A Norway rat has left this least auklet nearly headless on Alaska's Kiska Island.

Traveling with humans as stowaways on ships, three rats species native to Europe and Asia have become established on roughly 90 percent of the world's major islands and island chains, experts say.

"No species is safe when rats arrive," said Alan Saunders, director of the Cooperative Islands Initiative at the University of Auckland, in New Zealand.

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