Rat Island appears to be rat-free

ALEUTIANS: With vermin believed gone, seabirds returning to nest.

August 23, 2009 

Two helicopters, each slinging a bucket, were used to spread bait on Rat Island. Project members are now concerned that some of the poison may have affected other wildlife, particularly seabirds.

STEVE EBBERT / ALASKA MARITIME NWR

WASHINGTON -- After two centuries of an epic infestation, Alaska's Rat Island may finally merit a name change.

The island, 1,300 miles west of Anchorage in the 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 on the Alaska Maritime National Wildlife Refuge's research vessel, the Tiglax, 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 rats are still present nearly one year after crews dropped 700 pounds of poison-laced pellets. A research team will return next year to be sure they killed all rats, but MacLean said it wouldn't be unreasonable to consider calling the island by what is believed 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. "There would be nothing better."

Because Rat Island has been infested with rats for 230 years, it's difficult to know exactly what its ecosystem was like before the rat invasion. There are no other land-based mammals on the island, so the 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 with 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. Without that diversity, Rat Island has long lacked the same cacophony of bird calls heard on other islands in the refuge.

"It was eerily silent, the birds were just not there," MacLean said.

WORLDWIDE INFESTATION

Worldwide, an estimated 90 percent of islands have been invaded by rats, particularly those of the Norway variety. Rats may be responsible for an estimated 40 to 60 percent of all recorded bird and reptile extinctions on islands, according to Island Conservation, the 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 once inhabited it centuries ago. The 10.7-square mile island is about 200 miles west of Adak, the nearest island inhabited by humans.

In Alaska, some coastal areas were infested by rats 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. They're so unwelcome that the Municipality of Anchorage -- its port so far is rodent-free -- bans possession of 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. It is illegal for a vessel with rats to enter all Alaska waters.

"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 successfully removed non-native foxes introduced by Russian trappers. Rat Island itself 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."

MORE TO COME

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 the program on other islands in the 1,100-mile island chain, where as many as a dozen other islands remain overrun with rats.

The project has had some ecological side effects, however. Scientists found more than 250 dead birds on Rat Island this 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 some gulls would die, but 43 bald eagle deaths surprised and disappointed them. Bald eagles are plentiful in the Aleutians, and unlike in the Lower 48, 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.

MOVEMENT STUDIED

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

They have several theories, but 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 the gulls and eagles --both scavengers -- ate them, but it is possible. It's unclear how many rats were killed, again, because most perished in burrows.

"Our objective was the number zero at the end," MacLean said.

On Rat Island, however, eagle populations are expected to climb again, especially if seabirds increase in their numbers, giving the eagles more prey. Already, scientists are seeing signs that seabirds are returning and nesting, Byrd said. They'll keep monitoring it, though, because the birds only lay two to three eggs and it takes several years for those hatchlings to become parents themselves.

To determine what sort of birds were present on the island, archeologists with the wildlife refuge have been studying middens - ancient refuse piles - left by the island's previous Aleut inhabitants. Based on the bones in those dumps, they can determine what birds the islanders ate, and therefore, which species were present on the island.

If birds do not successfully return on their own, they will consider colonizing them with hatchlings from other islands.

What they've seen so far, however, has been promising: Aleutian cackling geese, ptarmigan, peregrine falcons and black oystercatchers have been spotted nesting on the island.

It's one big circle, said Byrd. The more birds, the more bird waste. That means more fertilizer for the vegetation on the island. More vegetation means better nesting conditions for all of the birds on the islands. That means more birds.

"The birds that were nesting this June were nesting for the first time in 230 years without rat predation," Byrd said. "We don't expect the population to return in year one. But we saw evidence they were nesting, and some successfully. Those chicks wouldn't have made it if rats were present."

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