The oil that spilled from the Exxon Valdez killed hundreds of thousands of marine animals. But biologists say the ships that ply state waters often carry a cargo that could prove even more devastating to plant and animal life--rats.
"If a ship goes aground on a major sea bird colony, the resulting damage could be far worse to marine life than the (1989) Exxon oil spill," said Art Sowls, a biologist with the U.S. Fish and Wildlife Service.
A small group of wildlife service biologists in Alaska, who have dubbed themselves the "rat pack," are developing plans to protect the state's fragile island ecosystems from the rodents, which are inadvertently introduced into the environment when sea vessels dock or run aground.
Tony DeGange, another fish and wildlife service biologist involved in the project, said the group is just beginning to write proposals and try to secure money for their plans.
Most island wildlife evolves without predators and is therefore very susceptible when rats enter the ecosystem, DeGange said.
The rodents feed on the eggs and chicks of birds. DeGange said they are capable of wiping out an entire sea bird species on an island. Rats also prey on fauna and, once loose, reproduce rapidly. In addition, they are tenacious and reclusive.
"The effects of oil spills are relatively short term compared with what can happen with rats on an island," he said. "You may never get them off."
For that reason, biologists are concentrating their preventive efforts on areas they believe are mostly free of rats, including the Pribilof Islands and the hundreds of uninhabited keys in the Aleutians.
DeGange said the methods biologists employ will vary, depending on whether an island or group of islands is inhabited.
The inhabited Pribilofs--St. George and St. Paul--are home to about 2.5 million nesting birds and a million fur seals, Sowls said.
The tiny Bering Sea islands, about 300 miles off the west coast of Alaska, are experiencing a boom in the fishing industry.
"The development is so quick it's almost like a military invasion," Sowls said. "It's great for the economy, but a real challenge to the environment."
Biologists aren't sure whether rats could thrive in the Pribilofs' harsh Bering Sea conditions, but DeGange said with the increased development they don't want to take any chances.
They plan to teach people how to use rat poisons and have them set bait and trap stations in the harbors of St. George and St. Paul.
Keeping rodents off the uninhabited islands in the Aleutians and other areas of the state pose a different, and potentially trickier, problem for biologists.
There are millions of sea bird colonies in the Aleutian Chain, DeGange said, and though many of the islands are remote, uninhabited and undeveloped, major shipping lanes pass within a few miles.
If a ship were to wreck, he said, biologists would have to act quickly to determine whether the vessel probably contained rats, and if it did, how to respond.
Smaller ships like crabbers don't pose much of a problem, but DeGange said bigger vessels that travel long distances, such as grain ships, are likely to have rats.
"If a grain ship went aground, my guess is we'd get out there as fast as we could," DeGange said.
With more funding and research, biologists hope to be able to use more complex eradication methods soon, such as anticoagulants to get rid of rats if a ship runs aground.
The advantage of anticoagulants, which cause internal hemorrhaging, is that rats don't seem to build up the immunity they develop to other poisons, DeGange said.
Rats also can learn to avoid standard traps, he said.