Rana vaillanti is a large frog with males reaching 67-94 mm and females 76-125 mm in snout-vent length (Savage 2002). The head is longer than wide, with a pointed snout. The tympanum is large, and exceeds or is equal to the eye diameter. Fingers are unwebbed but have a lateral ridge, and also have slightly swollen tips. Finger I is longer than finger II. Subarticular tubercles are present under fingers but no supernumerary, plantar, or accessory palmar tubercles are present. The thenar tubercle is elongated and the palmar tubercle is cordate to bifid. On the hindlimb, a weak tarsal ridge is present. Toes have expanded tips and are fully webbed, with oblong subarticular tubercles. The inner metatarsal tubercle is present and elongate, but the outer metatarsal tubercle is lacking. Dorsal surfaces on this frog are covered with white-tipped denticles, particularly between the two prominent dorsolateral folds. The shank bears longitudinal rows of white-tipped denticles on the dorsal surface. Ventrally most surfaces are smooth, but the underside of the tarsus is denticulate. Males have paired rounded vocal slits and paired internal subgular vocal sacs, as well as yellowish nuptial excrescences on the dorsolateral surface of the thumb and forearm (Savage 2002).
This frog has a tannish brown dorsum with an anterior greenish cast, often containing small, black punctations that border the outside of the paired dorsolateral ridges (Savage 2002). Sexual dichromatism is present; males have a brighter green dorsum while females have a gray-brown dorsal coloration with green only along the edges (Ramirez et al. 1998). Scattered brown markings may be present posteriorly (Savage 2002). The top of the head and the sides of the face are green (Guyer and Donnelly 2005). The upper lip is a uniform grayish green color while the lower lip is either white or gray, extending as a strip to the anterior portion of the upper arm (Guyer and Donnelly 2005). The dorsal quarter of the iris is yellow, which stands out against the green color of the face (Guyer and Donnelly 2005). The venter may be a lighter yellow or even white, with much of the ventral side mottled with light and dark gray (Guyer and Donnelly 2005). Legs have transverse dark bars (Savage 2002), and the posterior thighs are dark gray with yellow reticula (Guyer and Donnelly 2005).
Sexual dimorphism is present as well; the female is larger than the male, and males have larger tympana, while females have tympanic diameters that are equal to or smaller than the orbit diameter (Ramirez et al. 1998). Breeding males also have a thickened, darker nuptial pad along the inside of each thumb and thicker forearms than the female (Guyer and Donnelly 2005).
Juvenile coloration tends to be of a brighter shade of green than the adult, so that the body is dark green with a wide, tan strip between the dorsolateral ridges, which contain small, black punctations. The sides of the juvenile body are brownish gray with yellow lips. The side of the face is green, bordered dorsally by a distinct black line that runs from the naris to the eye (Guyer and Donnelly 2005).
This species has very large larvae, reaching 80 mm in total length. The larval body is ovoid. The eyes and nostrils are dorsal. The mouth is ventral, with a moderate, emarginate oral disc having finely serrated beaks and 4/4 rows of denticles. Denticle rows A2-A4 are interrupted, either medially above the mouth or by the mouth, while row P1 is interrupted medially below the mouth. Papillae are present in three lateral rows on each side. The spiracle is sinistral and low, located near the level of the eye, and the vent is dextral. The tail is of moderate length with deep tail fins and a rounded tail tip. Dorsally and laterally, the body is dark, with irregular dark blotches; the tail musculature and fins also have large dark blotches (Savage 2002).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Belize, Colombia, Costa Rica, Ecuador, Guatemala, Honduras, Mexico, Nicaragua, Panama
This species resides on the Caribbean slopes from Veracruz, Mexico to northern Colombia and on the Pacific slopes from Oaxaca, Mexico to Ecuador (Goldberg 2002), at elevations up to 700 m (Savage 2002). It is found associated with deeper pools of stagnant or slow-moving water (Guyer and Donnelly 2005), as well as slow-moving streams and rivers (Leenders 2001) in lowland forests and marginally in premontane rainforest (Savage 2002).
Life History, Abundance, Activity, and Special Behaviors
Rana vaillanti is semiaquatic, found either at the water's edge on land, resting in shallows, or floating among vegetation with only its green head emerging (Savage 2002). It is active throughout the year both during day and night (Ramirez et al. 1998). When startled, if it is on land, it will escape into the water to swim a short distance to a hiding spot on the bottom of the lake (Leenders 2001) or under floating vegetation (Savage 2002). This frog is a sit-and-wait predator with a diverse diet of mainly sedentary prey, including a high proportion of invertebrates such as insects (coleopterans, odontates and areneids) and spiders, but also including birds, fish, and conspecifics (Ramirez et al. 1998). It forages on the shoreline of the lake, leaping with hind legs completely extended (Guyer and Donnelly 2005).
