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By Jan TenBruggencate Advertiser Science Writer

HONOLULU, Hawai‘i (October 11, 2000 - Honolulu Advertiser)---Kure Atoll’s 260-acre Green Island is finally rat-free, but faces a huge new problem – aggressive alien ants are killing off native insects, spreading scale insect pests and threatening the whole ecosystem.

Entomologist Gordon Nishida of the Bishop Museum in Honolulu conducted a series of samplings after seeing large numbers of bigheaded ants. He found sites on the island average 26,500 ants per square meter – just on the surface.

"It’s an incredible number," he said.

Green Island is as isolated a speck of land as you’re likely to find. It is a flat chunk of coral and sand, situated at the edge of the atoll reef, 1,300 miles northwest of O‘ahu.

The Coast Guard for many years had a LORAN navigation station on the island, which is lashed by harsh winter storms. It was isolated duty, and those at the station had only turtles, seals and tens of thousands of seabirds for company.

When the Coast Guard left and the state took over the island as a wildlife refuge, one of the first challenges was the rats that had been prevalent here for more than a century, probably inadvertently left by early visiting sailors or shipwrecks. The problem: the rats were eating seabirds and their eggs.

The state Department of Land and Natural Resources in 1993 launched an eradication effort using poison bait. Within a year, it was not possible to find evidence of rat activity. Wildlife officials annually survey the island, checking the carcasses of birds that have died of other causes.

The most recent survey, taken during the past week as part of the Northwestern Hawaiian Islands reef survey, found no indications that rats survive.

"There has been a marked increase in the numbers of Christmas shearwaters, Bonin petrels, wedge-tailed shearwaters and red-tailed tropic birds," said Ethan Shiinoki, a state wildlife researcher.

The new issue is the ants. It is not clear when they arrived, but they could be as big an ecological hazard as the rats were.

"Big-headed ants are known exterminators of other insects … Native insects would have no defenses against these ants, therefore would be easy prey, and their astonishing numbers here would probably affect even non-native species," Nishida said.

The ants also co-exist with an alien scale insect, from which they collect honeydew or nectar. While the scale is damaging alien plants, it is also beginning to affect native naupaka. Since the ants feed on the honeydew, they protect the scale insects from things that might attack them.

"They’re ecosystem busters. Ants are incredibly effective and efficient predators and have few limits on their diet. They’ll eat anything that doesn’t have a defense," said Beth Flint, a U.S. Fish and Wildlife Service biologist.

The researchers do not yet know how much worse the ant infestation can get, and hope to find money to study the problem. If the ants attack ground-nesting seabirds, one of the key reasons for having the wildlife refuge will be destroyed.

"Kure is an important place for wildlife, particularly seabirds, but the ants could really change that," Nishida said.

For additional reports from The Honolulu Advertiser, go to PACIFIC ISLANDS REPORT News/Information Links: Newspapers/Honolulu Advertiser.

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