Coqui Research Articles

Parasite loss and introduced species: a comparison of the parasites of the Puerto Rican tree frog, (Eleutherodactylus coqui), in its native and introduced ranges

The Puerto Rican frog, Eleutherodactylus coqui has invaded Hawaii and reached densities far exceeding those in their native range. One possible explanation for the success of E. coqui in its introduced range is that it lost its co-evolved parasites in the process of the invasion. We compared the parasites of E. coqui in its native versus introduced range. We collected parasite data on 160 individual coqui frogs collected during January-April 2006 from eight populations in Puerto Rico and Hawaii. Puerto Rican coqui frogs had higher species richness of parasites than Hawaiian coqui frogs. Parasite prevalence and intensity were significantly higher in Hawaii, however this was likely a product of the life history of the dominant parasite and its minimal harm to the host. This suggests that the scarcity of parasites may be a factor contributing to the success of Eleutherodactylus coqui in Hawaii.

Economic impacts of E. Coqui frogs in Hawaii

Eleutherodactylus coqui, a small frog native to Puerto Rico, was introduced to Hawaii in the late 1980s, presumably as a hitchhiker on plant material from the Caribbean or Florida. The severity of the frogs' songs has lead to a hypothesis that the presence of the frog on or near a property results in a decline in that property's value. The objective of this study is to measure the damage costs from the coqui's loud mating songs through a hedonic pricing model. We find that the per–transaction reduction in value appears to be about 0.16%, holding constant district, acreage, financial conditions, zoning, and neighbourhood characteristics.

Potential consequences of the coqui frog invasion in Hawaii

ABSTRACTThe Puerto Rican frog, Eleutherodactylus coqui, has invaded Hawaii and has negatively impacted the state's multimillion dollar floriculture, nursery and tourist industries; however, little is known about the ecological consequences of the invasion. Using data from Puerto Rico and Hawaii, the authors summarize the potential consequences of the invasion and describe future research needs. It could be predicted that the coqui would reduce the abundance of Hawaii's endemic invertebrates. However, data suggest that coquis are mostly consuming non‐native invertebrates, and not invertebrate pests, such as mosquitoes and termites. Endemic invertebrates are likely to represent a portion of the coqui diet, but it remains uncertain which endemic invertebrates are most threatened by coqui predation and whether there will be indirect effects that benefit or harm them. It could be predicted that coquis would compete with endemic birds for invertebrate prey, but there is presently little overlap in the habitats used by coquis and endemic birds. Although, coquis may make bird re‐invasion into lowland ecosystems more difficult; alternatively, coquis could serve as an additional food source for some endemic birds. Finally, it could be predicted that coquis serve as a food source for endemic‐bird predators, such as rats and mongoose, and bolster their abundance. Preliminary data suggest that coquis will not bolster rat or mongoose populations. Managing coqui populations in Hawaii has been a challenge. A population has not yet been eradicated using citric acid, the only federally approved pesticide for coquis. It is unlikely that coquis will ever be eradicated from the islands of Hawaii and Maui, where there are now hundreds of populations. Quick and severe responses to new introductions may be the only effective means of containing the spread of the coqui.

In vitro fertilization and artificial activation of eggs of the direct-developing anuran Eleutherodactylus coqui

Although much is known about the reproductive biology of pond-breeding frogs, there is comparatively little information about terrestrial-breeding anurans, a highly successful and diverse group. This study investigates the activation and in vitro fertilization of eggs of the Puerto Rican coqui frog obtained by hormonally induced ovulation. We report that spontaneous activation occurs in 34% of eggs, probably in response to mechanical stress during oviposition. Artificial activation, as evidenced by the slow block to polyspermy and the onset of zygote division, was elicited both by mechanical stimulation and calcium ionophore exposure in 64% and 83% of the cases, respectively. Finally, one in vitro fertilization protocol showed a 27% success rate, despite the fact that about one third of all unfertilized eggs obtained by hormone injection auto-activate. We expect these findings to aid in the conservation effort of Eleutherodactylus frogs, the largest vertebrate genus.

The Body Ear

From dusk until midnight, nearly every day of the year, a deafening din floods Puerto Rico's rain forests. Every few seconds, male Eleutherodactylus coqui frogs trumpet their co-qui mating call in competition with the blaring advertisements of seven other frog species and the dissonant chorus of rasping, chirping, buzzing insects. The animal orchestra creates such a loud cacophony that researchers working in the forest say they have a hard time hearing themselves think. Yet the male and female coqui frogs and their amphibian compatriots somehow sort through the pandemonium, separating the melodious acoustic wheat of their own species from the chaotic chaff of other creatures' chants. Exactly how the coqui and other frogs discriminate sounds in such noisy environments has long fascinated neuroethologist M. Narins at the University of California at Los Angeles (UCLA). He and others have found that amphibians employ a variety of communication strategies, including divvying up sound frequencies among different species, creating a louder fracas than their neighbors or producing periodic, easily recognizable calls. Most recently Narins and two associates have discovered that coqui frogs in particular may also be aided in pinpointing a sound's direction with an unusual sound pathway: through the lungs. They reported in the March PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES (Vol. 85, No.5) that when a sound wave hits a frog's side, it can travel through the airfilled lungs, up through the voice box, into the eustachian tubes and on to the eardrum. Peter and his colleagues have found what may be a totally unexpected medium for processing sound in these species of frogs, says Steven Greenberg, an auditory neurophysiologist at the University of Wisconsin in Madison. makes us rethink the ways in which sounds are localized in space, at least by frogs. This and findings in other animals are adding some interesting twists to the study of the evolution of hearing in vertebrates. Humans and most other mammals can tell a sound's direction by comparing the vibrations the sound waves induce in each eardrum. The waves entering the ear nearest the source are more intense and arrive sooner than do those entering the far ear. But to exploit this intensity and timing difference, the sound's wavelength must be much smaller than the distance between the ears. Since the upper audible limit of most mammals falls within 20,000 to 60,000 hertz, this condition is usually met in even the smallest mammals.