On an island of windswept tundra in the Bering Sea, hundreds of miles from mainland Alaska, a resident sitting outside their home saw — well, did they see it? They were pretty sure they saw it.

A rat.

The purported sighting would not have gotten attention in many places around the world, but it caused a stir on St. Paul Island, which is part of the Pribilof Islands, a birding haven sometimes called the “Galapagos of the north” for its diversity of life.

That’s because rats that stow away on vessels can quickly populate and overrun remote islands, devastating bird populations by eating eggs, chicks or even adults and upending once-vibrant ecosystems.