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Coqui Frogs
Coqui frogs (Eleutherodactylus coqui) are small tree frogs which are native to Puerto Rico. The frogs are popular in Puerto Rico and people even claim to enjoy their nightly chorus.
Sometime in the 1980’s they were imported to the Big Island, probably on nursery stock. They have spread rapidly and are now found on Hawaii, Oahu, Maui and Kauai.
Coqui frogs hatch fully formed directly from eggs (no tadpole stage) so they can survive in a much broader range of habitats than other frogs. They live in foliage or on the ground.
In Puerto Rico, researchers identified 40 frogs in a tract 20 meters square. A similar tract in Hawaii’s Lava Tree State Monument found more than 2,000 frogs. Coquis can live anywhere from sea level to 4,000.’ The Institute for Biological Invasions reports that in the rainforests of Puerto Rico, this species can attain density of more than 20,000 frogs per hectare. In Puerto Rico, the coqui frog will bear 4 to 6 clutches of eggs ranging in size from 16 to 41 eggs each. The frogs mature and can reproduce in about 8 months.
Coqui frogs have voracious appetites and State biologists worry that coquis will overwhelm Hawaii’s delicately balanced ecosystems. Their diet is insects, spiders, snails, smaller frogs and mites, placing them in direct competition with already stressed native birds for food.
A second environmental concern is that mongooses and rats, which are virtually the only potential predators in Hawaii, will also experience population increase. In their native Puerto Rico, coqui frogs are prey for rats, owls, cuckoos, snakes and tarantulas.
The most noticeable problem for people is the mating call of the male frogs. During the evening hours, the male frogs go into the trees and call to the females. A backyard full of frogs can reach 70 to 100dB at a distance of 1.5 feet. Depending upon environmental conditions, the mating season can run year-round. Male frogs can usually be found in trees, but babies and females are more likely to be hidden in leaf litter on the forest floor.
There are many methods of eradicating coqui frogs, but to date there has been limited success. Caffeine, citric acid, hot water and hydrated lime have all proven effective in diminishing populations, but application of these substances has proven problematic. (For example, hydrated lime is corrosive and caffeine is regarded by some as being toxic to other species.)
The emergency exemption authorizing use of caffeine to control frogs expired in September of 2002. The State did not seek to renew the exemption because of the cost and restrictions on use of caffeine. Hand capturing has not been very effective as they can be hard to locate and the babies are about the size of a grain of rice.
Pyrenone was also tested on eggs. Nearly 92% hatched as compared with 97% for untreated eggs. Further tests are planned, but it does not look promising. A solution of 16% citric acid was 97% effective in decreasing viability of eggs (CTAHR), especially when the solution was not washed off.Hot water at various temperatures for various lengths of time has also been used. Ranges from 113° for 3 minutes to 115° for ten minutes have experienced some success. (CTAHR)
Hydrated lime is one of the most promising resources. The lime actually benefits the acid soils of Hawaii and is not difficult to apply.
A lot of research is being done in an effort to resolve the frog problem.
The T-STAR Hawaii Coqui Frog Invasive Species Project is investigating the efficacy of vapor heat. Results have indicated that treatment with hot (113°) water at 90% relative humidity for 15 minutes is lethal to frogs and eggs.
T-STAR is also studying a chytrid fungus that causes a lethal disease in amphibians. More information must be gathered on possible unwanted effects of such a treatment. Gene therapy is being used in other places to eradicate cane toads (ironically, brought in from Hawaii). Gene therapy could be used to cause the frogs to produce only male offspring. Sprays are being developed which could cause the frog to become sterile.
Tradewinds is working with local officials to develop the most effective preventative program possible. It currently appears that a wash or steam treatment of some sort at the timber harvesting site followed by a secondary treatment at the mill will be the best solution.
If you have experience with coqui frogs, we are interested in hearing about your efforts and results towards solvingthis problem.
More information and resources can be found below:
Hawaii State Department of Agriculture
Hawaiian Ecosystems at Risk (HEAR)
www.hear.orgCollege of Tropical Agriculture and Human Resources (CTAHR)
University of Hawaii at Manoa
A. Hara, W. J. Mautz, E. M Kilgore
www.ctahr.hawaii.eduThe Institute for Biological Invasions
Todd Campbell
lizardman@utk.edu
http://invasions.bio.utk.edu/invaders/coqui.htmlDepartment of Plant & Environmental Protection Sciences
UH-CTAHR
Beaumont Agricultural Research Center
875 Komohana Street
Hilo, HI 96720
808 981-5194Hawaii DLNR Division of Forestry & Wildlife
Fred Kraus
1151 Punchbowl Street, Room 325
Honolulu, HI 96813
808 587-0614
fkraus@hawaii.eduPlease report any known coqui frog locations to:
- Hawaii Department of Agriculture Pest Hotline (808) 643-7378
- Big Island Invasive Species Committee (808) 961-8065
- Department of Agriculture Invasive Species (808) 933-3346
Noise & Sound | Traffic |Clean Air & Water | Coqui Frogs | Plantation Forestry | Biomass Energy Advantages | Eucalyptus & The Environment