A real-life horror show is unspooling on a small island in the South Atlantic. Giant alien mice are attacking and eating baby birds, then cannibalizing one another. The mice are descendants of house mice (Mus musculus) that reached the remote island as stowaways on British whaling ships in the 19th century. Since then, the mice have evolved to almost three times their former size-from 15 grams to 40. Their diets have evolved too-from seeds and insects to young birds. The mice attack, singly or in groups, after dark, when adult birds leave their nests to look for food. The mice gnaw through the nests and then on the chicks' bodies. The chicks eventually die from loss of blood or organ failure. The mice even turn on other mice and eat them.rnGough Island is home to about 20 species of seabirds. Though the chicks are often bigger than the carnivorous mice-albatross chicks are 250 times larger-they haven't evolved any defenses against predators. "It is like a tabby cat attacking a hippopotamus," says Geoff Hilton, a biologist with the Royal Society for the Protection of Birds (RSPB) in the United Kingdom.
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