HISC enews issue 24
Controlling coqui frogs in Hawai‘i continues to be an interagency effort involving the Coqui Frog Working Group, including Hawaii Department of Agriculture, Counties, community members, private land-owners, Invasive Species Committees, and USDA Wildlife Services. These efforts have largely focused on using habitat modification and spraying with hydrated lime or citric acid. Monitoring efforts on the Big Island now reveal massive areas of infestation and island-wide control or eradication is out of reach of any reasonably available resources or technology. Only limited control in priority sites will be feasible.
Our efforts on the other main islands have been geared toward preventing establishment, and have been successful. On O‘ahu and Kaua‘i we have nearly eliminated the known populations of coqui there and work to prevent re-introductions from high-risk pathways, especially plant importation from Big Island nurseries. On Maui we have one large infestation. With a dedicated effort, coqui on Maui should be eradicable.
Our labors are best directed to prevent the spread of coqui. All exports, especially plants, from the Big Island must be inspected and sanitized to prevent coqui from re-infesting places where they have been largely eradicated.
MISC has been working with nurseries on Maui to certify them "coqui free". This helps consumers find plants that are less likely to be infested. By focusing our efforts on prevention, and eradication of populations that are feasible, our invasive species work should be effective, even with reduced funding.
Invasive Species Coordinator
In Big Island roadside surveys crews listen for frog calls within approximately 100 yards from the road in any direction. Few populations were found above the 2,500 feet elevation. Controlling areas that reach or exceed this elevation should be a priority.
9 March 2009
Coqui still a priority
The coqui frog (Eleutherodactylus coqui), a tiny amphibian accidentally introduced through the nursery trade from the Caribbean in the late 1980s, continues to plague island communities, nurseries, resorts, parks and forests. Its most distinctive feature is the male’s nocturnal two-note mating call, whose volume can rise to an unpleasant 80 decibels. The coqui also impacts the biodiversity of Hawai‘i’s native ecosystems, especially forest insects, including endangered species and nutrient cycling in forests.
There are small infestations of coqui on O‘ahu, Kaua‘i and Maui where Invasive Species Committees have worked to keep the numbers in check. No coqui frogs infest Moloka‘i at present. They are out of control on the Big Island.
The O‘ahu coqui frog working group, a collaboration of the Invasive Species Committee, DLNR’s Division of Forestry and Wildlife, Hawai‘i Department of Agriculture, and the O‘ahu Army Natural Resources Program, worked to systematically control the frogs through habitat modification and spraying with citric acid. Efforts have resulted in the eradication of a naturalized coqui frog infestation in Wahiaw?.
According to Rachel Neville, O‘ahu Invasive Species Committee manager, four requirements were met to eradicate coqui: 1) permission to enter private property where the frogs were located, 2) an approved control method, 3) funding to start work before the frog population became too large, and 4) continued funding to complete the project.
The Kaua‘i Invasive Species Committee has controlled an infestation of coqui frogs on 22 acres in Lawai. Workers there continue to eliminate the last few calling frogs.
The Maui Invasive Species Committee experienced a setback on progress made controlling the coqui last year when control efforts suffered funding cuts. As a result, the only remaining coqui infestation in Maliko Gulch spread from 127 to 216 acres. Further cuts will mean substantial growth in infested area and population densities, allowing the coqui population to grow and probably spread into other communities.
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A huge problem on the Big Island
On the Big Island more than 60,000 acres are infested with coqui frog, mostly in Puna and Hilo areas. Total eradication is not possible with current technology, although control efforts continue to focus on residential communities and natural areas that promote biodiversity.
Ray McGuire, HISC’s Coqui Program coordinator, heads up Big Island roadside surveys to listen for frog calls within approximately 100 yards from the road in any direction.
Surveys showed that at least 60,000 acres are infested, not including unsurveyed areas like forest reserves. He estimates that spraying this area once would cost $205 million, including the cost of the chemical and manpower. Control would require two or three applications, McGuire said.
“I would assume the figure will be even higher than this estimate because there are areas of infestations that are hard to reach by sprayer and so it may be necessary to access these areas by helicopter,” McGuire said. “To successfully eradicate an area takes multiple sprays depending on the terrain. A site is not considered eradicated until a year has passed without signs of coqui.”
Prevention of movement of frogs to locations on the Big Island or interisland is considered to be more cost-effective use of limited resources.
Many conservation programs in Hawai‘i receive Natural Area Reserve Fund support. Cutbacks would also inhibit response to reports of new infestations of coqui and other invasive species.
All Invasive Species Committees throughout the islands face probable program shutdowns. Resource managers and ISC coordinators and staff say continued funding and monitoring are essential to prevent another large infestation.