Mike Shiroma’s neighborhood in the Pālolo Valley sounds different than it did when he was a kid, all because of the invasive coqui frog.
The quarter-sized tree frog native to Puerto Rico calls from dusk to dawn. They are one of the loudest frogs in the world, with calls reaching up to 100 decibels, similar to a lawnmower or motorcycle. They hitchhiked to Hawaiʻi Island in 1988 and have since set up colonies on Oʻahu in Pālolo Valley, Waimānalo and the Kuliʻouʻou summit.
Shiroma said he’s witnessed the number of frogs grow from a handful to dozens to thousands, and now estimates that there are 15,000-20,000 coqui frogs in Pālolo Valley.
Shiroma described the coqui frog noise as a “permanent, audio graffiti.”
“They're changing the environment forever,” he said.
Sidney Lynch called the noise deafening. She noticed the occassional frog washing down the Waiʻōmaʻo Stream and would call the Department of Agriculture to catch it. She offered to help after she noticed more and more frogs washing down the stream in 2025.
She co-founded Pālolo Coqui, a group of volunteers that meets multiple times a week to catch and kill coqui in the Pālolo Valley. Volunteers have caught 6,085 since they started in March.
“Even though it’s only concentrated in a five street area, it’s getting much noisier and they can spread,” Lynch said. “At this point, if there’s the chance to eradicate them, we may as well try.”
When volunteers came to Shiroma’s door with a flyer earlier this year, they joined forces to fight the invasion, going from what Shiroma called an “army of one” to a team. Shiroma has been hunting coqui frogs for years, and said he’s getting burned out and discouraged.
Volunteers wear long-sleeve neon shirts, long pants, headlamps and sturdy shoes, and carry plastic tubes, UV flashlights, citric acid solution and radios, and head out into the protected state land bordering the neighborhood to search for frogs.
Here’s how it works: Volunteers listen for the distinct “ko-KEE” call, approach the frog and place a long plastic tube on the frog. The frog jumps up and into the tube, and volunteers put the frog into a small bottle full of a citric acid solution where it is killed.
The male frogs like to hang out on logs and smooth leaves, such as monstera, pothos and heliconia. The “ko” of the coqui’s call asserts their territory and the “kee” calls for females.
Shiroma read scientific papers that said certain amphibians floresce under UV light. He tried it out, and found that certain UV light makes the coqui appear black and their eyes glow, allowing volunteers to look for frogs with UV flashlights when they are not calling.
“To me, this is the game changer. There’s no better discovery than this,” Shiroma said.
The coqui frog is one of 15 high priority pests that the Oʻahu Invasive Species Committee is monitoring. OISC is a project under the University of Hawaiʻi Pacific Cooperative Studies Unit that coordinates between communities, the Department of Agriculture and Biosecurity and the Department of Land and Natural Resources. OISC first got involved with coqui frogs in Pālolo Valley in September 2024.
Robbie Snyder, a community engagement liaison with OISC, detailed the negative impacts coqui frogs can have on Hawaiʻi.
Coqui frogs have no natural predators on Hawaiʻi, so they get more dense than they would in their home country. Snyder said that one acre of land on Oʻahu can be home to 36,000 coqui.
The noise changes the soundscape of Oʻahu’s forests, Snyder said. Lynch said that the noise impacts resident’s quality of life.
Homeowners are required to disclose if there’s a coqui frog infestation on or near their property, which can drive down home prices.
Coqui frogs eat invertebrates, which damages Oʻahu’s native plants and can harm native plants when those plants aren’t being pollinated.
“Those insects also play vital pollinating services to our native plants, so when the frogs eat the native insects, we then lose things that can pollinate our native plants, and that has a cascading affect through the ecosystem,” Snyder said.
If snakes were introduced in Hawaiʻi, coqui frogs would provide a “massive food source” and aid their spread.
According to Snyder, the current goal is to contain coqui frogs until the state has the resources or better tools to eradicate them.
“With the resources we have right now, site level eradication of coqui is not possible,” Snyder said. “There isn’t enough funding, there’s not enough people, there’s not enough resources, and that’s even with the incredible community volunteers that we have, but we need more and we need a years-long commitment to funding.”
Snyder said that hand capture alone isn’t enough at this point to eradicate an infestation.
“There are small enough local populations that they haven’t become widespread. Hope is not lost with coqui frogs,” Snyder said.
OISC and state agencies spray a liquid combination of citric acid and water in an attempt to contain coqui frogs. Citric acid, which is found in citrus, some soft drinks and some candies, poses little risk to people and the environment, but is lethal to amphibians because they respirate through their skin.
OISC has been spraying 400 gallons of citric acid month in the Pālolo Valley for about two years and increased to spray twice monthly starting in August.
When coqui frogs infested Wahiawā in 2003, the Hawaiʻi Department of Agriculture and Biodiversity, the Oʻahu Army Natural Resources Program, the Department of Land and Natural Resources and OISC teamed up and eradicated the coqui infestation with a mix of citric spray and hand captures by 2007.
The volunteers in Pālolo have mixed opinions about the use of citric acid spray. Lynch believes citric acid spray is an effective tool and Shiroma believes it’s not as effective as hand capturing the frogs.
Shiroma called it an “agency failure” that the Department of Agriculture hasn’t dedicated more resources to preventing the spread of coqui.
“You guys are using the same broken playbook that’s not working and hasn’t worked for decades. This is not a new problem.” Shiroma. He advocated for the Department of Agriculture to make a dedicated team that works at night.
While the coqui frogs keep calling, Pālolo Valley neighbors will continue donning neon shirts and heading into the forest to stop them.
Haley Lehman can be reached at haley@alohastatedaily.com.
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