Cool Science

The Risk of a Rat Invasion

An oil spill in Alaska can ignite a media storm. Not so the accidental introduction of foreign plants or animals, though these events can also do long-term damage to local species.

In 1780, a Japanese fishing vessel wrecked off the coast of Hawadax Island, an uninhabited, six-square-mile member of the Aleutian Archipelago that separates the Bering Sea from the Pacific Ocean. From that ship, brown rats spilled out onto the shore and prospered, wiping away all the seabirds on the island in the process, which were defenseless against these foreign predators.

Only a few decades later, the rat population had flourished to such a degree on Hawadax that a Russian captain named it "Kryssei," which means rat in Russian, and the moniker stuck for centuries. Only in the last 10 years did biologists move in to eradicate the rats from Rat Island and restore the local bird population (and the island's local Aleut name).

Birds like the horned puffin are at great risk when rats are introduced to their habitats via shipwreck.

Today, scientists are concerned that a rise in ship traffic also increases the risk of similar introductions elsewhere in these waters with similarly devastating results for birds. In a new paper in the journal Biological Invasions, co-authored by WCS's Dr. Martin Robards, Regional Director for the Arctic Beringia Program, they analyzed the islands most in danger of facing such a future. The study looked both at an island's seabird population and, based on a number of different factors like the wind, tides, and vessel traffic, the likelihood of a ship crashing into it (see below).

From this assessment, the team deemed three islands in this area as being most squarely in the crosshairs of a potential rat invasion—St. George, Buldir, and St. Matthew.

The good news is that, compared to 1780, vessels today do some rodent prevention on board to try to avert accidental introduction. Efforts are being made on land as well. Robards says more steps can be taken to ensure a potential invasion is wiped out before it truly takes hold, including clear monitoring and notification protocols if rats are seen and preemptive rat trapping in places where ships may come ashore.

"We just need to stay vigilant," he says.