penguins, albatrosses and other birds.

But since the brown rats began leaping off the ships and ran riot on the island, they have eaten their way through tens of millions of ground-nesting birds’ eggs and chicks. Rats eat the bird chicks alive, including albatrosses, petrels, prions – even chicks several times their own size.

Several species of bird, including the South Georgia pintail and the Cape petrel, are now under threat, while the island’s only songbird, the pipit, faces extinction.

"These simply will not nest in the presence of rats," said Dr Mike Richardson who chairs the steering committee of the South Georgia Heritage Trust Habitat Restoration Project.

"Rats have driven them into small refuges, which tend to be the small offshore islands around South Georgia's coast. But on the mainland, all along its north coast, South Georgia has become a no-go area for these birds."

The eradication program is the largest ever attempted. Normally such a massive campaign would be impossible because the rats would travel back and forth and repopulate previously cleared areas. But the sub-Antarctic island is marked by numerous glaciers that divide up the territory into convenient killing zones that can be cleared one by one.

The rats cannot cross the glaciers, so conservationists can be sure rodents from neighbouring zones will not re-infest baited areas at a later date.