Description
Phyllobates bicolor is a small frog, with males reaching an adult size of 32.1-39.5 mm and females reaching 35.7-42.7 mm (Myers et al. 1978). The skin is smooth (Silverstone 1976). Both premaxillary and maxillary teeth are present (Silverstone 1976). The first finger is longer than the second, and the digits have expanded discs (Silverstone 1976). Toes lack webbing (Silverstone 1976).

Phyllobates bicolor color patterning is very striking. The dorsum and sides are a uniform golden yellow or orange, as well as the dorsal surfaces of the upper arm and thigh (Myers et al. 1978). In contrast, the dorsal surfaces of the forearm and calf are black, and may or may not have dense yellow (or sometimes blue) spotting (Myers et al. 1978). The ventrum may be completely black, or washed with light orange, light gold, or bluish green (Myers et al. 1978). There is occasionally a black patch on the throat (Silverstone 1976). The tympanum is partly yellow-orange and partly black (Silverstone 1976). In some individuals, the tip of the snout is black (Silverstone 1976). Irises are black or reddish-brown (Silverstone 1976).

This species, like P. terribilis, exhibits an ontogenetic color change; juveniles are dark brown to black in color, with two yellowish dorsolateral bands. As the frogs reach maturity, the dorsolateral stripes disappear, and the frogs become more brightly colored. In contrast, the juvenile pattern of light stripes on a dark background is retained into adulthood in other members of the P. bicolor group, P. aurotaenia, P. lugubris and P. vittatus (Myers et al. 1978; Silverstone 1976).

Phyllobates bicolor closely resembles P. terribilis, but P. bicolor is smaller in size and has legs and venter of a different hue than the body color (Myers et al. 1978).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Colombia

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (2 records).

The Black Leg Poison Dart Frog lives in the tropical rain forests of Colombia, on the western side of the northern part of the Cordillera Occidental, between 25-1,525 m above sea level. It occurs in the upper Atrato and San Juan drainages, the Río Raposo, and headwaters of the Río Sipí, in the Cordillera Occidental. This species inhabits the forest floor (Silverstone 1976; Myers et al. 1978). It is reported to survive in logged forest but not open habitat (IUCN 2006).

Life History, Abundance, Activity, and Special Behaviors

Like other dendrobatids, Phyllobates bicolor are diurnal and are very active. Little has been published on the reproductive behavior of this species in the wild. Zimmermann (1989) has published sonograms of P. bicolor calls, and reports that in captivity, P. bicolor, males initiate courtship by giving a "long-range" courtship call. The female then follows the male to a covered egg deposition site. Once the female approaches within 8 cm, the male emits a "short-range" courtship croak call, ceasing before the female oviposits. Circling and body-anal touching was observed but not amplexus. In captivity, a single female may lay up to three clutches of 12-20 eggs per month. The male moistens the clutch at irregular intervals (hydric brooding). Tadpoles hatch in about 14 days, after which the male transports them to a water-filled brooding site (Zimmermann 1989).

Trends and Threats
It occurs in one protected area, the Parque Nacional Natural Farallones de Cali. Major threats include habitat alteration due to deforestation for agriculture and logging, and human settlement; pollution from spraying illegal crops; and introduction of non-native predatory fish. Collection for the international pet trade occurs but it is difficult to assess the extent of this threat. Chytridiomycosis may be a potential future threat (IUCN 2006).

Relation to Humans
Phyllobates bicolor is one of only three species of frog (P. terribilis, P. aurotaenia, and P. bicolor) that have been documented as used by humans to poison darts. All are from the Pacific versant of Colombia, and used by various tribes of the Chocó Indians in western Colombia. All three species have high levels of batrachotoxins, with P. terribilis by far the most toxic and the other two species approximately equal in toxicity to each other. Phyllobates terribilis contains 700-1900 micrograms of batrachotoxin-homobatrachotoxin per frog, whereas P. bicolor contains 17-56 micrograms of combined toxins per frog. Batrachotoxin-containing skin secretions for poisoning dart tips are obtained either by simply rubbing the tip on the live frog's back (P. terribilis), or impaling the frog and also sometimes heating it (P. bicolor and P. aurotaenia) (Myers et al. 1978).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Habitat fragmentation
Local pesticides, fertilizers, and pollutants
Predators (natural or introduced)
Intentional mortality (over-harvesting, pet trade or collecting)

Comments

As is true of other species in the genus Phyllobates, this species produces batrachotoxins. However, captive-born and bred dendrobatid frogs lack toxicity, since the toxins are acquired at least in part from dietary sources such as ants, mites or beetles (Daly et al. 1980; Daly et al. 1992; Dumbacher et al. 2004). In contrast, the toxins persist in wild-caught animals even when they are maintained in captivity (Daly et al. 1978).

Myers et al. (1978) have speculated that there might be either hybridization or a cline between P. bicolor and P. aurotaenia in the upper San Juan drainage, due to the intermediate size and coloration of the Phyllobates found there.

References

Daly, J. W., Myers, C. W., Warnick, J. E., and Albuquerque, E. X. (1980). ''Levels of batrachotoxin and lack of sensitivity to its action in poison-dart frogs (Phyllobates).'' Science, 208, 1383-1385.

Daly, J.W., Secunda, S.I., Garraffo, H.M., Spande, T.F., Wisnieski, A., Nishihara, C., and Cover, J.F. (1992). ''Variability in alkaloid profiles in neotropical poison dart frogs (Dendrobatidae): genetic versus environmental determinants.'' Toxicon, 30, 887-898.

Dumbacher, J.P., Wako, A., Derrickson, S.R., Samuelson, A., Spande, T.F., and Daly, J.W (2004). ''Melyrid beetles (Choresine): a putative source for the batrachotoxin alkaloids found in poison-dart frogs and toxic passerine birds.'' Proceedings of the National Academy of Sciences of the United States of America, 101, 15857–15860.

IUCN, Conservation International, and NatureServe. (2006). Global Amphibian Assessment: Phyllobates bicolor. www.globalamphibians.org. Accessed on 7 May 2008.

Myers, C. W., Daly, J. W., and Malkin, B. (1978). ''A dangerously toxic new frog (Phyllobates) used by Emberá Indians of Western Colombia, with discussion of blowgun fabrication and dart poisoning.'' Bulletin of the American Museum of Natural History, 161, 307-366.

Silverstone, P.A. (1976). ''A revision of the poison arrow frogs of the genus Phyllobates Bibron in Sagra (Family Dendrobatidae).'' Natural History Museum of Los Angeles County Science Bulletin, 27, 1-53.

Zimmermann, H. (1989). ''Conservation studies on the 'dart-poison' frogs Dendrobatidae in the field and in captivity.'' International Zoo Yearbook, 28, 31-44.

Species Account Citation: AmphibiaWeb 2009 Phyllobates bicolor: Black Leg Poison Dart Frog <https://amphibiaweb.org/species/1705> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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