Males call from floating vegetation, or the shore, both day and night but more frequently at night during the breeding season (Savage 2002). The advertisement and territorial call consists of a complex series of squalls and chortles, with the variability of noises giving the impression that several species are present at the same time (Guyer and Donnelly 2005). The call may even be reminiscent of sounds produced by rubbing a hand across an inflated balloon (Guyer and Donnelly 2005). This frog also gives a high-pitched, single-note alarm call sounding like a 'yip' while leaping toward safety, and a captured individual may give prolonged, high-pitched calls while being handled by its captors (Guyer and Donnelly 2005). The call given by this frog at La Selva, Costa Rica is similar to that of Taylor's Leopard Frog (Rana taylori, formerly Rana pipiens) and its relatives (Guyer and Donnelly 2005).
Breeding season lasts from June to August at least (the wet season) and may extend throughout the year (Savage 2002; Ramirez et al. 1998). The female deposits the clutch of about 1000 eggs in the water as a large clump (Guyer and Donnelly 2005; Leenders 2001).
In a study examining the population biology of Rana vaillanti in a permanent lake in southern Veracruz, Mexico, a low recruitment rate of only 28 individuals per year was found, indicating a stable population with little emigration. There is relatively low adult mortality and the population remains stable during the adult phase of the life cycle. Predation is the major cause of mortality, particularly by the following snake species: Clelia scytalina, Drymarcon corais melanurus, Drymobius margaritiferus, Leptodeira annulata, Leptophis mexicanus, Leptophis ahaetulla, and Dryadophis melanolomus.
In contrast, parasites are not a major cause of mortality. This frog has relatively few parasites in comparison to other species of frogs, despite its aquatic lifestyle which favors the life cycle of Gorgoderina and many other digeneans. Studies have reported only 25 helminth species parasitizing Rana vaillanti including several species of Gorgoderina: G. attenuata, G. diaster, G. parvicava, and G. megacetabularis. The site of infection is the urinary bladder (Ramirez et al. 1998; Mata-LÃ³pez et al. 2005).
In Costa Rica, Rana vaillanti is one of the most common ranids at La Selva in the Cantarana and Research swamps and may be encountered by day or night on the boardwalk, on logs or floating vegetation, or at the water's surface (Guyer and Donnelly 2005).
Trends and Threats
This species is very adaptable with minimal threats except for pollution and invasive species such as Rana catesbeiana (IUCN 2006).
Possible reasons for amphibian decline
General habitat alteration and loss
Predators (natural or introduced)
Previous species lists may refer to this frog as Rana palmipes (Guyer and Donnelly 2005). Savage (2002) and Guyer and Donnelly (2005) follow the systematic treatment of Hillis and de SÃ¡ (1988), in separating the two species based on morphology.
A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).
Goldberg, S. R., Bursey, C. R., Salgado-Maldonado, G. , Baez, R., and Caneda, C. (2002). ''Helminth parasites of six species of anurans from Los Tuxtlas and Catemaco Lake, Veracruz, Mexico.'' The Southwestern Naturalist, 47, 293-299.
Guyer, C., and Donnelly, M. A. (2005). Amphibians and Reptiles of La Selva, Costa Rica and the Caribbean Slope: A Comprehensive Guide. University of California Press, Berkeley.
Hillis, D. M. and De Sa, R. (1988). ''Phylogeny and taxonomy of the Rana palmipes Group (Salientia: Ranidae).'' Herpetological Monographs, (2), 1-26.
IUCN, Conservation International, and NatureServe. (2006). Global Amphibian Assessment: Rana vaillanti. www.globalamphibians.org. Accessed on 2 March 2008.
Leenders, T. (2001). A Guide to Amphibians And Reptiles of Costa Rica. Zona Tropical, Miami.
Mata-López, R., León-Règagnon, V., and Brooks, D. R. (2005). ''Species of Gorgoderina (Digenea: Gorgoridae) in Rana vaillanti and Rana cf. forreri (Anura: Ranidae) from Guanacaste, Costa Rica, including a description of a new species.'' The Journal of Parasitology, 91, 403.
Ramirez, J., Vogt, R. C. and Villarreal-Benitez, J. (1998). ''Population biology of a neotropical frog (Rana vaillanti).'' Journal of Herpetology, 32, 338-344.
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.
Originally submitted by: Stella Kim (first posted 2008-04-24)
Edited by: Kellie Whittaker (2009-11-02)
Species Account Citation: AmphibiaWeb 2009 Rana vaillanti: Vaillant's frog <https://amphibiaweb.org/species/5176> University of California, Berkeley, CA, USA. Accessed Jul 29, 2021.
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Citation: AmphibiaWeb. 2021. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 29 Jul 2021.
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