Coqui Frogs Are Coming to Oahu

Shrieking, invasive, miniature frogs have overrun the Big Island. Now they want Oahu.


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The “coqui cooker” kills frogs hiding in nursery shipments leaving the Big Island.

Their populations grow exponentially. In the most densely infested parts of the Big Island, the number of coquis can exceed 10,000 per acre.

Odd as it may seem to anybody in Hawaii who has ever been driven into the yard in the middle of the night to squelch a chirping frog outside the bedroom window, the coqui is actually beloved in its native homeland, Puerto Rico. It’s the national amphibian there, a symbol of Puerto Rican pride, celebrated in myth, song and souvenirs.

People aren’t the only ones in who appreciate coquis in Puerto Rico. Snakes, tarantulas, giant spider crabs and a host of other predators not found in Hawaii like them, too. These predators keep coqui numbers in check, and distinguish Puerto Rico’s loveable, limited coquis from East Hawaii’s uncurbed infestation. (In Hawaii, chickens, mongoose, rats and even cats have been known to eat coquis, but nothing is eating the frogs fast enough to make a difference.)

When heard from a distance, a chorus of coqui frogs has a melodious quality. When 10,000 coquis drown out normal human speech, even a Puerto Rican might complain.

Researchers have been looking for ways to control coquis since the late 1990s. Hydrated lime was used for a while, but ran afoul of federal pesticide regulations, as did caffeine spray, which gave the frogs heart attacks (and gave coffee lovers pause). Chytrid fungus, a natural pathogen that has been decimating other amphibians all over the world, turned out to be harmless to coquis. Pesticides, parasites, soaps, surfactants, Tylenol and nicotine have all come up short as coqui-control agents. Recent research at UH-Hilo has found that Prozac suppresses coqui libido and aggression, leaving the frog no reason to chirp. But how 10,000 frogs might be put on an antidepressant has yet to be worked out.

“It’s just a hot shower,” says inventor Arnold Hara, seen here, inspecting the cooker’s water tank.

University of Hawaii entomologist Arnold Hara has proposed sterilizing massive numbers of male coquis through irradiation, then releasing them into the wild, a population-control technique that been used successfully on insects such as the Zanzibar tsetse fly. He’s yet to find funding for the research.

Hara has been looking for ways to stop the spread of coquis frogs for more than a decade. He’s come up with some wild ideas, such as dumping high volumes of seawater onto coqui-infested habitat, burning down the habitat altogether, and praying for either a severe drought or a freeze to strike Hilo. He’s also discovered that water heated to 113 degrees and sprayed on infested plants for five minutes kills both coquis and their eggs. “It’s just a hot shower,” he says. “That’s all they need.”

Big Island nurseries now use Hara’s “coqui cooker”—a shipping container transformed into a plant shower—to treat shipments of plants before sending them off-Island. The state Department of Agriculture has built its own cooker to treat contaminated material it finds at Honolulu Harbor.

Although Hara concedes that the coqui is in Hawaii to stay, ultimately, he believes, with or without help from science, nature will knock its population down to more tolerable levels. “Eventually, there’s going to be a disease, or a parasite, or some other controlling biological factor,” he says.

When that might happen is anybody’s guess. Presuming it does happen, and once everyone who grew up in Hawaii in the pre-coqui era is replaced by a new generation that never knew the quiet of a Hawaiian night, then perhaps our coqui problem will be a thing of the past.

In the meantime, Oahu, brace yourself.

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Coqui Sounds: Courtesy Hawaii Ecosystems at Risk Project

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Honolulu Magazine November 2018
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