Coqui Frogs Are Coming to Oahu
Shrieking, invasive, miniature frogs have overrun the Big Island. Now they want Oahu.
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In the wild, coquis grow to about an inch. In UH entomologist Arnold Hara’s laboratory, they can grow much larger.
“The adrenaline when you catch them is unreal,” Minami says. But he’s driven by more than just the thrill of the hunt. He’s well aware of his personal stake in the battle. He lives near a forested area in Aiea Heights, and he’s a light sleeper.
A young female coqui can lay a clutch of eggs every 2.5 weeks, producing more than 1,400 eggs per year. The babies hatch as fully-formed froglets, skipping the tadpole stage.
“Even when the birds start singing, I wake up,” he says. “I don’t want these frogs up there.”
Not all of Oahu’s coqui incursions have been small enough for a few guys with flashlights and plastic bottles to deal with. In Hauula, coquis had spread to several yards and a public park before anyone thought to call the Pest Hotline (residents mistook the chirping frog for an obnoxious, new nocturnal bird). There have been multiple infestations in and around Waimanalo’s plant nurseries.
When an area has more coquis than anybody can catch by hand, it’s doused with citric acid, the only federally-approved chemical for coqui control.
Oahu’s worst coqui outbreak to date occurred in Wahiawa, where, around 2001, the frogs spread from a small backyard nursery across a neighborhood and into a military training area at Schofield Barracks. Workers thinned about five acres of brush on the base and soaked the trees and ground with citric acid pumped through fire hoses. They marched through the neighborhood in chemical suits, spraying citric acid from backpack-mounted tanks. They sprayed every few weeks, for five years, before the frogs were finally silenced and the operation was declared a success, in 2008.
“The crew would work until 10 at night, and the residents were very tolerant of us,” says Rachelle Neville, coordinator of the Oahu Invasive Species Committee. “If they had put up a stink, we might not have succeeded.”
At its height, the Wahiawa infestation included about 150 calling male frogs.
In the laboratory, female coquis can lay some 50 eggs every two to three weeks. Unlike other frogs, the coqui has no tadpole stage. Babies hatch as fully formed froglets, their range unhindered by the need for standing water that tadpoles have. In about eight months, the little hatchlings become breeding adults.
The coqui’s incessant call, repeated every few seconds, explodes from its tiny body at up to 95 decibels. That’s louder than an alarm clock, a barking dog or your average leaf blower. If you had to work with something that loud right next to your head, the Occupational Safety and Health Administration would make you wear hearing protection.
The females aren’t the noise makers. They rasp quietly, unnoticed by anyone but other coquis. It’s the males that make all the racket. Their two-note ko-KEE call is part macho bluster, part love song. The low-note ko is a warning to other males to keep their distance (it also helps them distribute themselves evenly through the foliage). The high-note KEE is the call to reproductive action. Ko-KEE could, therefore, be translated as, “Keep your distance, bruddahs / Ladies, I’m yours.”
Coqui Sounds: Courtesy Hawaii Ecosystems at Risk Project