Melodious Coqui, Wrinkled Coqui, Wightman’s Robber Frog, Coqui Melodioso
© 2004 Luis J. Villanueva-Rivera (1 of 1)
Adult Morphology: On average, E. wightmanae measures 19 mm (3/4 inch) in total body length (Rivero 1998), with females measuring a maximum of 22.5 mm SVL (Joglar et al. 2005). The head is slightly smaller than the body, and the eyes protrude from the head (Joglar 1983). Pupils are oval-shaped and horizontal. The tympanum is not distinct. The forelimbs are very slender but the hind limbs are more robust. Digits are long and slender and bear circummarginal discs, with Toe III being the longest on the hind limbs (Joglar 1983). Digital pads are slightly enlarged on the fingers but are much smaller than similar species (E. coqui and E. cooki), which reflects its life on the ground or in small bushes (Miranda-Castro et al. 2000). The texture of the skin on the dorsal surface is fairly warty while the ventral surface is granular (Joglar 1983). Males have a single external vocal sac for calling (Joglar 1983).
Adult Coloration: The dorsal surface is brown or gray in background color, with small dark spots on the back and flanks, and often a tinge of salmon or rosy yellow (Schmidt 1920; Rivero 1998). Limbs are barred on the thighs and tibia (Rivero 1998). The ventral surface is white to a greenish-yellow color (Rivero 1998). The upper eye is golden or golden-gray in color (Rivero 1998). Behind the tympanum is a dark line and on the dorsal surface of the hind limbs are dark bands (Schmidt 1920; Rivero 1998). Males have a gray throat with green flecks, yellow-green abdomen and yellow-green (or yellow with a touch of rosiness or salmon) ventral surfaces on the extremities (Rivero 1998).
Larval Morphology/Coloration: no larval stage; direct development (Joglar et al. 2005).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Puerto Rico
Eleutherodactylus wightmanae is found in Puerto Rico, in the interior, forested highlands of the island. Unfortunately, only 1% of the original forest remains on the island, but protected areas such as the Caribbean National Forest and the Guanica State Forest provide shelter for the remaining flora and fauna, including this small frog (Miranda-Castro et al. 2000). The melodious coqui is also very prevalent in the El Yunque National Forest (Burrowes et al. 2004). Recently, Los Tres Picachos Forest was added as a protected site and here E. wightmanae is found in abundance (although in other localities in Puerto Rico its numbers are declining). Los Tres Picachos Forest is situated between the cities of Ciales and Jayuya in the Cordillera Central of Puerto Rico, at elevations ranging from approximately 1250 to 3900 feet (380 to 1205 m) above sea level. The forest is classified as a subtropical wet forest and receives an average of 78 to 157 inches (2000-4000 mm) of rainfall annually. In addition, the average temperature is 64* to 75*F (18-24*C) (Miranda-Castro et al. 2000).
The land surrounding the reserve is primarily agricultural, mainly shaded coffee, citrus, plantain, and banana plantations. The forest within the reserve has three predominant vegetation types, depending on elevation: above 3300 feet (1000 m) asl, elfin woodland or dwarf forest predominates; from 2800 to 3300 feet (850 to 1000 m) asl, Sierra palm (Prestoea montana) forest is the primary vegetation; and from 2300 to 2800 feet (700-850 m) asl, the tabonuco tree (Dacryodes excels) is predominant (Miranda-Castro et al. 2000). Anything below this elevation has been converted to agricultural land. E. wightmanaegenerally occurs between 1000 feet (305 m) and 3900 feet (1189 m) asl (Schwartz and Henderson 1991).
Life History, Abundance, Activity, and Special Behaviors
Reproduction: Females will deposit eggs on the inside of folded Cecropia leaves that are strewn about the forest floor, usually 4-5 eggs per leaf (Joglar et al. 2005). Females deposit up to 30 fertilized eggs in all (Rivero 1998). The size of the individual eggs range from 4.31 to 3.52 mm in diameter, with a mean diameter of 4.39 mm (Joglar et al. 2005). Embryos undergo direct development, bypassing the tadpole stage (Joglar et al. 2005).
