Date of this Version
Outlooks on Pest Management (August 2012); DOI: 10.1564/23aug05
During the last 25 years, two species of Eleutherodactylus frogs, coqui and greenhouse frogs, have become established in Hawaii and other Pacific Islands. Coqui frogs, Eleutherodactylus coqui, were introduced to Hawaii prior to 1988 via the horticultural trade (Kraus & Campbell 2002). Since their introduction, the number and size of coqui frog infestations have rapidly increased and frogs have spread throughout the four main Hawaiian Islands with the largest infestation on the island of Hawaii. Coqui frogs are small (<65 mm in length) nocturnal tree frogs that are endemic to the island Puerto Rico (Beard et al. 2008). They are completely terrestrial and do not need open water for development because the frogs develop directly from eggs into small froglets. The most distinctive feature of coqui frogs are their loud two-note mating call, “ko-kee” and the call from a single male may exceed 85 db at 0.5 m (Beard & Pitt 2005). In Hawaii, coqui frogs have few predators, few competitors, abundant food resources and ideal climatic conditions. Populations of frogs are abundant in Hawaii with population densities exceeding 90,000 frogs per ha (Beard et al. 2008).
As a result of the extremely dense frog populations and the loud mating call, coqui frogs have affected Hawaii’s environment, economy, and human health. In areas with high frog densities, frogs may consume 690,000 invertebrates/ha/night, reduce invertebrate diversity, and may impact native invertebrate species (Beard 2007; Choi & Beard 2012). Indirectly, the large coqui populations may also alter nutrient cycling and plant herbivory, which could affect the native plants and the invasion of non-native plants (Sin et al. 2008). Coqui frogs may also compete with native species, provide food for invasive predators, or facilitate the establishment of other invasive species, such as the brown tree snake (Boiga irregularis). Due to the loud mating calls and dense populations, many people do not wish to reside in areas with coqui frogs because they disturb their sleep and night time tranquillity. This noise disturbance has led to decreases in property values of land occupied by coqui frogs (Kaiser & Burnett 2006). Moreover, the reluctance of people to risk purchasing products infested with frogs or frog eggs has led to many impacts on the floriculture industry. Plant growers have experienced decreased sales, increased quarantine procedures, destruction of plant shipments, and increased pest control costs (see Beard et al. 2009 for a review). These increased costs have forced several plant producers to move or go out of business.