Coqui study
UHH researchers to probe effects on native fauna

Thursday, March 10, 2005 8:54 AM HST

By DAVE SMITH
Tribune-Herald staff writer

Although known best for its nocturnal shrieking, the coqui frog is also considered a threat to Hawaii's fragile ecosystem.

Two University of Hawaii at Hilo researchers are preparing to investigate just how much of a danger the invasive tree frog poses to Hawaii's unique fauna.

UH-Hilo biology professors William Mautz and Rebecca Ostertag are part of a team that has received a $300,000 grant from the National Science Foundation to investigate the coqui's effect on Hawaii's forests.

Along with Flint Hughes of the U.S. Forest Service and Paul Klawinski of William Jewell College in Missouri, the UH-Hilo biologists will carry out a three-year study of the frogs' impact on two types of forests in Hawaii.

Mautz said the research will focus on stands of native ohia trees as well as forests of albizia, a fast-growing alien tree species. He said the latter species was chosen because of the large number of the nickle-sized coqui sometimes associated with it.

" It appears that the coqui frogs do particularly well in the albizia forest," he said.

Until last year, they certainly did in an albizia forest several miles from Pahoa. Tall albizia trees dominate Lava Tree State Monument and prior to a concentrated eradication effort, the park had the dubious distinction of having the highest known concentration of coqui on the Big Island.

Coqui frogs, natives of Puerto Rico believed to have arrived in Hawaii about a dozen years ago in potted plants or nursery materials, are prodigious eaters of insects. Scientists are concerned that they will upset the delicate balance of Hawaii's ecosystems by eating native and other insects that provide food for native birds.

"We expect a major alteration of the food web -- who eats who in the forest," Mautz said. "(Coqui) have become one of the major predators in the forest even though they're quite small."

He said such a disruption could have a variety of effects, including some directly affecting humans. If the coqui's diet includes a large number of spiders, for instance, that could result in an increase in their prey, such as mosquitoes.

Mautz said research has shown that mosquitoes are almost never part of the coqui diet because the two seldom meet.

He said preliminary research has shown lower densities of coqui in ohia forests. But those forests also are more susceptible to change as they lack many of the singing insects found elsewhere.

" Here in Hawaii the forest is really quiet," he said.

Mautz and other scientists are also concerned that the coqui population would represent an ample food source for the brown tree snake if the reptile plaguing Guam ever becomes established here.

Mautz said since the National Science Foundation provided only half the money requested, the research team is hoping to receive additional funding from the state.

Those funds, along with a research proposal from University of Hawaii researcher Arnold Hara to study the frog in its native habitat, are part of a request to the Legislature from Mayor Harry Kim.

The frog's impact on Hawaii, which includes threats to agricultural exports to other islands and untold disruptions of sleep for tourists and isle residents, prompted Kim to declare a state of emergency last year.

This year the mayor asked state lawmakers for $2 million annually to battle the coqui. Kim said Wednesday that he remains hopeful that the Legislature will support his plan that features public education, research and eradication efforts.

" I'm keeping my fingers crossed," he said. "This is a huge problem and it's going to require a comprehensive approach."

Dave Smith can be reached at dsmith@hawaiitribune-herald.com.

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