Help needed in spotting invasive frogs

Keren Gundersen, Project Coordinator for the Kauai Invasive Species Committee, is seeking the public’s help in identifying where coqui frogs and greenhouse frogs are located.

The invasive pests were first spotted in Hawaii in 1992, and Gundersen says the frogs are now a danger to the state’s native ecosystems, agriculture and visitor industry.

The frogs are now established on the Big Island, Maui and Oahu, as well as Kauai. However, only one population of the coqui frog has been confirmed on Kauai.

Gundersen is requesting help from the public in providing coqui and greenhouse frog sighting information. Anyone spotting the frogs should call the United States Department of Agriculture at 246-1432 or 632-0532.

The sighting reports will be checked, and reported to the USDA Animal and Plant Health Inspection Service (APHIS) team who will include the information in a management and control plan.

Many local, state and federal organizations are working to find solutions to the damage that these two non-native frog species are causing, Gundersen says.

Within the next two weeks an APHIS team is scheduled to be on Kauai to conduct research and to comply with the National Environmental Policy Act to develop environmentally sound strategies to manage the coqui and greenhouse frog populations.

Scientists from APHIS Wildlife Services, Kauai Invasive Species Committee, the state Department of Agriculture, and the University of Hawaii’s College of Tropical Agriculture and Human Resources are working cooperatively to conduct the research.

In addition, U.S. Department of Agriculture, Wildlife Services is currently treating areas with citric acid to eliminate greenhouse frogs from resorts located along Poipu Beach.

The male coqui frog, known for its piercing chirp, is much easier to detect than the quieter greenhouse frog. Coqui frogs are about the size of a quarter, and greenhouse frogs are about the size of a dime. Both species are light brown to dark or reddish in color and have variable patterns, including light stripes down the back.

Beginning at dusk and continuing until dawn, male Coqui frogs move into the trees and call “ko-kee” repeatedly to attract females. The noise from a group of frogs can exceed 90 decibels, rivaling the sound of a lawnmower or chainsaw. The greenhouse frog also makes an inconspicuous chirp into the night resembling loud squeaky wheels.

In their native range, Caribbean frogs consume a diet consisting mostly of insects. While this is beneficial in the Caribbean, it could be devastating to Hawaii, which doesn’t have any native amphibian species. The majority of Hawaii’s native forest birds are partially or entirely dependent on insects for food. If coqui and greenhouse frogs spread to forest bird ranges, the frogs could out-compete native, endangered species. The increase in the frogs could also serve to boost the rat population serving as an unlimited food source.

Hawaii’s vital floriculture and nursery industry is also at risk. Grower sales of Hawaii’s flowers and nursery products totaled a record $83.4 million in 2000, a figure that puts Hawaii’s sales behind only Florida and California. An infestation of Caribbean tree frogs could jeopardize local plant sales as well as exports. Several inter-island shipments of nursery products have already been rejected due to Caribbean tree frog infestations.

Control methods for the frogs have included caffeine and citric acid, which have both proven to be effective during tests. While the use of caffeine requires special authorization, citric acid is already on the Environmental Protection Agency’s list of non-regulated, minimum-risk applicants. In addition, hand capturing and habitat modification can also be effective, but only on a small scale. In order to remove large populations of frogs, scientists are looking to citric acid and other natural products that can easily be applied to trees and shrubbery where Caribbean frogs are likely to be found.

Early detection and prevention are unquestionably the most effective ways to tackle aggressive alien invasive species, Gundersen says. Further information may also be found at http://www.aphis.usda.gov/oa/pubs/pa_wscoquitfrogs.html.

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