Coqui frogs have been a nighttime nuisance on Hawaiʻi Island since the 1980s, when they were accidentally introduced from Puerto Rico.
Their populations have exploded on the Big Island, and one study found that in the past 14 years, the frogs have gone from occupying 30% of roadside areas to half of them — and the frogs may be moving into higher-elevation habitats, too.
But what makes them so good at being an invasive species? A new paper titled “Fortune may favor the flexible" explores what makes coqui frogs such successful invaders in Hawaiʻi.
Eva Fischer, an assistant professor at the University of California, Davis, spoke with The Conversation about how an invasive species like the coqui manages to thrive outside its native habitats.
Fischer said coqui frogs have unique traits, like skipping the tadpole stage and breeding in lava tubes, that support their successful spreading in environments like Hawaiʻi. Their bold and exploratory behavior also helps.
“We sort of had these two different ideas, which were that if the populations really explode, maybe the guys who move out away and sort of are motivated to leave are the ones who are most bold and exploratory," she said.
"Or maybe they, at the center, start to become really competitive and interact with each other in that way, and so the guys who are moving out are actually the more shy ones, because they're just trying to get away from other frogs.”
After some field tests, Fischer and her team found support for the idea that range-expanding frogs are more exploratory, and their behavior is influenced by both population density and elevation.
“Coqui are just super flexible and able to adapt sort of immediately to what's going on in their environment,” Fischer added. “And that could also be a really key piece of being a good invader.”
This story aired on The Conversation on Aug. 4, 2025. The Conversation airs weekdays at 11 a.m. Hannah Kaʻiulani Coburn adapted this story for the web.
