Leptodactylus fallax is one of the world's largest frogs, with adults reaching up to 210 mm SVL (Daltry and Gray 1999). Dorsal coloration is either uniform chestnut-brown or spotted and barred. Color becomes more orange-yellow laterally and reaches a pale yellow on the ventral side. Upper tibia may have broad banding. Males lack chest spines but have distal (metacarpal) cornified spurs on each hand (Kaiser 1994).
Leptodactylus fallax can be distinguished from other members of its genus by the following characteristics: dorsolateral folds running from eye to groin; lack of breast spines; lack of light striping on upper lip; elongated hind limbs; small dorsal and lateral tubercles; tympanic fold present but not prominent, curving sharply towards the angle of the jaw; pale ventrum; terrestrial foam nest created for egg deposition, in a burrow away from water; non-feeding larvae develop within the burrows (Kaiser 1994).
Lescure and Letellier (1983) determined that “tadpoles of L. fallax appear to be the longest of any species in the genus (110 mm at Gosner stage 42) with the tail amounting to 79-84% of their total length.”
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Dominica, Guadeloupe, Martinique, Montserrat, Saint Kitts and Nevis, Saint Lucia
Originally found on Dominica, Guadeloupe, Martinique, Montserrat, Saint Kitts and Nevis (Fa et al. 2004). Now confined to Dominica and Montserrat (Daltry and Gray 1999). On Dominica it occurs closer to sea level (but up to 400 m asl); on Montserrat it occurs primarily in the Centre Hills (northern Montserrat) from sea level to 430 m asl (Fa et al. 2004). Found in dense secondary vegetation, flooded forest, ravines, and on Dominica, in plantations (Fa et al. 2004).
Life History, Abundance, Activity, and Special Behaviors
This species is terrestrial and nocturnal, with terrestrial tadpoles, parental care, and obligatory oophagy by the larvae (Gibson and Buley 2004).
Males wrestle, with the dominant male making a "whooping" call and subsequently occupying the nesting burrow. The call then changes to a "trilling bark" (100-120 calls/min) to attract females to the burrow. Amplexing orientation varies initially, from head-to-head to head-to-vent, and stabilizes as head-to-head axillary amplexus. Nest production begins by the male stimulating the female’s cloaca by bringing both his hind feet in contact, to encourage fluid excretion. The male then engages in bouts of paddling with both hind legs, until the foam nest is complete (9-14 hours after the first attempt at amplexus). Both males and females call at periodic intervals while making the nest. Within 24 hours a “skin” has developed over the nest, sufficiently strong enough to support the female. The male leaves within a few minutes of the nest completion, while the female remains beside the nest, inside the burrow. Males remain outside the burrow, within a meter of the entrance, and defend the burrow if intruders approach. Females defend the nest if encroached upon.
Females rarely leave the nest, apparently doing so only to feed. Once larvae hatch, females begin provisioning the larvae with unfertilized eggs to feed on roughly once every three days (range 1-11 days). Tadpoles orient themselves around the mother's cloaca to feed on emerging trophic eggs. The female brushes her legs across the vent in alternating movements, sweeping the eggs throughout the nest, redistributing the nearby tadpoles, and renewing the foam. Larval tail movements may also help renew the foam during provisioning (foam is not produced when the mother is absent). Larval development is complete within 45 days, with 26-43 young froglets emerging from the burrow (Gibson and Buley 2004).
Although the nest itself contains only 26-43 tadpoles, it has been estimated that the mother will provision the developing tadpoles with a total of 10,000—25,000 unfertilized eggs to to feed on (assuming 10-13 provisioning events as the larvae develop; Gibson and Buley 2004).
Trends and Threats
Leptodactylus fallax has experienced a drastic decline in population--over 80% since 1995 (Gibson and Buley 2004). As of 1999, the species range had decreased to just 17 square kilometers on Montserrat (Daltry and Gray 1999). Volcanic eruptions began in July 1995 and have significantly impacted the habitat on Montserrat with lava flows, highly acid rain (pH as low as 2.0), toxic gases, and volcanic ashfall (Daltry and Gray 1999). L. fallax is a terrestrial breeder, with foam nests and eggs deposited in burrows, and volcanic ashfall was reported to have killed newly metamorphed froglets in 1995 (Daltry and Gray 1999). Since January 1998, monitoring has been conducted regularly by the Montserrat Forestry and Environment Division, in partnership with the organization Fauna and Flora International (Daltry and Gray 1999).
The final blow may be from chytridiomycosis, which broke out on Dominica in 2002 and spread throughout that island, eradicating nearly all Leptodactylus fallax within 15 months (Fa et al. 2004). Chytrid was recently introduced onto the island of Montserrat (thought to have been carried by a different frog species on bananas imported from Dominica), and has decimated all but two remaining populations on Montserrat (BBC news report 3/23/09). Captive populations of L. fallax exist at the Jersey Zoo (U.K.), where the Durrell Wildlife Conservation Trust has been breeding this species for some years, and the St. Louis Zoo (U.S.), among others (Fa et al. 2004).
Relation to Humans
This species was hunted for human consumption, giving rise to the common name "mountain chicken." The island of Dominica formerly had an estimated annual harvest of 8,000-36,000 animals (Fa et al. 2004).
Possible reasons for amphibian decline
General habitat alteration and loss
Intensified agriculture or grazing
Local pesticides, fertilizers, and pollutants
Intentional mortality (over-harvesting, pet trade or collecting)
Brooks, G.R. (1982). ''An analysis of prey consumed by the anuran, Leptodactylus fallax, from Dominica, West Indies.'' Biotropica, 14, 301-309.
Daltry, J. C., and Gerard, G. (1999). ''Effects of volcanic activity on the endangered Mountain Chicken Frog (Leptodactylus fallax).'' FROGLOG, 32.
Fa, J., Hedges, B., Ibéné, B., Breuil, M., Powell, R., and Magin, C. (2004). Leptodactylus fallax. In: IUCN 2008. 2008 IUCN Red List of Threatened Species. www.iucnredlist.org. Downloaded on 23 March 2009
Gibson, R.C., and Buley, K.R. (2004). ''Maternal care and obligatory oophagy in Leptodactylus fallax: A new reproductive mode in frogs.'' Copeia, 2004(1), 128-135.
Kaiser, H. (1994). '' Leptodactylus fallax.'' Catalogue of Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles, 583.1-583.3.
Lescure, J., and Letellier, F. (1983). ''Reproduction en captivité de Leptodactylus fallax Müller, 1926 (Amphibia, Leptodactylidae).'' Revue Française d'Aquariologie, Herpetologie, 10, 61-64.
Written by Zaina Khan and KU Herpetology Class (khanz AT berkeley.edu), UC Berkeley, U. of Kansas
First submitted 2004-12-14
Edited by Kellie Whittaker (2009-03-23)
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