Posted on: Monday, May 9, 2005

By Jan TenBruggencate
Advertiser Science Writer

In 2002 and again in 2004, the small island of Nihoa, 150 miles northwest of Kaua'i, was denuded by a type of locust that threatened plants, native insects and the general ecology of the remote island.

"There wasn't a leaf left on the island," said Beth Flint, supervisory wildlife biologist for the Fish and Wildlife Service's Pacific Remote Islands National Wildlife Refuge Complex.

Wildlife experts are trying to figure out what they can do to prevent future miniplagues by the grasshopper Schistocerca nitens, a native to Central America that is also called the gray bird locust or vagant locust.

It was first found in the main Hawaiian Islands in 1964, at Sand Island on O'ahu. It is not known whether the locust flew to other islands or hopped on and off passing boats, but by 1984 it had been found on Nihoa.

"For some reason it has suddenly started going through cycles during which it reaches high enough densities to defoliate most of the island," while it doesn't do so on other islands, said University of Hawai'i biologist Sheila Conant, who has extensively studied the bird life of Nihoa.

Perhaps the only creature that may benefit from the locust swarms is the endangered Nihoa millerbird, an insect-eater.

"Our millerbird counts are quite high. But we don't know whether that's because of all the locusts they eat or because they were easier to count due to the lack of leaves on plants," Flint said.

Bill Gilmartin, director of research for the Hawai'i Wildlife Fund, raised money for an April workshop in which world grasshopper experts were brought to Honolulu to discuss options for controlling the bug.

They concluded that the first thing needed is more information, including what combination of rainfall, temperature and other factors causes the grasshoppers to suddenly increase in numbers. Then there's finding something that can control the creatures without affecting the island's 35 native insects, which include grasshopper relatives.

One of the tough problems is that during much of the year, there's no safe way to get on the isolated, rocky island. Moving around on it is difficult and threatens burrowing seabirds.

Scientists say the need for a solution is great, since the grasshoppers already may be driving other Nihoa species toward extinction. One native endangered plant that they like to eat, an amaranth, has not been seen for years.

If you have a question or concern about the Hawaiian environment, reach Jan TenBruggencate at P.O. Box 524, Lihu'e, HI 96766; jant@honoluluadvertiser.com; or (808) 245-3074.