The gray bird grasshopper is little more than a minor pest in most parts of its range, but on tiny Nihoa, 150 miles west of Kaua'i, it takes on the mantle of its African cousin, the desert locust, famous as the cause of one of the biblical plagues.

A scientific team that visited the island in October found the island fairly wet, vegetation healthy and the grasshopper population moderate — perhaps 12,000 adults and twice as many nymphs, said Alexandre Latchininsky, a University of Wyoming entomologist who specializes in grasshoppers. But in recent dry years, the story was quite different.

"In 2000 the locusts were at plaguelike proportions," said U.S. Fish and Wildlife Service entomologist Mike Richardson. It was dry again in 2004 when Richardson visited and found the animals — alternatively called grasshoppers or locusts — were dense, were aggressively eating drought-stressed vegetation, and were also going after other food.

"The grasshoppers were attacking us occasionally," Richardson said. "They went after orange peels. And if I dropped those little goldfish crackers, they were eating them right off the ground."

Latchininsky said these grasshoppers seem to do relatively poorly in wet weather, perhaps because they are subject to fungus attacks. That may be why they haven't been a big problem in the main islands.

"This particular species is not considered a big pest elsewhere, although because of its big size, it may damage vegetation badly. On the main Hawaiian Islands, because of high humidity and lush vegetation, their impact is not pronounced, and they are just a part of local fauna," he said.

But when it's warm and dry, their numbers can explode.

"In 2004 Nihoa was very dry, and the vegetation was very meager. Grasshoppers, on the contrary, were present in high numbers, and they devastated all remaining vegetation very badly, including the Nihoa fan palm. ... There was concern that devastation of vegetation will trigger loss of other species," Latchininsky said.

U.S. Fish and Wildlife Service wildlife biologist Beth Flint said researchers believe the locust has had severe impacts on some species.

"It's a really alarming problem," Flint said.

She said there are stands of dead 'ohai shrubs on the eastern side of Nihoa, probably killed by being repeatedly defoliated during dry weather. 'Ohai is an endangered native legume, Sesbania tomentosa, with bright reddish flowers. It is found at Nihoa and the main Hawaiian Islands.

"They really like the 'ohai," Flint said. Other rare plant species are in very low numbers or may already be extinct, she said. Nihoa's native land birds, the Nihoa finch and Nihoa millerbird, appear not to have been significantly affected so far. Indeed, the millerbird may derive some benefit — it eats the grasshoppers.

A problem in understanding the impacts of the Nihoa locust comes with the isolation of Nihoa. Scientists visit infrequently, partly because it's far away, but also because access to the rocky island is difficult and often impossible due to dangerous surf. Most of the island's coast is near-vertical cliffs that drop straight into the sea. Scientists normally try to land on a rocky shelf on the south side.

But even if they could easily and frequently get to the island, it's not clear they could do much about the grasshoppers.

"Many ways people deal with these pests are not appropriate for Nihoa, because its environment is so fragile," Flint said.

Latchininsky said there is no consideration of removing them entirely.

"Eradication of grasshoppers is out of the question — it is simply impossible," he said. The most common method, using insecticides, potentially would harm too many other insects, and potentially the birds. The only thing that might work is the establishment during dry periods of poison bait stations formulated with compounds to attract the locusts but not other animals, Latchininsky said.

And even if the locusts were eradicated, there is no way to ensure they would not return — particularly if they share any of the flying power of their African cousins.

"In 1988, swarms of the desert locust crossed the Atlantic Ocean from West Africa to the Caribbean islands, covering 3,000 miles in 10 days. This shows the great migratory potential of the species from this genus, schistocerca, to which the Nihoan grasshopper belongs," Latchininsky said.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.