Atelopus tricolor have a slim body and overall proportions. Male A. tricolor have a snout to vent length of 19.2 - 22.3 mm, whereas sampled A. tricolor females were slightly larger, being 29 - 36 mm respectively. The head is longer than it is broad and makes up one third of the snout to vent length. The snout is tapered and has a rounded tip. The upper jaw protrudes from the lower with a fleshy lip. The nostril is lateral, and the width of the eye is an equal distance as the distance between the nostril and the anterior edge of the eye. The pupil is horizontal. Atelopus tricolor has a postorbital crest that is not prominent. They have no tympanum. Overall, the body is slender. The tibia is about half the snout-vent length, and the foot is shorter than the tibia. The fingers are only basally webbed except for the short thumb, which about half the length of the hand and completely webbed excluding the tip. The tip of the thumb to the outer metatarsal tubercle is about half the width of the hand. The relative finger lengths are as follows: 1 < 2 < 4 < 3. Both palms and soles of the feet are relatively smooth with subarticular tubercles on the joints of some fingers and toes. They have long hindlimbs, with tibiotarsal articulation extending to at least the eye or beyond. The foot is shorter than the tibia. The feet have poorly developed metatarsal tubercles. The toes, except for toe tips, are completely webbed.The relative toe lengths are as follows: 1 < 2 < 3 < 5 < 4. Atelopus tricolor has small warts on its back, above the eye, on its sides and upper sides of the extremities. However, warts are absent from the tip of snout, ventral surfaces, and loreal region. The chest has wrinkled skin (Lotters and De la Riva 1998).
Atelopus tricolor adults can be distinguished from other similar Atelopus species by the present of warts on their skin and the stripes. Atelopus elegans and A. spumarius have smooth skin. Atelopus mindoensis has warts, but no stripes. Atelopus nicefori only has warts only on its flanks but not its back, and A. spumarius and A. amdinus are larger with shorter thumbs and only half-webbed toes (Lotters and De la Riva 1998).
In preservative, the frog is dark brown with two yellow dorsolateral stripes. These stripes are usually continuous but may be interrupted. Most specimens also have small spots on their bodies and limbs (Lotters and De la Riva 1998). Live specimens are greenish black with bright red-orange spotting; mustard-yellow bands (Reynalds and Foster 1992).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Bolivia, Peru
Atelopus tricolor is restricted to the Eastern Andes Mountains in Peru and nearby parts of Bolivia in humid montane forests at elevations of 600 – 2500 m above sea level close to short stream tracts with fast flow (Reynolds and Foster 1992, Lötters and De la Riva 1998, Stuart et al. 2008). A re-description of the species was made using specimens collected from the Cordillera Oriental area (Lotters and De la Riva 1998). The type specimen comes from the Mercapata Valley (Stuart et al. 2008), and the tadpoles that were collected and described were from Paucartambo, Departamento Cruzo, Peru and from the Noryungas Province, Departamento La Paz, Bolivia (Lavilla et al. 1997).
In humid montane forests, these frogs are abundant (Salas et al. 2004).
Life History, Abundance, Activity, and Special Behaviors
Adults are found both during the day and night around streams. They are commonly found 0.5 m above small fast-rushing streams, where breeding occurs (Reynolds and Foster 1992, Salas et al. 2004). The species has been observed in perches 0.3 – 1.2 m off the ground in disturbed primary forest and along secondary growth near roads. Males have been heard calling in groups of 4 – 10 individuals (Salas et al. 2004).
Several members of the genus Atelopus excrete the toxin, Atelopidotoxin. However, this toxin has not been studied in A. tricolor and it is currently unknown whether the species is toxic, but it is highly possible given that other members of this genus are known to have Atelopidotoxin (Fuhrman et. al. 1969).
Diagnostic features for A. tricolor tadpoles include a large, laterally expanded oral disc, one row of marginal papillae with a mental, but no rostral gap. They have a large abdominal sucker that is about as wide as the body, a low posteriorly displaced tail fin, and a medial vent. Perhaps one of the most unique features in this genus is the single submarginal papilla on either side of the oral disc. Although only 15% of the genus Atelopus tadpoles have been described, so far this feature seems to be unique to A. tricolor (Lavilla et al. 1997).
