O'ahu fights frog invasion
By Timothy Hurley
Advertiser Staff Writer
They're loud. They're noisy. And they could be moving into your neighborhood soon.
They're Caribbean frogs, capable of reproducing at amazing rates and creating a chorus of mating calls with ear-splitting potential.
Volunteers organized by the O'ahu Invasive Species Committee have been going out into the field weekly to capture the frogs at night.
The goal is to control a problem before it reaches the proportions of the Big Island, where the infestation has exploded to more than 150 locations from about eight only three years ago.
At least one Big Island site is reported to be infested with thousands of frogs, raising their voices to what has been described as deafening levels.
There are only two known infestations in the wilds of O'ahu and seven more areas with unconfirmed reports of the frogs, according to Nilton Matayoshi of the state Department of Agriculture's Plant Pest Control Branch.
At Wahiawa, about 60 frogs have been picked up by hand by the volunteers at night, when the males let out their cries. At Punalu'u, less than 20 frogs have been found, said Leila Gibson U.S. Fish & Wildlife Service biologist.
The largest O'ahu infestation appears to be at Wahiawa. Residents, who reported the infestation there in May, reported hearing them for at least a year, Gibson said.
Capturing the creatures by hand is an adequate control measure for now, but officials are awaiting EPA permission to use a new caffeine compound that has been proven to kill them. Eradication may be within reach on O'ahu with this new treatment, which could be approved within a couple of months, Matayoshi said.
State researchers have also developed a process that uses hot water to help control the frogs at nurseries. But there's a question whether the heat process, which drenches plants and their pots in 113-degree water for three minutes, is affordable for nurseries.
In their native Caribbean islands, the frogs, Eleutherodactylus coqui, live in populations of up to 8,000 an acre. Females can produce more than 200 eggs a year, with each frog reaching sexual maturity in just eight months. The coqui's cousin, Eleutherodactylus planirostris, or greenhouse frog, is about half the size at 1.5 inches and isn't quite as loud.
Both of these frogs arrived in the Hawai'i in recent years in plants imported from the Caribbean, and they likely are being spread as hitchhikers in nursery materials.
For the past few months, O'ahu agriculture officials have been responding to reports from those who believe they've heard the frog as well as investigating potential new sources at nurseries.
Frogs have been discovered in at least four retail nursery locations on O'ahu, Gibson said.
One woman from 'Ewa Beach bought a plant from Home Depot store nursery and later found a frog in it.
If you hear or see them, report it to the Department of Agriculture 24-hour hotline at 973-9542.