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The Washington Post

Hawaii Suffers An Amphibious Invasion

Plague of Noisy Frogs Annoys Islanders, Threatens Ecosystem

By William Booth

May 5, 2002
Copyright © 2002
The Washington Post Company. All Rights Reserved. 

WAHIAWA, Hawaii -- Night has fallen, the dogs are howling and screen doors are slamming along an overgrown alley in a working-class neighborhood of Oahu, as Nilton Matayoshi enters the hot zone.

"Helllloo? It's Nilton, with the ag department? Coming to look for frogs?" he calls out, taking care that he and his guest are not shot as backyard prowlers. The chief of chemical and mechanical control is carrying a large glass jar.

"Oooo, he's a loud one, eh?" Matayoshi says, impressed. Now he is close, real close. The frog's call grows as urgent as a lifeguard's whistle, and as relentless as a toddler with a question. Matayoshi sweeps his flashlight's beam up into the tall ginger by the lanai. There's something moist and brown in the bushes.

Hawaii has been invaded by a dun-colored, 2-inch-long, cute little frog native to Puerto Rico, called Eleutherodactylus coqui, or coqui for short. The name mimics the frog's two-note chirp -- ko-KEE! -- a trilling love song that has been described in the scientific literature as sounding like a car alarm. There are thousands of them, maybe millions, in Hawaii. They do not belong here.

Beloved as a cultural mascot in Puerto Rico, where the cartoon coqui adorns ashtrays and shot glasses for sale as keepsakes, the uninvited frog was condemned as an official pest in Hawaii last year.

The coqui represents a major potential disruption of the native ecosystems of Hawaii. There are no naturally occurring reptiles or terrestrial amphibians, no snakes, iguanas, toads or salamanders in Hawaii. Until the coqui arrived, it was a frog-free world.

The problem with adding frogs to the system is their voracious and indiscriminate appetite. Not only do the coqui consume insects that are necessary for pollination and other ecological chores, but the foreign frogs directly compete with native birds for insect prey -- birds that are already increasingly rare. Apparently, there are only so many bugs to eat in Hawaii.

Then, there's the noise.

Hawaiian nights are renown for their gentle lulling calm. Guests at Maui resort hotels infested by coqui now check out of their rooms early because the shrieking frogs make it impossible to sleep.

"It apparently was driving them crazy at the Ritz-Carlton," said Kristy Martin of the Maui Invasive Species Committee. At one point, a hotel was paying bounty hunters $75 a frog, dead or alive.

The coqui's call has been measured at 90 decibels, roughly equal to a lawn mower's racket. The call is so persistent, so urgent, that a Honolulu dentist confessed to Matayoshi that a single frog's night song was making him "nuts."

No state in the nation lies more exposed to the dangers of invasive species than the biologically rich but isolated islands of Hawaii, which have been combating alien plants and animals for more than a century.

Unfortunately, the exceedingly tough challenges facing Hawaii are not unique, and there is increasing concern among scientists that alien invaders in the newly global economies pose an accelerating threat to ecosystems around the world, from the last tracts of tropical forest on Oahu to the corn belts of the Midwest.

The tale of the coqui suggests why.

Researchers suspect that the first frogs arrived on the islands in the early 1990s, hitchhiking on a shipment of nursery plants. The international horticultural trade today represents one of the easiest routes for the spread of invasives. A nice, wet bromeliad may very well have provided the pioneer frogs with a first-class ticket to paradise. The frogs first appeared at seaside luxury hotels.

When Earl Campbell, the invasive species coordinator for the U.S. Fish and Wildlife Service, surveyed the coqui populations on Hawaii in 1998, he and his colleagues could document 10 sites infested by frogs. Now? Campbell reports there are at least 260 known coqui sites on the Big Island of Hawaii alone; more than 40 sites on Maui; 20 on Oahu; and at least two on Kauai.

Campbell suspects the frogs are moving around with the help of humans, in loads of plants and perhaps intentionally. "When it's one or two frogs, the sound can be pleasant," he said.

With no natural enemies, the frogs multiply with gusto. At a single site on the Big Island of Hawaii, Lava Tree State Park, the population is estimated to exceed 20,000 individuals an acre.

"It is almost undescribable," said Robert Sugawara of the U.S. Department of Agriculture's Hilo Field Station on Hawaii. "They're pretty much out of control."

Everyone agrees that they should have attacked the coqui immediately upon its arrival, before it spread from island to island. But by the time government agencies acquired funding and were ready to act, the plague had begun.

First, the researchers decided to spray the frogs with an overdose of caffeine.

"It's like they have a heart attack," Matayoshi explained, "from like a hundred cups of coffee."

The scene is not pretty. "They freak out," said Matayoshi, the hunter who is not unsympathetic to his prey.

On the relatively rare occasions when he has actually captured some frogs, he declines to squish them, instead placing his captives in a glass jar and then putting them into the freezer back at the laboratory, where they die.

But alas, while the Environmental Protection Agency would grant the Hawaii Department of Agriculture emergency temporary waivers to use caffeine as a pesticide, the EPA required that the infestation sites be monitored before and after application of the super-coffee, which had to be administered by trained, certified pest applicators.

The federal regulations proved too burdensome. Today, three tons of powered caffeine sits in a warehouse on the Big Island, as the Hawaiians contemplate their next move.

The Hawaiian Department of Agriculture states that the single greatest threat to the economy, environment, lifestyle and health of the state comes from harmful invasive species. There is a distinct feeling the place is being overwhelmed. Not a week goes by without a short news items appearing in the back pages of the Honolulu Advertiser alerting the public about escaped iguanas, snake sightings, ant hills, noxious seaweed. The island farms and nurseries are under constant siege from foreign insects responsible for cankers, scales and pox. The unemployed are mobilized as human weed-whackers.

Hawaiians live in constant fear of brown tree snakes, which have decimated the bird populations of Guam, and the imported red fire ant -- two species that would wreak havoc on the ecology, agriculture and tourism economy of the islands. And the almost unmitigated spread of the frogs does not inspire confidence in government's ability to fight back.

"The coqui is a pretty good example of a bad situation," said Frank Howarth, an entomologist who holds a distinguished chair in zoology at the Bishop Museum in Honolulu. "They had a pretty fair chance of eradication, but public agencies are constipated by their own bureaucracies."

Howarth argues that it would have been better, ecologically, tohit a few sites hard. "It is far safer to spray the most dangerous pesticide over a very limited area," he said, "than to wait and spray the safest pesticide over the whole island."

So, what to do now about the coqui? Officials are considering the use of hydrated lime, a soil fertilizer that essentially "dries" the frogs to death. But the EPA has refused to approve its use as a frog killer.

On a smaller scale, of course, there is always hand-hunting, which is how Nilton Matayoshi has spent the last year capturing 40 frogs.

Near the end of his night shift, Matayoshi drove by a Home Depot near downtown Honolulu where he had heard frogs singing before. It did not take too many minutes watching Matayoshi on his hands and knees, stalking a calling male amid the golden pathos plants, to realize that this was not going to be an easy victory.

"Got him!"

Matayoshi ran with his closed fist to the truck, got out his glass jar, thrust his hand inside and opened it.


Behind him, the coqui began to sing again.

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