A SCHEME to eradicate brown rats in a bid to protect an internationally important population of seabirds would cost £4.6 million, it has emerged.

The Isle of Rum is home to around a quarter of the world's breeding Manx Shearwater seabirds but conservationists fear that the abundance of brown rats on the island poses a risk.

Scottish Natural Heritage has now carried out research on the threats posed by the brown rats and discovered the cost of removing the animals from the island would reach around £4.6m.

Chris Donald, SNH South Highland operations manager, said: "The report highlights some of the issues that we face in ensuring that we have a healthy and thriving biodiversity on Rum. Any scheme to remove the rats would be extremely costly. All eradication schemes, no matter where, are expensive.

"Removal is a valuable tool that we can use if necessary. Invasive rodents have been implicated in declines and extinctions of seabird populations worldwide. However the impact of rat species is regarded as one of the most significant global threats to seabirds.

"So we need to consider our next moves amid the knowledge that hundreds of rodent eradication campaigns have been undertaken on islands worldwide."

Brown rats have already been eradicated from Canna to restore breeding habitats for Manx shearwaters and other seabirds.

However, that project cost just £600,000, compared with the £4.6m estimated price for their removal from the 41 square miles of Rum.

Canna's rabbit population also boomed after the project to eradicate rats, reaching more than 16,000 at one stage, and more money had to be spent to cull the animals, which were blamed for causing a landslide that blocked a main route on the island.