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Observations of the Coqui Frog, Eleutherodactylus coqui, in Puerto Rico


     Researchers from Hawai`i visited Puerto Rico in January, August, and December 2006 to gain insight about the coqui frog in its native habitat.  Research focused on factors affecting populations, parasites of the coqui frog, noise levels generated by the frogs, and understanding how people cope with the noise. 


     Frog populations in Puerto Rico were observed to be numerous and dense in a variety of habitat types in different locations around the island.  Vegetation was very similar to that of east Hawaii, with forest understory being dominated by broad leaved bromeliads, vines, grasses, and ferns (Fig. 1 & 2).  One major and noteworthy difference was the lack of rocky crevices or a’a lava used by coqui frogs in Hawai`i for nesting and protection (Fig. 3).  

Figure 1. Typical forest habitat and vegetation in Puerto Rico.



Figure 2.  Rocky substrates, such as a`a lava present in Hawai`i, but absent in Puerto Rico, provide shelter and nesting habitat for coqui frogs.

     In January, estimated population density in Puerto Rico was roughly half that of populations in Hawai`i (Fig. 3) .  In August and December, SPL measurements approached those recorded in Hawai‘i, ranging from 50-73 dB, indicating that populations were nearly equal (Fig. 4).  This difference was likely due to decreased frog activity levels during the cooler winter months.  Eleutherodactylus coqui was the dominant species, with other frog species and insects heard in the background.


     Thorough dissections of 80 frogs collected from four different locations recovered at least seven different parasite species.  Of these, two may be potentially pathogenic to coqui frogs.  Further research and testing is necessary to determine if one or both parasite species: 1) can successfully be cultured in the lab; 2) have enough of a pathogenic effect on coqui frogs to warrant consideration for biological control; and 3) are host-specific so as to not harm native Hawaiian animals.


     In Puerto Rico, most residents do not appear bothered by the coqui frogs calling, and revere them as part of their culture.  Background noise levels of other frogs and insects calling were noted in areas where coqui frogs were numerous.  While recorded sound levels were as high as those in Hawaii, competition between frog species may result in fewer coqui frogs calling in an area, resulting perhaps in the coqui sounding less annoying and more melodious in Puerto Rico.


     Professional relationships with scientists in Puerto Rico were established to facilitate research efforts and share information.  Being an important part of the culture and native ecosystem, research on coqui frogs in Puerto Rico has primarily been focused on population distribution and abundance, natural history, and ecology rather than on control.  In Hawai`i however, any potential new management strategies for coqui frogs are contingent upon further research to identify factors regulating population size and distribution.


Photo by S. Marr, UH–CTAHR


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