Hawaii faces a significant challenge from introduced frog species. The islands have no native frogs; all amphibians present arrived through human activity. These non-native frogs establish large populations, leading to considerable ecological and societal concerns.
Frogs Found in Hawaii
Several frog species have been introduced to Hawaii, notably the coqui frog (Eleutherodactylus coqui) and the Cuban tree frog (Osteopilus septentrionalis). The coqui frog, native to Puerto Rico, arrived accidentally around 1988, primarily as hitchhikers in imported nursery plants and cargo. This small, nocturnal tree frog measures 1 to 2 inches, exhibiting colors from tan to dark brown with distinctive toe pads. Its presence is now widespread on the Big Island, Maui, Oahu, and Kauai.
The Cuban tree frog, native to Cuba, the Bahamas, and the Cayman Islands, is another introduced species found on Oahu. This larger tree frog, ranging from 2 to 5.5 inches, likely arrived via accidental cargo transport or intentional pet releases. While its establishment across all islands is debated, its presence on Oahu is recognized. These introduced species lack natural predators in Hawaii, allowing their populations to expand rapidly.
Impacts on the Ecosystem and People
Introduced frogs, particularly the coqui frog, profoundly impact Hawaii’s natural ecosystems. Coqui frog populations can reach densities as high as 91,000 frogs per hectare, significantly exceeding densities in their native Puerto Rico. These dense populations consume vast quantities of insects and invertebrates, competing with native insectivorous birds and disrupting food webs. Such predation poses a risk to Hawaii’s unique insect and spider species, many of which are already vulnerable.
The Cuban tree frog also presents ecological concerns, preying on native frogs, lizards, and various invertebrates. Its tadpoles compete with native amphibian larvae, potentially reducing their growth and survival rates. Beyond ecological disruption, coqui frogs create significant societal problems due to their loud, incessant calls, which can reach up to 95 decibels. This noise pollution, exceeding Hawaii’s state health standard of 70 dBA, causes sleep loss for residents and tourists, affecting quality of life.
The presence of coqui frogs has also led to economic consequences, including decreased property values in affected areas. The floriculture and nursery industries face challenges, as these frogs can hinder plant sales and exports. Cuban tree frogs can also cause power outages by short-circuiting electrical equipment and secrete a toxic mucus that can irritate human skin and eyes.
Control and Prevention Efforts
Controlling invasive frog populations in Hawaii involves various strategies, tailored to each species. For coqui frogs, citric acid spray is the only product labeled for control in Hawaii, effectively targeting eggs, juveniles, and adults by affecting their skin. This treatment is applied to infested vegetation, though it can harm sensitive plants. Other control measures include hot water or steam treatments for plant shipments, manual removal, and habitat modification like clearing dense vegetation and removing green waste.
Lure traps can also be used to capture coqui frogs. While eradication has been successful in some isolated areas on Oahu and Kauai, it remains a challenge on islands with widespread infestations like the Big Island and Maui. Prevention is crucial, relying on strict biosecurity measures at ports and nurseries to inspect incoming plants, cargo, and vehicles for frogs. Public awareness campaigns encourage residents to report new sightings or listen for calls, aiding early detection and containment.