South Georgia is a remote, inhospitable island clinging on in the southern Atlantic Ocean. Despite the hostile climate, the ocean waters around South Georgia are extremely productive and provide food for millions of sea birds and marine mammals. For the huge numbers of birds that feed in the southern Atlantic, South Georgia is the place they call home. 29 species of bird breed on the island, including the wandering albatross, king penguin and the South Georgia pipit, which is found nowhere else in the world.
Unfortunately South Georgia has been colonised by invasive rodent species. These introduced rodents feed on the eggs and young of ground-nesting native birds, which can offer no resistance. Every year thousands, perhaps millions, of young birds are eaten alive by rats. Rats and mice were first brought to South Georgia by whaling ships in the 19th Century. Since then, with no natural predators, they have proliferated on the island. To see the damage these rodents can do, have a look at ARKive’s rather grim, but fascinating video of an introduced rat predating on a Henderson petrel chick. Henderson Island is similar to South Georgia: it is a remote, inhospitable island that supports a high diversity of – often threatened – bird life. On Henderson Island, as on South Georgia, rodents have a devastating impact on native bird populations.
South Georgia Heritage Trust, which is responsible for wildlife conservation on South Georgia, recognises that the only way to ensure the survival of native birds is to fully eradicate rats from the island. Previous research has shown that the only feasible method of eradicating rodents on an island the size of South Georgia – 80,000 hectares – is to spread toxic bait by helicopter. This is a massive undertaking and, if successful, South Georgia will be the largest island ever cleared of rodents. The eradication programme is aided by South Georgia’s geography: the island is divided by glaciers into several zones. Rodents can’t cross these glaciers, meaning that they will not re-infest baited areas.
The eradication programme began in March and conservationists reported that the first phase has been a success. Around 50 tonnes of rodenticide were spread by helicopter in March, over around 13% of the island. Inspections have found no evidence of live rats in this area – a great outcome. Although some wildlife will inevitably be harmed by the rodenticide, the shape, colour and size of pellets have been carefully designed to minimise their attractiveness to non-rodents.
Project leader Professor Tony Martin, from Dundee University, states that while losses to other wildlife are unfortunate, they are offset against the benefit to nesting bird populations. Professor Martin told BBC News ‘When Captain Cook first set foot on the island in 1775 this was perhaps the most important seabird breeding island in the world. By far the majority of birds have been removed by one agent rats which man introduced. What we’re doing is turning back the clock two centuries to try to get the island back to where it was; and its something we do believe can be accomplished.”
South Georgia Heritage Trust’s objective is to remove every rodent from every piece of land on South Georgia, and leave it rodent-free for generations to come. Hopefully, this will allow seabird populations to thrive on the island once more. To find out more about the rat eradication project, visit the South Georgia Heritage Trust’s website.