Tadpoles at Gosner’s stages 33 - 34 have a total length of 33.7 - 16.3 mm. Looking down at the dorsal surface of the tadpole, they appear to have an ovoid shape with two lateral constrictions: one after the eyes and another at the level of the spiracle. They have one spiracle on their left side that ends in a visible protruding tube on the last third of the body. Tadpoles of this species are wider than they are high. The height equals about 69% of maximum width, and the tail makes up about 56% the total length of the tadpole (Lavilla et al. 1997).
Tadpoles are dark brown with dark spots. Sides have non-pigmented areas. The venter is transparent with uniformly distributed dark spots. It has a non-pigmented stripe down the whole length. Transparent fins have scattered dark spots. They have a large abdominal sucker that is almost transparent with dark spots but no pigmented border. The tail is dark with unpigmented areas of variable sizes and shapes (Lavilla et al. 1997).
Tadpoles have been observed in the dry season. The sex ratio seems to favor many males to few females (Lötters and De la Riva 1998).
Trends and Threats
According to the IUCN Redlist, the primary reason for decline is habitat loss due to an increase in coffee, cocoa and chili pepper farming. However, A. tricolor can also be found in protected land (Salas et al. 2004, La Marca et al. 2005).
Atelopus has potential to be affected by diseases. This claim is justified due to the substantial declines in other species of Atelopus by the Chytrid fungus, Batrachochytrium dendrobatidis (Bd). Bd is believed to be able to spread to A. tricolor, however, out of 113 species, it is one of ten in the genus Atelopus that has not been affected by Bd (La Marca et al. 2005).
The species may also be threatened by introduced predatory trout (Salas et al. 2004).
Possible reasons for amphibian decline
General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Predators (natural or introduced)
Atelopus tricolor belongs to the family Bufonidae and was first described in 1902 by Boulenger. In a re-description of the species, Lötters and De La Riva (1998) concluded that both A. rugulosus and A. wilimanii are synonyms for A. tricolor.
Fuhrman, F. A., Fuhrman, G. J., and Mosher, H. S. (1969). ''Toxin from skin of frogs of the genus Atelopus: differentiation from dendrobatid toxins.'' Science, 165(3900), 1376-1377.
La Marca, E., Lötters, S., Puschendorf, R., Ibáñez, R., Rueda-Almonacid, J. V., Schulte, R., Marty, C., Castro, F., Manzanilla-Puppo, J., García-Pérez, J. E., Bolaños, F., Chaves, G., Pounds, J. A., Toral, E., and Young, B. E. (2005). ''Catastrophic population declines and extinctions in neotropical harlequin frogs (Bufonidae: Atelopus).'' Biotropica, 37(2), 190-201.
Lavilla, E. O., De Sa, R.O., De La Riva, I. (1997). ''Description of the tadpole of Atelopus tricolor.'' Journal of Herpetology, 31(1), 121-124.
Lötters, S., De La Riva, I. (1998). ''Redescription of Atelopus tricolor Boulenger from southeastern Peru and adjacent Bolivia, with comments on related forms.'' Journal of Herpetology, 32(4), 481-488.
Reynolds, R. P., Foster, M. S. (1992). ''Four new species of frogs and one new species of snake from the Chapare region of Bolivia, with notes on other species.'' Herpetological Monographs, 6, 83-104.
Salas, A., Ibáñez, R., Catenazzi, A., Chaparro-Auza, J.C., Angulo, A., Reichle, S., Köhler, J., De la Riva, I., Lötters, S., Cortez, C., Arizabal, W. (2004). Atelopus tricolor. The IUCN Red List of Threatened Species 2004: e.T54559A11167505. http://dx.doi.org/10.2305/IUCN.UK.2004.RLTS.T54559A11167505.en. Downloaded on 02 March 2016.
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.
Originally submitted by: Alaina Mikulcik, Elizabeth Malloy, Kristopher Spegal (first posted 2016-03-01)
Edited by: Ann T. Chang, Jarrett Johnson, Michelle S. Koo (2023-06-29)
Species Account Citation: AmphibiaWeb 2023 Atelopus tricolor: Tri-Colored Harlequin frog <https://amphibiaweb.org/species/87> University of California, Berkeley, CA, USA. Accessed Sep 24, 2023.
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Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 24 Sep 2023.
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