By Jonathan Amos
BBC News science reporter
"Supersize" mice are eating seabird chicks alive on Gough Island, one of the most important seabird colonies in the world, UK conservationists report.
The rodents are taking out one million petrels, shearwaters and albatrosses each year on the UK Overseas Territory in the South Atlantic.
The Royal Society for the Protection of Birds says the mice infestation puts some species in danger of extinction.
It hopes to find ways to control or even eradicate the rodents.
"Successful eradications in the past have used poisons, particularly in New Zealand; that is one option," said Dr Richard Cuthbert, a biologist with the RSPB.
"There are also potential diseases for mice we could introduce - the equivalent of myxomatosis for rabbits," he told the BBC News website.
Gough Island is some 8km long and 6km wide and is the most southerly of the Tristan da Cunha group.
It is used as a nesting ground by 22 bird species, of which 20 are seabirds; 10 million individuals can be found there at any one time.
Until passing sealing ships moored up in the 19th Century, the birds were largely safe from predators. But mice aboard the ships have infested Gough, and grown large, partly because of the abundant new food source on which they have recently started to indulge.
"Mice and other small animals often do get bigger when they are put on islands, particularly islands at higher latitudes," Dr Cuthbert explained.
"It's an ecological rule: if it's a cold environment, you are better off being a larger animal."
The albatross chicks spend eight months sitting waiting for food from their parents.
The adult will leave its chick alone for many months
They are nearly a metre tall and 250 times the weight of the mice but are largely immobile and cannot defend themselves.
The mice gnaw into the birds' flesh as they sit on the ground. Researchers have seen as many as eight or 10 rodents feasting on a single ailing chick.
It will turn around when under attack but cannot withstand such an assault.
On two fronts
Albatrosses are already endangered by industrial trawling. About 100,000 of the charismatic birds are thought to be killed each year when they are hooked on the longlines of fishing boats and pulled under the water to drown.
As a country which has ratified the ACap (Agreement on the Conservation of Albatrosses and Petrels) treaty, the UK would be expected to take action on Gough to sort out the mice problem.
"For the albatrosses on Gough, which hosts virtually the whole populations of several species, this just adds to the longlining problem - not only are they threatened at sea they are now also threatened on land," Dr Cuthbert said.
The injuries sustained are quite horrific
The Gough mouse is one of 2,900 non-native species damaging native wildlife on the 17 UK Overseas Territories and Crown Dependencies, a review by the Joint Nature Conservation Committee (JNCC) has found.
Dr Vin Fleming, who heads up the International Unit at the JNCC, told the BBC News website: "The British Overseas Territories stretch from the British Antarctic to Pitcairn, to the Caribbean territories and to all these South Atlantic ones.
"The numbers of non-native species range from up to almost 1,200 on Bermuda to zero on the South Sandwich Islands. As we saw from the recent Millennium Ecosystem Assessment, invasive species are responsible for the greatest loss of biodiversity on islands; and are second only to habitat loss globally as a major cause of extinctions."
The RSPB has been awarded £62,000 by the UK government's Overseas Territories Environment Programme to fund additional research on the Gough Island mice and a feasibility study of how best to deal with them.
Some of the rodents will be tracked to learn more about their behaviour, before a control programme is introduced.
NON-NATIVE SPECIES IN UK OVERSEAS TERRITORIES
Numbers cover plant, and vertebrate and non-vertebrate species
Abbreviations refer to: BIOT (British Indian Ocean Territory); BVI (British Virgin Islands); TCI (Turks & Caicos Islands); IOM (Isle of Man); BAT (British Antarctic Terr); SSI (South Sandwich Islands)
Figure of zero is probably a true zero for SSI but reflects a lack of information from the Cyprus sovereign base Areas