Leptodactylus fallax 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Amphibia Anura Leptodactylidae

Scientific Name: Leptodactylus fallax Müller, 1926
Common Name(s):
English Mountain Chicken, Giant Ditch Frog
Taxonomic Source(s): Frost, D.R. 2014. Amphibian Species of the World: an Online Reference. Version 6 (27 January 2014). New York, USA. Available at: (Accessed: 27 January 2014).

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2ace; C2a(i) ver 3.1
Year Published: 2017
Date Assessed: 2017-08-15
Assessor(s): IUCN SSC Amphibian Specialist Group
Reviewer(s): Luedtke, J.
Contributor(s): Ibene, B., Hedges, B., Magin, C., Dawson, J.S., Fa, J., Breuil, M., Hudson, M. & Powell, R.
Facilitator/Compiler(s): Hobin, L.
This is a large, visible species that has been well-surveyed in recent years with monthly monitoring on Dominica since 2014. Therefore the current population estimate of 132 individuals is accurate a figure as can be obtained for this species. The population crash on Dominica between 2002-2004 resulted in near-extinction (decline of at least 80%) with population levels being extremely low such that the species was not detected during 2006-2010 and is now estimated to be around 100 individuals. The population crash on Montserrat between 2009-2010 has also resulted in a near-extinction (decline believed to be over 90%) of the species with an initial count of 4 individuals, which was reduced to only 2 individuals after 2011. Therefore the Mountain Chicken continues to be listed as Critically Endangered because of the major population decline that occurred on Montserrat in the last ten years (2007-2017), which is certainly over the 80% threshold required for this category. Furthermore, the number of mature individuals in each subpopulation is less than 50 and continuing decline in the number of mature individuals is inferred from ongoing threats.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species occurs on the western side of Dominica and in the Centre Hills of northern Montserrat, having been unsuccessfully introduced on Jamaica and Puerto Rico. It has apparently been extirpated from Guadeloupe, Martinique, and St Kitts, and might once also have occurred on St Lucia and Antigua. Its range is now restricted on Dominica to an area of around 40 km² and to less than 1 km² on Montserrat. It is a relatively low-altitude species on Dominica, occurring from sea level up to (rarely) 400 m asl. On Montserrat it is present from sea level to 430 m asl. Its extent of occurrence (EOO) is 1,568 km2 and its area of occupancy (AOO) is approximately 10 km2.
Countries occurrence:
Dominica; Montserrat
Regionally extinct:
Guadeloupe; Martinique; Saint Kitts and Nevis
Additional data:
Estimated area of occupancy (AOO) - km2:10
Number of Locations:2
Upper elevation limit (metres):430
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This species might have been in decline on Montserrat since Cyclone Hugo in 1989 and the Soufriere volcanic eruption of 1995, but analysis of census data does not confirm this (J. Fa pers. comm.). However, since 1995 and until 2009, the population appeared to be stable from census surveys including both visual and aural encounter data (Hudson et al. 2016 - Scientific Reports). Historically it was found across the eastern Centre Hills of Montserrat however between 2009-2010, following the first detection of Bd on the island in 2009, the subpopulation underwent a catastrophic decline from thousands of individuals to just four (M. Hudson pers. comm. July 2017). Apart from three individuals recorded from Killikrankie in 2011, annual population monitoring transects have failed to detect them outside of the eastern slopes of the Centre Hills (Adams et al. 2014). The species is now only known from two individuals from one site (M. Hudson pers. comm. July 2017). 

On Dominica it was formerly abundant in suitable habitat (possibly until 2002), despite heavy exploitation for food (estimated annual harvest of 8,000-36,000 animals), but the population started to crash during 2002 with few individuals reported in 2003 (Hudson et al. 2016 - Scientific Reports). It was estimated that the subpopulation suffered a decline of greater than 85% during an 18 month period (2002-2004) due to chytridiomycosis. It was thought to be near extinction in 2006, and was not seen or recorded again until 2010 (M. Hudson pers. comm. August 2017). In the intervening years, surveys were sporadically done and a public campaign 'Have You Heard Me, Have You Seen Me' was running but there were no reports of the species (M. Hudson pers. comm. July 2017). Regular surveys, using standardised transects, began again in 2014 and are currently being carried out monthly (M. Hudson pers. comm. July 2017). The Dominican subpopulation is estimated to contain around 130 unique individuals (both adults and juveniles), captured since 2014, based on pit tag identification (M. Hudson pers. comm. July 2017).

The population is severely fragmented. It is known from 7-8 subpopulations, for which none of them contain over 30% of the whole population (adults and juveniles). The largest subpopulations are on Dominica and, of those, the two biggest subpopulations contain around 40-45% of the whole population and are separated by about 30 km (M. Hudson pers. comm. August 2017). While one or two of the smaller subpopulations may be connected, other are separated by a number of kilometres and it is unlikely that there is any dispersal or subsequent gene flow between them (M. Hudson pers. comm. August 2017).
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:132Continuing decline of mature individuals:Yes
Population severely fragmented:Yes
No. of subpopulations:7-8
All individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:This species lives in dense secondary vegetation which varies from new to old growth, ravines and hill forest. In Dominica, it is also found in plantations. It is terrestrial and nocturnal, hiding in burrows during the day in moist forest. It appears as though the animals are associated with certain soil types that allow the digging of nests. The eggs are laid in foam nests at the bottom of a burrow. The tadpoles (25-43 per nest) develop terrestrially in the nest, not in water. Both females and males guard the nest. The larvae feed on infertile eggs provided by the female. 

