Neotropical frogs in Hawaii: status and management options for an unusual introduced pest

Two species of neotropical frog, Eleutherodactylus coqui and E. planirostris, have been introduced into the state of Hawaii via the horticulture trade. Since 1997 frog colonies within the state have rapidly spread from accidental and intentional causes, and frog abundance within colonies has grown rapidly. Colonies of these frogs are currently known from 262+ locations on the island of Hawaii, 45+ on Maui, 35+ on Oahu, and 2+ on Kauai. Although these frogs were originally restricted to horticulture sites, they are now found in residential areas, resorts and hotels, and public lands. Within their native range, they may reach densities of 20,000 frogs/ha. Given the current population irruptions of these frogs in Hawaii, similar densities are being reached and exceeded. Due to the high potential biomass of introduced frogs there are realistic anthropogenic (economic and quality of life) and ecological concerns associated with their spread. Since 1998, research has been conducted with the goal of developing control techniques for these frogs. A primary result of this research effort was the determination that a spray application of a 2.0% concentration caffeine and water solution can effectively eliminate local frog populations. The aforementioned research result was used to support a United States Environmental Protection Agency Sec. 18 (Emergency) Registration for the use of a 2% caffeine solution for Eleutherodactylus frog control in the State of Hawaii by the Hawaii Department of Agriculture. Although this tool is available for localized control of frogs, efforts by federal, state, and county agencies to control this pest in Hawaii has been hampered by a lack of funding, unclear legal jurisdiction, and bureaucratic inertia