Rat Island rid of namesake pest

Scientists dismayed at ecological side effects

Posted: Monday, August 24, 2009

WASHINGTON - After two centuries of an epic infestation, Alaska's Rat Island finally may merit a name change. The island, part of a national wildlife refuge in the sprawling Aleutian chain, appears to be pest-free for the first time since rats overran it after a Japanese sailing ship wrecked there in the late 1700s.

Scientists stopped by in early August to check on the progress of the $3 million eradication. So far, "no sign of rats whatsoever," said Steve MacLean, the polar marine program director for The Nature Conservancy in Alaska, one of the partners in the rat-ridding effort.

No gnawing was apparent on the waxy, peanut butter-infused bait blocks that, if bitten, would signal that rats are still present nearly a year after crews dropped 700 pounds of poison-laced pellets. A research team will return next year to be sure they killed all the rats, but MacLean said it wouldn't be unreasonable to consider calling the island by what's thought to be its original name, Howadax, which means "entry" or "welcome" in the Aleut language.

"We would love nothing better than to return an Aleut name to the island," he said.

The project has had some ecological side effects, however. Scientists found more than 250 dead birds on Rat Island last spring when they returned for the first time since the island was baited. Those carcasses tested positive for brodifacoum, the poison used on the rats. Scientists had anticipated that some gulls would die, but the deaths of 43 bald eagles surprised and disappointed them.

Bald eagles are plentiful in the Aleutians, and, unlike in the Lower 48 states, were never listed as an endangered species in Alaska. Alaska has more than 50,000 bald eagles, and the birds were delisted nationwide in 2007.

The Fish and Wildlife Service will look at water and soil samples to understand the movement of the rat poison in order to determine how it killed so many birds, and what scientists need to do to avoid such deaths next time, if they treat other islands in the chain.

There are several theories, but scientists suspect that gulls ate some of the poison pellets. Eagles may have eaten the dead gulls. The poison, an anticoagulant, causes internal bleeding that kills the rats. Because the rats died mostly in their underground burrows, it's less likely that the gulls and eagles - both scavengers - ate them, but it's possible. It's unclear how many rats were killed, again, because most perished in burrows.

Since Rat Island has been infested with rats for 230 years, it's difficult to know exactly what its ecosystem was like before the rodent invasion. With no trees for nesting, and no other land-based mammals, the unwelcome rat refugees ate their way through the eggs and chicks of the ground-nesting seabirds.

Neighboring rat-free islands in the Aleutians have a more abundant and diverse seabird population, said Vernon Byrd, a senior biologist at the refuge. Those other islands have about a half-dozen more types of burrow-nesting seabirds, including horned puffins, Leach's storm petrels and whiskered auklets.

Rats, particularly those of the Norway variety, have invaded an estimated 90 percent of islands worldwide. They may be responsible for an estimated 40 percent to 60 percent of all recorded bird and reptile extinctions on islands, according to Island Conservation, a California-based group that partnered with The Nature Conservancy and the U.S. Fish and Wildlife Service to rid Rat Island of its namesake inhabitants.

Last September's rat-baiting operation was a logistically challenging project involving scientists from the refuge and the two conservation groups, and a pair of helicopters operated by pilots trained in similar successful rat-eradication projects in New Zealand.

The goal of the partnership, which got federal earmarks but was funded mostly by private donors, is to rid the ecosystem of invasive species and restore Rat Island's natural ecosystem.

Other than researchers, few modern humans have any reason - or opportunity - to visit Rat Island, although native Aleuts inhabited it centuries ago. The 10.7-square-mile island is 1,300 miles west of Anchorage and about 200 miles west of Adak, the nearest island inhabited by humans.

Rats infested some coastal areas of Alaska when military vessels visited in World War II, but much of the state is free from rats, said Joe Meehan, the lands and refuge program coordinator for the Alaska Department of Fish and Game. Rats are so unwelcome that the municipality of Anchorage - its port so far is rodent-free - bans the possession of most rats. Many ports, including St. Paul Island in the Pribilof Islands, ban boats with rats aboard from entering city waters or tying up at the dock.

"Rats are bad. They're bad for wildlife; they're bad for people," Meehan said. "They obviously decimate bird populations. They can spread disease to wildlife. They can devastate ecosystems that are dependent on seabirds."

The Fish and Wildlife Service already has seen the positive effects of similar ecosystem restorations on 40 other Aleutian islands, where scientists removed non-native foxes introduced by Russian trappers. Rat Island had foxes removed in 1984.

"The way we view it is that one island at a time, we're trying to restore the natural conditions, at least on land," Byrd said. "That means plants, animals, marine mammals, birds and fish. Every one we can restore, we see as a link in this chain that's healthy again. It's a lot healthier system without the holes, which are like wildlife deserts."

If their efforts on Rat Island prove successful, it would be the third-largest island in the world to be rendered rat-free. Some 300 islands worldwide have been rid of rats, most recently Anacapa Island in California's Channel Islands National Park. If the Rat Island project works, the Fish and Wildlife Service hopes to replicate it on other islands in the 1,100-mile island chain, where as many as a dozen other islands remain overrun with rats.



CONTACT US

  • Switchboard: 907-586-3740
  • Circulation and Delivery: 907-586-3740
  • Newsroom Fax: 907-586-3028
  • Business Fax: 907-586-9097
  • Accounts Receivable: 907-523-2230
  • View the Staff Directory
  • or Send feedback

ADVERTISING

SUBSCRIBER SERVICES

SOCIAL NETWORKING