Noisy nuisance
Coqui frogs threaten more than the peace.
Patricia Tummons
July 2, 2003 Honolulu Weekly
The scene: Hilo High School auditorium. The date: an evening in early May. The occasion: After months of rehearsals, students from Hilo and Waiäkea high schools perform their hearts out in Jekyll and Hyde: The Musical.
Throughout the performance, an unscripted chorus accompanies the dialogue and drowns out all but the most robust vocalists and ensemble numbers. It is the sound of the coqui, a tiny native frog of Puerto Rico that has been invading more and more neighborhoods on the island of Hawai‘i. Thousands of the frogs inhabit the brush behind Hilo High, and their noise fills the night air, disrupting evening classes as well as the occasional student play.
Across the islands, such scenes are occurring with increasing frequency. From Hawai‘i to Kaua‘i, tiny but populous frog cities are popping up, unseen to all but the most vigilant, but audible to nearly everyone. Initially, the soft sounds of the evening and night are pierced by the distinctive two-tone chirp of one or two males of the species Eleutherodactylus coqui (the females are silent). Within a few weeks or months, the numbers of frogs have multiplied and the occasional chirp has grown into the amphibian equivalent of Van Halen.
As much as the noise of the coqui is a nuisance in populated areas, some researchers think its presence on the islands poses a potential environmental nightmare of even greater dimensions. Bill Mautz, assistant professor of biology at the University of Hawai‘i at Hilo, noted that in Hawai‘i, where the frog has no natural enemies, the coqui can achieve densities of 15,000 per acre, many times the densities reported in the frog’s native range.
With these high densities, Mautz explained, the coqui and the smaller (and quieter) greenhouse frog (Eleutherodactylus planirostris) “are eating a huge amount of insects and other crawling bugs and spiders in the ecosystem, and so we expect they’re going to change the community of animals in the forest — insects, spiders, other arthropods — in ways that are hard to predict.”
Some researchers have estimated such dense populations of coqui may eat up to 200 pounds of bugs per acre per year. Do they eat mosquitoes, as some champions of the coqui claim?
Only rarely, said Mautz.“Coqui tend to reduce the numbers of spiders. They’re not major mosquito eaters.”
So how is the state dealing with the coqui? It has looked at several control measures. One of the earliest was a hot bath for landscape plants. This approach has obvious limitations, however. It does not work well on areas that are heavily infested or out of reach of a source of warm water.
More controversial was the identification of caffeine as a means of killing the frogs. Although application of a caffeine spray to infested areas received emergency approval (since lapsed) from the Environmental Protection Agency, it was not used owing to concerns over possible water quality impacts. Recently, a 16 percent solution of citric acid has been identified as a “frog-icide.” The acid kills frogs on contact, but, if it is not washed off within an hour of application, sensitive plants can be damaged. Because of this, some nurseries have been reluctant to employ citric acid against coqui infestations.
A fungal disease, chytridiomycosis, that has devastated vulnerable frog populations across the world is a possible biocontrol agent for coqui. Another might be a type of fly that eats coqui eggs in Puerto Rico. The species is already in Hawai‘i, said Arnold Hara of the University of Hawai‘i’s College of Tropical Agriculture and Human Resources, “and may only need some time to begin infesting coqui eggs.”
Kahuku Ranch restoration?
In April, the Board of Land and Natural Resources fined Damon Estate $480,335 for allowing Steve’s Ag Services to take hundreds of trees from Conservation District land owned by the estate in Ka‘ü (Environment, “Koa kleptomaniacs,” HW, 5/7). Believing the fines were miscalculated, Damon Estate’s attorney requested a contested case hearing immediately after the board’s decision.
Now it appears that the estate may avoid paying any fine at all, regardless of the outcome of the contested case. One of the conditions of the April 11 decision allows the estate to restore the degraded land in lieu of paying the fine (although it still must pay more than $13,000 in administrative costs).
This option was at first thought to be infeasible, since Damon Estate was to transfer most of the ranch to the National Park Service in May. As it turns out, though, the estate is trying to achieve restoration by partnering with the Park Service.
And the estate has moved quickly. Within a week of the Land Board’s April decision, Damon Estate consultant Charles Wakida had prepared a reforestation plan, attorney Linnel Nishioka told the Land Board in May. She asked that the Land Board delay selecting a hearing officer while the estate continues to work with the National Park Service on the reforestation plan.
“We don’t object with the process moving forward, but the state can save resources” by not appointing a hearing officer right away, Nishioka said. The Land Board agreed to her request and voted to defer selecting a hearing officer until Aug. 31.