Diet: E. wightmanae feeds upon insects it finds in the soil and leaf litter, mainly on those found in the following taxa: Orthoptera, Psocoptera, Coleoptera, Homoptera, Diptera, Hymenoptera, Lepidoptera, and Isoptera. Adults also feed on small spiders, mites, and other invertebrates (Lavigne and Drewry 1970). A more recent study by Stewart and Woolbright (1996) confirmed these food sources, and added that the classes Chilopoda and Diplopoda (centipedes and millipedes, respectively) make up 30.7% of the diet.
Calls: Males of this species have a beautiful, clear advertisement call which they emit from a perch, usually a bush or log, not more than 0.6 m from the ground (Joglar et al. 2005). The coquis of Puerto Rico get their name from the “ko-kee” sound of their call, but in reality only 2 of the 16 species (Joglar 1983, see Fig. 1) of Puerto Rican Eleutherodactylus actually have this sound to their calls (Rivero 1998). The call consists of 3-10 high-pitched whistling notes, with the first two at a lower pitch and nearly inaudible, then with notes gradually increasing in pitch (Rivero 1998). At the end of the call, the last notes may decrease in tone, which is reminiscent of a ventriloquist's voice and makes it difficult to find this frog calling in the woods (Rivero 1998). Males will join together in a chorus so that the forest seems to be filled with the tinkling of bells (Schwartz and Henderson 1991). The sound of a passing car can also stimulate calling (Rivero 1998).
Trends and Threats
The major threat to E. wightmanae is habitat loss due to the increasing human population on the rather small island of Puerto Rico. It does occur within several protected areas: Maricao Forest and Guilarte Forest (Vilella and Fogarty 2005), Guanica State Forest (Miranda-Castro et al. 2000), Carite Forest Reserve (Joglar et al. 2005), Caribbean National Forest (Miranda-Castro et al. 2000), El Yunque National Forest (Burrowes et al. 2004), and Los Tres Picachos Forest (Miranda-Castro et al. 2000).
It has been proposed that hurricanes, common for islands in the middle of the Caribbean, may pose a threat to this species. Rivero (1998) thought that Hurricane Hugo (1989) had not affected this species, perhaps because branches and litter deposited on the ground afforded protection. Other workers found small decreases after Hurricane Hugo and Hurricane Georges (1998) but concluded that this species was still present at roughly the same abundance (Woolbright 1991; Vilella and Fogarty 2005).
Climate change may affect this species via causing drought. Although frogs can be adapted to live on land without being near a major water source, their skin still must be sufficiently moist to prevent desiccation of their bodies and their eggs. The frogs of Puerto Rico are adapted to a mesic lifestyle and rely on condensation of vegetation to stay moist (Burrowes et al. 2004). However, the lack of appropriate rainfall and humidity associated with droughts cause problems for the frog species of the island. Droughts cause members of a species to cluster in a small, humid area instead of dispersing over a larger area. The damp and close proximity can facilitate disease, which quickly gets spread to others (Burrowes et al. 2004). One very lethal disease that is spreading rapidly around Puerto Rico and other parts of the world is chytridiomycosis, caused by the pathogenic chytrid fungus Batrachochytrium dendrobatidis, which grows on frog skin and efficiently prevents rehydration (as well as respiration) (Voyles et al. 2009). The frog dies but the fungus remains to be passed on to its neighbors. Unfortunately, global climate change is causing more prolonged droughts in moist, tropical areas such as Puerto Rico, which may in turn increase the occurrence of chytridiomycosis, further endangering these endemic amphibians (Burrowes et. al. 2004).
