Why an Alaska island is using peanut butter and black lights to find a rat that might not exist

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.

Shortly after receiving the resident's report in June, wildlife officials arrived at the apartment complex and crawled through nearby grasses, around the building and under the porch, looking for tracks, chew marks or droppings. They baited traps with peanut butter and set up trail cameras to capture any confirmation of the rat's existence — but so far have found no evidence.

"We know — because we've seen this on other islands and in other locations in Alaska and across the world — that rats absolutely decimate seabird colonies, so the threat is never one that the community would take lightly," said Lauren Divine, director of the Aleut Community of St. Paul Island's ecosystem conservation office.

The anxiety on St. Paul Island is the latest development amid longstanding efforts to get or keep non-native rats off some of the most remote but ecologically diverse islands in Alaska and around the world.

Rodents have been removed successfully from hundreds of islands worldwide — including one in Alaska's Aleutian chain formerly known as "Rat Island," according to the U.S. Fish and Wildlife Service.

But such efforts can take years and cost millions of dollars, so prevention is considered the best defence.

Around the developed areas of St. Paul, officials have set out blocks of wax — "chew blocks" — designed to record any telltale incisor bites. Some of the blocks are made with ultraviolet material, which allow inspectors armed with black lights to search for glowing droppings.

They also have asked residents to be on the lookout for any rodents and are seeking permission to have the U.S. Department of Agriculture bring a dog to the island to sniff out any rats. Canines are otherwise banned from the Pribilofs to protect fur seals.

There have been no traces of any rats since the reported sighting this summer, but the hunt and heightened state of vigilance is likely to persist for months.

Divine likened the search to trying to find a needle in a haystack "and not knowing if a needle even exists."

The community of about 350 people — clustered on the southern tip of a treeless island marked by rolling hills, rimmed by cliffs and battered by storms — has long had a rodent surveillance program that includes rat traps near the airport and at developed waterfront areas where vessels arrive, designed to detect or kill any rats that might show up.