Giant house mice are devouring millions of endangered seabird chicks on a remote South Atlantic island, a new study confirms.
The carnage by rodents previously thought harmless to seabirds may be pushing some of the birds to extinction on Gough Island, a British territory a thousand miles off the coast of South Africa.
The island considered the world's most important seabird colony is breeding ground to roughly 10 million birds of more than 20 species including the the Atlantic petrel.
The study found mice are out of control on the island and threatening to wipe out several of the world's rarest bird species.
"The sheer densities of the numbers of birds there—that's why Gough Island is so special," said study co-author Ross Wanless, of the University of Cape Town. "But the mice seem to be chewing away through those."
Studies suggest that the albatross chicks which ironically weigh nearly 300 times more than rodents are unable to fend off these novel predators.
Mice feast on endangered island birds
Apart from a small team running a weather station, there are no humans living on the island. Meanwhile, mice introduced to the island in the nineteenth century have multiplied to about 1.9 million.
Moreover in the absence of predators, the rodents have grown 50 times bigger than ordinary house mice reaching up to 10 inches (27 centimeters) long, excluding the tail.
Especially during the winter months as the food sources deplete, the rodents adapt their diets to include feasting on baby birds. Studies suggest that the albatross chicks which ironically weigh nearly 300 times more than rodents are unable to fend off these novel predators.
Mouse's effect on the Atlantic petrel
To get an insight into how the mouse attack the Atlantic petrel, given that the species nest underground the researchers studied the mice on Gough Island.
For four breeding seasons, Wanless and his team tracked 178 petrel nests with the help of infrared cameras to monitor the invasive rodents.
Weekly footage of the nests revealed that of the 1.6 million petrel chicks born each year, 1.25 million are devoured by mice.
Wanless stated, "Essentially, these are babies. If you put an extremely hungry rat in a room with a human baby, [the infant] wouldn't be able to defend itself."
"It's the same with these chicks. The birds have no idea what's coming, because they've never been exposed to anything that will enter their burrow."
Experts theorize that the mice could be eradicated by dropping poison bait from helicopters.
"I've seen how unbelievably hungry these mice are," Wanless said. "I know without a shred of doubt that if you put food out at the right time of year, those mice would eat it."
The new study was published online May 8 in the journal Animal Conservation.