Possible reasons for amphibian decline
General habitat alteration and loss
Phylogenetic Relationships: Joglar (1983) examined the phylogenetic relationships within the Eleutherodactylus genus of Puerto Rico. In this paper, E. wightmanae was classified into the auriculatus group, along with ten other species. Morphological characters defining this group included a granular abdomen, patches of vomerine odontoids , well-developed toe pads, and vocal sacs in males. Ecological characteristics of this group included having a male advertisement call, and calling from above the ground. E. wightmanae was found to be most closely related to E. eneidae, E. portoricensis, and E. coqui.
Etymology: Eleutherodactylus is derived from a Greek word meaning “free-toed,” while wightmanae honors Margaret Wightman Schmidt, the wife of the scientist who discovered this frog in 1919 (Schmidt 1920).
Burrowes, P. A., Joglar, R. L., and Green, D. E. (2004). ''Potential causes for amphibian declines in Puerto Rico.'' Herpetologica, 60, 141-154.
Joglar, R. (1983). ''Phenetic study of the genus Eleutherodactylus in Puerto Rico.'' Caribbean Journal of Science , 19, 33-40.
Joglar, R., Burrowes, P., Davila, D., Rodriguez, A., Lopez, A., Longo, A., and Medina, P. (2005). ''Eleutherodactylus wightmanae (Coqui Melodioso) reproduction.'' Herpetological Review, 36, 433-434.
Lavigne, R., and Drewry, G. (1970). ''Feeding behavior of the frogs and lizards in the tropical wet forest-preliminary report .'' The Rain Forest Project Annual Report. Puerto Rico Nuclear Center, San Juan, 64-73.
Miranda-Castro, L., Puente-Rolon, A.R., and Vega-Castillo, S. (2000). ''First list of the vertebrates of Los Tres Picachos State Forest, Puerto Rico, with data on relative abundance and altitudinal distribution .'' Caribbean Journal of Science , 36, 117-126.
Rivero, J., Oliver, L., and de los Angeles Irizarry, M. (1987). ''Toe pads of 3 species of Eleutherodactylus (Anura Leptodactylidae) from Puerto Rico with notes on adhesion mechanisms in frogs.'' Caribbean Journal of Science, 23, 226-237.
Rivero, J.A. (1998). Los Anfibios y Reptiles de Puerto Rico. University of Puerto Rico Press
Schmidt, K. (1920). ''Contributions to the herpetology of Porto Rico.'' Annals of the New York Academy of Sciences, 28, 167-200.
Schwartz, A., and Henderson, R. W. (1991). Amphibians and Reptiles of the West Indies. Descriptions, Distributions, and Natural History. University of Florida Press, Gainesville, Florida, USA.
Stewart, M. and Woolbright, L. (1996). ''Amphibians.'' The Food Web of a Tropical Rain Forest. D.P. Reagan and R.B. Waide , eds., University of Chicago Press, Chicago, 273-320.
Stuart, S., Hoffmann, M., Chanson, J., Cox, N., Berridge, R., Ramani, P., and Young, B. (eds) (2008). Threatened Amphibians of the World. Lynx Edicions, IUCN, and Conservation International, Barcelona, Spain; Gland, Switzerland; and Arlington, Virginia, USA.
Vilella, F. and Fogarty, J. (2005). ''Diversity and abundance of forest frogs (Anura: Leptodactyli- dae) before and after Hurricane Georges in the Cordillera Central of Puerto Rico .'' Caribbean Journal of Science , 41, 157-162.
Voyles, J., Young, S., Berger, L., Campbell, C., Voyles, W. F., Dinudom, A., Cook, D., Webb, R., Alford, R. A., Skerratt, L. F., and Speare, R. (2009). ''Pathogenesis of chytridiomycosis, a cause of catastrophic amphibian declines.'' Science, 326, 582-585.
Woolbright, L. L. (1991). "The impact of Hurricane Hugo on forest frogs in Puerto Rico." Biotropica, 23, 462-467.
Written by Madeline C. Bantly (mbantly AT csustan.edu), California State University Stanislaus
First submitted 2011-06-23
Edited by Kellie Whittaker (2012-01-26)
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