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Coqui Frogs

The coqui frog (Eleutherodactylus coqui) was probably introduced into Hawaii between 1988-1995 in imported plant shipments from Puerto Rico (Kraus et al. 1999). Sizeable populations are now found on the islands of Hawaii, Maui, Oahu, and Kauai. The frog now threatens Hawaii's multi-million dollar floriculture, nursery, real estate, and tourist industries, as well as its unique ecological systems (Beard and Pitt 2005). Effects from the coqui are predominantly associated with the frog's piercing call and the extremely high population densities that have exceeded 50,000 individuals per hectare in Hawaii. Beyond the noise nuisance, the loud nighttime choruses of male frogs has affected real estate values, as people desire coqui-free property (A. Hara, University of Hawaii, unpubl. data). The floriculture industry may also be affected through the refusal of export shipments, reduced sales, and increased costs associated with control and quarantine efforts. Further, the frogs may affect native insect populations, forest nutrients, compete with native birds and bats, and alter ecosystem processes (Beard and Pitt 2005).

Few options exist for control of wild populations. Mechanical controls include hand capturing, habitat alteration, and trapping. All have limited effectiveness because of logistical problems. Some success has been documented using hot water treatments for quarantine efforts in ornamental plant shipments (M. Wilkinson, pers. comm.). Disease organisms have a low potential for controlling coqui frogs in Hawaii, primarily because viruses and diseases are most effective when applied to small populations of species with low reproductive capacity. In large populations, diseases may induce temporary population declines, but surviving individuals may develop resistance, resulting in population levels similar to those pre-treatment.

Although many frogs are quite susceptible to a variety of chemicals, the terrestrial coqui frog has been unaffected by a wide range of potential pesticides. Currently, only citric acid and hydrated lime have proven to be effective and registered for use to combat the frogs (Pitt and Sin 2004a, Pitt and Doratt 2005). Although these chemicals are effective if sprayed directly on the frogs, there are limitations with these products, including varying efficacy affected by weather conditions, potential toxicity to plants, high costs associated with repetitive spraying of large areas, access to remote or private land, and other factors (Pitt and Sin 2004b).

Summary above taken from:

PITT, W., D. VICE, AND M. PITZLER. 2005. Challenges of invasive reptiles and amphibians. Proceedings of the Wildlife Damage Management Conference 11:112-119.

Literature Cited

BEARD, K. H., AND W. C. PITT. 2005. Potential consequences of the coqui frog invasion in Hawaii. Diversity and Distributions 11:427-433

KRAUS F., AND E. W. CAMPBELL. 2002. Human-mediated escalation of a formerly eradicable problem: The invasion of Caribbean frogs in the Hawaiian Islands. Biological Invasions 4:327-332.

KRAUS, F., AND E. W. CAMPBELL, A. ALLISON, AND T. PRATT. 1999. Eleutherodactylus frog introductions to Hawaii. Herpetological Review 30:21-25.

PITT, W.C., AND R. E. DORATT. 2005. Efficacy of hydrated lime on Eleutherodactylus coqui and an operational field-application assessment on the effects on non-target invertebrate organisms. USDA, APHIS, WS, National Wildlife Research Center, Internal report. Hilo, HI, USA.

PITT, W. C., AND H. SIN. 2004a. Dermal toxicity of citric acid based pesticides to introduced Eleutherodactylus frogs in Hawaii. USDA, APHIS, WS, National Wildlife Research Center. Report to Hawaii Department of Agriculture. Hilo, HI, USA.

PITT, W. C., AND H. SIN. 2004b. Testing citric acid use on plants. Landscape Hawaii July/August 5/12.

More coqui frog photos (Rogelio Doratt, USDA/APHIS/WS Hilo, HI)