"They pretty much made the island worthless for a lot of wildlife," said Art Sowls, a biologist with the Alaska Maritime National Wildlife Refuge, which sprawls across the Aleutians and other Alaska islands.

Rodents have reigned at Rat Island at the western end of the Aleutians since the 1780 shipwreck of a Japanese sailing ship, wreaking havoc on millions of seabirds with no natural defenses against land predators.

The US Fish and Wildlife Service, which manages the Maritime refuge, is drawing up plans to wipe out Rat Island's rats. A formal proposal is expected in about a month, according to Sowls.

The agency is trying to find an effective way to wipe out rat populations without harming other wildlife. Rat Island is a good starting point, according to biologists, for a removal program because it is small without much other wildlife.

Rats are a problem shared by remote islands all around the world. Biologists said successful rat removal programs have taken place in more than 250 islands including Campbell Island south of New Zealand and Langara Island in British Columbia.

"A lot of people go, 'Oh they're just rats, what's the big deal?'," said Ron Clarke, assistant wildlife conservation director at the Department of Fish and Game.

Once informed about the environmental destruction wrought by rats, citizens are generally determined to avoid them. Rats are blamed for causing about half the extinctions of various species worldwide since the 1600s and are persistent nuisances once established, said Clarke.

"They're very good swimmers. They'll eat anything. They're just very good at surviving," Clarke said.

SWEEPING RAT MANDATES

Alaska state officials have issued sweeping new regulations that slap rat-prevention mandates on Alaska ports and harbors that have served as entry points for invading rodents. The removal plan and new state regulations are extensions of previous anti-rat policies in Alaska.

Since the early 1990s, wildlife refuge managers have maintained a "rat-spill" program -- in which emergency responders prevent the spread of rats from shipwrecks -- similar to oil-spill contingency plans maintained by state and federal agencies.

"It's entirely possible that in a shipwreck situation, the environmental damage created by the introduction of rats into the environment would be even worse than that of a major oil spill," Sowls said.

He cited the situation on the Aleutian island of Kiska, which still holds a colony of millions of auklets, a small seabird, but where introduced rats are decimating that natural population.

Researchers commonly find vast stretches on Kiska with no live birds, only rotting bodies stuffed into burrows.