Wet Forest Toad, Dark Green Toad
© 2014 Eduardo Boza Oviedo (1 of 11)
Bufo melanochlorus is a relatively large toad with a snout-vent length of 73.6 mm for males and 106.7 mm for females. This species has a distinct sexual dimorphism. The females are larger than the males, but the males have longer heads. During the breeding season, males develop nuptial pads, consisting of dark, thickened patches on the dorsal surface of each thumb. Males also have more muscular forearms than the female. Females have more pairs of irregular black dorsal spots, a middorsal stripe, and a variable dorsal pattern (Guyer and Donnelly 2005; O'Neill and Mendelson 2004).
The dorsal skin is smooth, except for the scapular and iliac regions, which are unevenly covered with small, low, and rounded spiculae (O'Neill and Mendelson 2004; Cope 1877). The ventral skin is minutely roughened (Cope 1877). There is also a lateral row of tubercles consisting of a series of medium-sized, sharply pointed spicules (O'Neill and Mendelson 2004).
The head is greater in width than length, while its skin is co-ossified to the upper surface of the skull. It has well-developed cranial crests that are thin and high (O'Neill and Mendelson 2004). There are transverse folds between parietal, prolonged branch crests (O'Neill and Mendelson 2004; Cope 1877). The preorbital and pretympanic crests are absent in both sexes, but the canthal, supraorbital, and postpreorbital crests are well-developed. Bufo melanochlorus also has a small tympanum and elevated orbital borders (O'Neill and Mendelson 2004). The diameter of the distinctly round external tympanic disc is half that of the orbit (Savage 2002). The eyes are large and distinct, while the tongue is long and narrow (Savage 2002). The snout is rounded in profile, but has a dorsal outline that is sharply pointed in males and subelliptical in females (O'Neill and Mendelson 2004; Savage 2002). The vocal slits are small and bilateral with a large, unilobed, heavily pigmented, internal vocal sac (O'Neill and Mendelson 2004, Savage 2002). For males, this vocal sac becomes fully distended and round when calling. The parotoid glands are small (about 3/4 the size of the upper eyelid) and triangular with a row of low, rounded, lateral warts extending to the groin (O'Neill and Mendelson 2004; Savage 2002).
Finger I is longer than finger II and both have dark-brown nuptial pads on the upper surface in adult males. There are well-developed single subarticular and supernumerary tubercles under the fingers and the toes. Occasionally, the third finger has a subarticular tubercle as well (Savage 2002). Bufo melanochlorus has short hindlegs (Cope 1877). The upper surface of the hind limbs have many large pointed warts (Savage 2002). The tibia is short, only 45-50% of the SVL. The feet are relatively short as well (O'Neill and Mendelson 2004). The toes are long with some webbing (Cope 1877; Guyer and Donnelly 2005). The outer metatarsal tubercle is large and rounded, while the inner metatarsal tubercle is elevated and elongate (Savage 2002).
This species has a body color that is dominantly brown or gray with irregular dark gray or black blotches (Guyer and Donnelly 2004). It has a light, thick middorsal stripe, and paler gray dorsolateral stripes (O'Neill and Mendelson 2004). There is also a broad, dark lateral stripe that is bordered by light warts above. The venter is dark gray or brown with light flecks on the anterior side and light gray with mottled spots on the posterior side. The head is brown dorsally with distinct crests running from each nostril, behind the eye, to the back of the head. Each eye has a squarely-shaped, tan patch below it, extending to the upper lip, which separates a mottled dark brown region behind the eye to the ventral edge of the parotoid gland. This gives the frog an appearance of a black eye mask. The iris is coppery bronze with a black reticulum. The throat and chest are black, while the lower jaw has white spots along the ventral edge. The legs are mottled with light and dark brown colors (Guyer and Donnelly 2005). The tips of the digits are either the same color as the rest of the digits, or distinctly paler (O'Neill and Mendelson 2004). The juvenile is more brightly colored than the adult (Guyer and Donnelly 2005).
Bufo melanochlorus is similar to many other species, but can be distinguished by differences in morphology or color. The adult Bufo melanochlorus is similar to Bufo coniferus (Green Climbing Toad, also known as Ollotis conifera) in size, but has a first finger that is nearly as long as the third, longest finger, whereas the Green Climbing Toad has a shorter first finger. Bufo aucoinae is also similar, but male Bufo melanochlorus are larger, and all B. melanochlorus can be distinguished by having transverse folds between parietal crests, cranial crests that are elevated vertically, distinct pretympanic and preorbital crests, a black chest and throat, and mottling on the flanks (O'Neill and Mendelson 2004).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Costa Rica, Panama
This species occurs along the lowlands and premontane slopes of the Atlantic versant and lowland and premontane evergreen forests within the Pacific west of Costa Rica. Its range includes the Atlantic, montane slopes and Cordillera Central, and the extreme southern portion of the Pacific Northwest faunal areas of Costa Rica, as defined by Savage (2002). It is common at higher elevations within the wet forests, especially along the forest edge, and is found up to 1,080 meters above sea level. It is usually seen in association with large streams or occasionally found in forest litter (Guyer and Donnelly 2005; O'Neill and Mendelson 2004; McDiarmid and Savage 2005; Savage 2002).
Life History, Abundance, Activity, and Special Behaviors
Bufo melanochlorus is nocturnal and insectivorous (McDiarmid and Savage 2005).
The male calls during the dry season (January to February) from pools along rocky streams, within 0.5 meters of water (Savage 2002). Two males were also found calling from an open pond with several Bufo marinus in August (McDiarmid and Savage 2005). The call is similar to Bufo luetkenii and Bufo valliceps, consisting of a short trill lasting several seconds, repeated several times with intervals lasting a few seconds (Savage 2002). The male and female breed in fairly rocky-bottomed small streams at low water. Amplexus is axillary (Savage 2002).
Trends and Threats
The major threats to this species include alterations of its stream habitat due to pollution. The pathogen Batrachochytrium dendrobatidis has also been proposed as a potential future threat. This species occurs in Costa Rican National Parks and other protected areas, including La Selva and Monteverde, under population monitoring (IUCN 2006).
Possible reasons for amphibian decline
General habitat alteration and loss
A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).
Cope, E. D. (1877). ''Tenth contribution to the herpetology of tropical America.'' Proceedings of the American Philosophical Society, 17, 85.
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.
IUCN, Conservation International, and NatureServe. 2004. Global Amphibian Assessment. < www.globalamphibians.org >. Accessed on 28 November 2006.
McDiarmid, R.W., and Savage, J. M. (2005). ''The herpetofauna of the Rincon area, Peninsula de Osa, Costa Rica, a Central American lowland evergreen forest site.'' Ecology and evolution in the tropics: a herpetological perspective. A. G. Kluge, M. A. Donnelly, B. I. Crother, C. Guyer, and M. H. Wake, eds., University of Chicago Press, Chicago.
O'Neill, E. M. and Mendelson, J. R. (2004). ''Taxonomy of Costa Rican toads referred to Bufo melanochlorus Cope, with the description of a new species.'' Journal of Herpetology, 38(4), 487–494.
Savage, J. M. (2002). The Amphibians and Reptiles of Costa Rica. University of Chicago Press, Chicago and London.
Written by Stella Kim (stellaykim AT berkeley.edu), UC Berkeley
First submitted 2008-04-24
Edited by Kellie Whittaker (2009-11-02)
Species Account Citation: AmphibiaWeb 2009 Incilius melanochlorus: Wet Forest Toad <http://amphibiaweb.org/species/233> University of California, Berkeley, CA, USA. Accessed Mar 21, 2018.
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