Adult individuals are typically 16-17 cm in length, although they can grow to lengths over 20 cm and exceed 1,000g in weight (Rosa et al. 2012 cited in Adams et al. 2014). While generation length has not been confirmed, it is estimated to be about three years which is based on the observed length of time this species takes to reach adult size (J. Dawson pers. comm. August 2017). Females tend to be larger than males, although both have similar colouration and patterning (Martin et al. 2007). Their diet consists of a wide range of insects, millipedes, spiders and land snails as well as vertebrates (tree frogs and snakes have been  reported as food items; Brooks 1982 in Martin et al. 2007).
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):3
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: It has been widely heavily used for food at a subsistence, national and international level. There is a hunting ban in place on this species on both Montserrat and Dominica, however it is possible some illegal hunting still occurs. It was previously the national dish on Dominica however, as of 2016, it has now been replaced to try and further deter the demand for this species for subsistence.

Threats [top]

Major Threat(s): Historically, this species was heavily consumed by humans and was prized for its meat (both subsistence and commercial use for tourists), which contributed to its decline. After the major population decline caused by chytridiomycosis in the early 2000s, a range-wide ban was put in place to stop the hunting of this species; however there may be some illegal hunting still taking place. Substantial habitat loss is also taking place over much of its range due to agriculture, human settlement and pressure from touristic development. On Montserrat, it is likely that subpopulations in the south of the island have been lost to lava flows from volcanic eruptions and subsequent ash fall. On Dominica, the habitat is under threat from expanding human settlements and agriculture (both subsistence and commercial farming), and other human development pressures (M. Hudson and J. Dawson pers. comm. July 2017).

The subpopulation on Dominica, where the species was once most abundant, declined catastrophically between 2002-2004, following a major confirmed outbreak of the fungal disease chytridiomycosis. There is now some evidence of individuals surviving with Bd infections, but further research is required to fully understand this and is currently ongoing (M. Hudson pers. comm. July 2017). Between 2009-2010, the subpopulation on Montserrat declined from thousands of individuals to just four following an outbreak of Bd. Two of the individuals have subsequently disappeared, although it was not confirmed whether Bd was the cause, and the two remaining individuals on Montserrat both have histories of surviving Bd infection (M. Hudson pers. comm. July 2017).

Conservation Actions [top]

Conservation Actions: Conservation Actions
This species occurs in Centre Hills protected area on Montserrat, but does not occur in any protected areas in Dominica. Fifty individuals were removed from the Montserrat subpopulation during the 2009-2010 decline for captive breeding in zoo institutions. An anti-fungal treatment was trialed on the remaining individuals, the world's first trial on a wild population, which was found to be successful in the short-term but not feasible in the long-term (Hudson et al. 2016 - Biological Conservation). The Mountain Chicken Recovery Programme (MCRP) was started in 2008, and currently consists of Durrell Wildlife Conservation Trust, Zoological Society of London (ZSL), Chester Zoo, Norden's Ark, Paignton Zoo and the governments of Montserrat and the Commonwealth of Dominica. The MCRP undertakes all conservation actions which are guided by a 20 year long-term recovery plan (Adams et al. 2014). There are also captive, biosecure populations at Durrell Wildlife Conservation Trust on Jersey (Montserrat origin), ZSL, Chester Zoo and Norden's Ark in Sweden, where captive breeding programmes are ongoing and there have been successful breeding attempts. No hunting of animals on Dominica has been allowed since 2003, and public awareness actions have taken place to inform the Dominican public of the magnitude of threat facing this species and to discourage illegal hunting. This species was also replaced as the national dish on Dominica in 2016 to reduce demand for it as subsistence. Between 2011-2014, a series of experimental reintroductions were conducted in order to understand the continued impact and seasonal dynamics of disease, and the analysis is ongoing (M. Hudson pers. comm. July 2017). There is ongoing monitoring on both remnant subpopulations on both islands, and there is ongoing public awareness activities such as International Mountain Chicken Day across its range, and educational outreach in schools to raise further awareness on the species (M. Hudson and J. Dawson pers. comm. July 2017). 

Conservation Needed
Habitat protection is urgently required on Dominica, and captive breeding and educational awareness efforts should remain ongoing (M. Hudson pers. comm. July 2017).

Research Needed
Further research is required on the disease mitigation which can inform subsequent conservation actions (M. Hudson and J. Dawson pers. comm. July 2017).

Citation: IUCN SSC Amphibian Specialist Group. 2017. Leptodactylus fallax. The IUCN Red List of Threatened Species 2017: e.T57125A3055585. . Downloaded on 14 December 2017.
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