Craugastor ranoides (Cope, 1886)
© 2005 Robert Puschendorf (1 of 11)
Diagnosis: Adult males are small to moderate-sized (26-45 mm SVL), while adult females are large (40-74 mm) frogs; this species can be distinguished from other members of the rugulosus group by having a dark posterior thigh surface with small, discrete, light spots, and adult males lacking vocal sacs, vocal slits, and nuptial pads (Savage 2002).
Description: Males 26-45 mm SVL, females 40-74 mm SVL as adults. Head is roughly equivalent in length and width. Snout subovoid to rounded in dorsal view. Eyes are large. Upper eyelid is granulate to tuberculate. Tympanum is round in males, oval in females. Finger I is longer than finger II. Fingers have rounded, defined disc covers that are 1.5x digit width for fingers III and IV. Subarticular tubercles are rounded and do not project. Supernumerary tubercles are absent on the hands. Palmar and thenar tubercles are elongated. Modal webbing formula: I 2-2 1/2 II 2--3+ III 3-4 IV 4-2 1/2 V. Toes have rounded, defined disc covers that are 1.5x digit width for toes III, IV, and V. Subarticular tubercles on feet are rounded and do not project. Supernumerary tubercles are absent on the feet. Inner metatarsal tubercle is large, while the outer metatarsal tubercle is very small. Inner tarsal fold is strong. Dorsum is smooth to granulate and the venter is smooth. Nuptial pads, vocal sacs, and vocal slits are lacking in adult males.
Coloration is dark olive green or olive brown on the dorsum. The dorsum may be uniform or may be spotted or blotched with darker pigment. Limbs have dark transverse bars on the upper surfaces. Posterior thigh surfaces are dark brown with highly contrasting small light spots. The venter is pale yellow or bright yellow-gold. The iris is gold above and dark brown below. There is some variation in ventral coloration within Costa Rican populations; those that are from farther south in Costa Rica and into Panama have the bright yellow-gold venters (Savage 2002).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Costa Rica, Nicaragua, Panama
The species is associated with small streams mostly in lowland and premontane wet forests. However, it can also be found in dry forest with perennial streams. It is often found on rocks and under boulders in the stream. The only known remaining site in Costa Rica is dry forest that has a constant flowing stream and a water temperature that is higher than other sites in Costa Rica from which the species has disappeared (Stuart et al. 2008).
Life History, Abundance, Activity, and Special Behaviors
Craugastor ranoides is active at night, foraging along streams. When disturbed, it jumps into the water (Savage 2002). It is presumed to breed by direct development, like other species in its genus (Stuart et al. 2008). Because adult males lack vocal slits and vocal sacs, this species is thought to be mute (Savage 2002).
The species was formerly widespread in Costa Rica but has not been seen in much of its range since 1986. Sites where it was formerly present have been searched repeatedly in the last decade with no success (Stuart et al. 2008).
Trends and Threats
Although destruction of natural forests for agriculture and timber has contributed to the decline of this species, it has also disappeared rapidly from pristine habitats (Stuart et al. 2008). Other species of Craugastor have also undergone dramatic declines and disappearances, especially those associated with streams; these declines are thought to be due to chytridiomycosis (Stuart et al. 2008). A small population appears to be persisting in several streams in the Guanacaste area, at Río Murciélago on the seasonally hot and dry Santa Elena Peninsula (Puschendorf et al. 2005; Zumbato-Ulate et al. 2007), a region predicted by climatic modeling to be inhospitable to the chytrid fungus (Puschendorf et al. 2009). Individuals were recorded at Río Murciélago in 1994, 1995, and 2003 (Sasa and Solórzano 1995; Puschendorf et al. 2005; Zumbado-Ulate et al. 2007) and this population should be monitored (Stuart et al. 2008). In contrast, populations in the nearby Guanacaste Volcanic Chain (a colder and more humid environment) have disappeared (Puschendorf et al. 2009). The statuses of populations in Nicaragua and Panama are unknown (Stuart et al. 2008).
Possible reasons for amphibian decline
General habitat alteration and loss
The karyotype of Costa Rican populations is 2N=20, with six pairs of metacentric chromosomes, one pair of submetacentrics, one pair of subtelocentrics, and two pairs of telocentrics, while NF = 36 (DeWeese 1976).
A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).
Campbell, J. A. and Savage, J. M. (2000). ''Taxonomic reconsideration of the Middle American frogs of the Eleutherodactulus rugulosus (Anura: Leptodactylidae): A reconnaissance of subtle nuances among frogs.'' Herpetologocal Monographs, 14, 186-292.
Cope, E. D. (1886). ''Thirteenth contribution to the herpetology of tropical America.'' Proceedings of the American Philosophical Society, 23, 271-287.
DeWeese, J. E. (1976). The Karyotypes of Middle American Frogs of the Genus Eleutherodactylus (Anura: Leptodactylidae): A Case Study of the Significance of the Karyological Method. Ph. D. dissertation, University of Southern California.
Puschendorf, R., Carnaval, A. C., VanDerWal, J., Zumbado-Ulate, H., Chaves, G., Bolaños, F., and Alford, R. A. (2009). ''Distribution models for the amphibian chytrid Batrachochytrium dendrobatidis in Costa Rica: proposing climatic refuges as a conservation tool.'' Diversity and Distributions, 15, 401-408.
Puschendorf, R., Chaves, G., Crawford, A .J. and Brooks, D. R. (2005). ''Eleutherodactylus ranoides (NCN). Dry forest population, refuge from decline?'' Herpetological Review, 36, 53.
Sasa, M. and Solorzano, A. (1995). ''The reptiles and amphibians of Santa Rosa National Park, Costa Rica, with comments about the herpetofauna of xerophytic areas.'' Herpetological Natural History, 3, 113-126.
Savage, J. M. (2002). The Amphibians and Reptiles of Costa Rica:a herpetofauna between two continents, between two seas. University of Chicago Press, Chicago, Illinois, USA and London.
Stuart, S., Hoffmann, M., Chanson, J., Cox, N., Berridge, R., Ramani, P., Young, B. (eds) (2008). Threatened Amphibians of the World. Lynx Edicions, IUCN, and Conservation International, Barcelona, Spain; Gland, Switzerland; and Arlington, Virginia, USA.
Zumbado-Ulate, H., Puschendorf, R. and Chavarría, M. M. (2007). ''Eleutherodactylus ranoides (NCN) distribution.'' Herpetological Review, 38, 184-185.
Originally submitted by: Aisha Butt and Kellie Whittaker (first posted 2009-11-02)
Edited by: Kellie Whittaker (2011-09-12)
Species Account Citation: AmphibiaWeb 2011 Craugastor ranoides <https://amphibiaweb.org/species/6154> University of California, Berkeley, CA, USA. Accessed Dec 3, 2023.
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Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 3 Dec 2023.
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