GIANT mice are causing an ecological disaster on a South Atlantic island by eating the chicks of the endangered sea birds that nest there.

More than a million albatross, shearwater and petrel chicks are being killed each year on Gough Island, eaten alive by overgrown rodents, scientists said yesterday.

Though the mice are three times larger than their European cousins, weighing as much as 1.41oz (40g), they are dwarfed by the fledgeling sea birds that have become their prey. An albatross chick weighs up to 22lb, some 250 times the weight of the rodents.

The birds, however, are virtually immobile and must be protected from attack by adults, who spend many hours away fishing for food. The mice gnaw the live chicks, their wounds become infected and they die. “It is like a tabby cat attacking a hippopotamus,” said Geoff Hilton, a senior research biologist with the Royal Society for the Protection of Birds (RSPB).

“We think there are about 700,000 mice, which have somehow learnt to eat chicks alive — much like blue tits learned to peck [through] milk bottle tops.

“Gough Island hosts an astonishing community of seabirds and this catastrophe could make many extinct within decades.”

The British island, part of the Tristan da Cunha group, is uninhabited by human beings but home to 99 per cent of the world’s Tristan albatross and Atlantic petrel populations. These birds are the most frequently attacked. Only 2,000 Tristan albatross pairs remain.

The chicks are particularly vulnerable because the mice are not native to Gough Island; ornithologists think that it was selected as a breeding site because of its lack of mammalian predators.

Because the fledgeling birds evolved in an environment that was free from predators, they have not developed ways of defending themselves.

When the chicks are first attacked, the scent of blood seems to be detected by other mice, which also then feed on the stricken birds. Film footage has shown as many as 10 to 15 mice attacking a single bird.

Richard Cuthbert, another RSPB researcher, said: “The albatross chicks spend eight months sitting waiting for food from their parents. They are nearly a metre tall and 250 times the weight of the mice but are largely immobile and cannot defend themselves.

“Without predators present this would not be a problem but for a carnivorous mouse population on one of the wettest and windiest places on Earth it is an easy meal of almost unimaginable quality. The result is carnage.” His colleague Ross Wanless said: “There are mice on other South Atlantic islands, but Gough is the only site where this is known to be happening.”

Scientists believe that at least a million chicks a year on Gough are being killed by mice, including 700,000 Atlantic petrels and about 1,000 Tristan albatrosses.

The Gough mouse is one of 2,900 non-native species damaging native wildlife on the 17 UK Overseas Territories and Crown Dependencies, the Joint Nature Conservation Committee has found.

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