Leptodactylus fallax
Encyclopedia
Leptodactylus fallax, commonly known as the Giant Ditch Frog, is a species of frog
that is native to the Caribbean
islands of Dominica
and Montserrat
. The population has declined 80% in the last ten years and this species is now critically endangered
. In 2004 it was estimated that the population possibly was as low as 8000 individuals. One of the main threats is human consumption. The fungal disease chytridiomycosis
has also had a dramatic effect on the population. Locally, it is known as the Mountain Chicken for its large size and the fact it is hunted for food.
. The body is robust, with a large head and well-muscled legs. The male mountain chicken may be distinguished from the female by its smaller size, and by the black 'spur' on each of its thumbs, which are used to clasp the female during amplexus
(the mating embrace).
, Martinique
, Saint Kitts
and Nevis
, but is now extinct there, and may have also inhabited Saint Lucia
and Antigua
. The species was also unsuccessfully reintroduced to Jamaica and Puerto Rico. Today, the mountain chicken is largely restricted to the Centre Hills of northern Montserrat, having been lost from much of the rest of the island by recent volcanic eruptions, and on the western side of Dominica. It is also found on the eastern side of Dominica, but the species origin there is unclear and it may have been introduced to the area.
The Giant Ditch Frog is found in a variety of moist habitats, including dense secondary forest
and scrub, hillside plantations, palm groves in river valleys, ravines and flooded forest. It is most commonly found near streams and springs, and is rarely found in grasslands. On Dominica it is most abundant at lower altitudes, although it occurs up to 400 metres, and is found up to 430 metres on Montserrat.
and nocturnal.
A sit-and-wait predator with a voracious appetite, this gluttonous frog consumes almost anything that can be swallowed whole. It is well camouflaged against its habitat and remains still for long periods of time, before ambushing its prey, usually at night. Its diet is highly varied, but it is thought to be strictly carnivorous, largely consuming crickets, although millipedes, insects, crustaceans, and even small vertebrates, such as other frogs, snakes and small mammals, are all eaten. During the day the Giant Ditch Frog resides in burrows which it digs into moist soil.
The Giant Ditch Frog has a highly unusual method of reproduction, as unlike most other amphibians which breed in water, this frog breeds in underground burrows around 50 centimetres deep. The breeding season starts towards the end of the dry season, usually in April when there are heavy seasonal showers, and continues to August or September. At the start of this period, the male frogs compete to gain access to preferred nesting sites by wrestling and making loud 'whooping' calls from forest paths and undergrowth clearings. The winning male occupies a nesting burrow and emits 'trilling barks' to attract a female mate. Once a breeding pair is formed, the male and female engage in amplexus, and the female is stimulated to release a fluid, which the male makes into a foam with rapid paddles of its hind legs. Once the nest is built, which takes 9 to 14 hours, the male leaves the burrow to defend it from intruders, while the female lays the eggs. After the larvae
have hatched, the female lays up to as many as 25,000 unfertilised eggs upon which the larvae feed. While the young froglets develop, which takes around 45 days, the female continuously renews the foam, only leaving the nest to feed. Eventually 26 to 43 froglets emerge from the nest, with the timing of this coinciding with the onset of the wet season, when there is an abundance of food. The Giant Ditch Frog reaches maturity at around 3 years, and has a lifespan of approximately 12 years. Mature females only produce one brood per season, but male frogs may father the offspring of more than one female.
The Giant Ditch Frog has also lost huge areas of its habitat to agriculture, tourist developments, human settlements and, on Montserrat, volcanic eruptions. On Dominica, the species is largely confined to coastal areas where there is great demand for land for construction, industry and farming, while on Montserrat, volcanic activity since 1995 has exterminated all populations outside of the Centre Hills. Human encroachment upon the species' habitat has also brought it into contact with a range of pollutants, including the highly toxic herbicide Gramazone, which is known to kill birds and mammals. Predation from introduced mammals, such as feral cats, dogs, pigs and opossums, is also a relatively new threat to the species on Dominica.
Perhaps the greatest, and least understood, threat to the Giant Ditch Frog today is the deadly chytridiomycosis
fungus. This disease, which has wiped out many amphibian populations across the globe, established on Dominica in 2002, and frog populations on the island have since rapidly declined. The fungus was recently introduced to Montserrat via frogs on imported banana leaves, and has spread southwards from northern ports along river systems. There is now thought to be only two disease-free Giant Ditch Frog populations remaining.
Following the catastrophic volcanic eruptions on Montserrat, it became clear that dedicated conservation measures were needed if the Giant Ditch Frog was to be saved from extinction. In July 1999, the Durrell Wildlife Trust took six male and three female frogs to Jersey Zoo as part of a captive breeding study. Additional frogs have since been taken from disease-free areas, and the species has readily bred in captivity, with a number of other zoos achieving further breeding success. These captive frogs now form the basis of a safety-net population should the species become extinct in the wild. In addition, since January 1998, the Montserrat Forestry and Environment Division, in partnership with Fauna and Flora International, have been monitoring the species' population.
Hunting of the Giant Ditch Frog was banned on Dominica in the late 1990s, although a three month open season was declared at the end of 2001, and hunting was not fully prohibited until 2003. Public awareness programmes have also been implemented to inform the Dominican public of the threats the mountain chicken faces and to try to discourage hunting.
In February 2010, volcanic activity from Soufrière Hills
on Montserrat resulted in ash covering large parts of the frog's habitat on that island, further endangering the species.
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
that is native to the Caribbean
Caribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...
islands of Dominica
Dominica
Dominica , officially the Commonwealth of Dominica, is an island nation in the Lesser Antilles region of the Caribbean Sea, south-southeast of Guadeloupe and northwest of Martinique. Its size is and the highest point in the country is Morne Diablotins, which has an elevation of . The Commonwealth...
and Montserrat
Montserrat
Montserrat is a British overseas territory located in the Leeward Islands, part of the chain of islands called the Lesser Antilles in the West Indies. This island measures approximately long and wide, giving of coastline...
. The population has declined 80% in the last ten years and this species is now critically endangered
Critically endangered
Version 2010.3 of the IUCN Red List of Threatened Species identified 3744 Critically Endangered species, subspecies and varieties, stocks and subpopulations.Critically Endangered by kingdom:*1993 Animalia*2 Fungi*1745 Plantae*4 Protista-References:...
. In 2004 it was estimated that the population possibly was as low as 8000 individuals. One of the main threats is human consumption. The fungal disease chytridiomycosis
Chytridiomycosis
Chytridiomycosis is an infectious disease of amphibians, caused by the chytrid Batrachochytrium dendrobatidis, a non-hyphal zoosporic fungus. Chytridiomycosis has been linked to dramatic population declines or even extinctions of amphibian species in western North America, Central America, South...
has also had a dramatic effect on the population. Locally, it is known as the Mountain Chicken for its large size and the fact it is hunted for food.
Description
The Giant Ditch Frog is one of the largest frogs in the world, with adult females growing up to 21 centimetres long. It is highly variable in colour, with the upperparts varying from a uniform chestnut-brown to being barred or even spotted. The colour becomes more orange-yellow on the sides of the body, and pale yellow on the underparts. A black line runs from the snout to the angle of the mouth, and the upper-legs often have broad banding. The mountain chicken also has a distinctive, dark-outlined fold from the back of the head to the groin, and large, conspicuous eyes with dark pupils and a golden irisIris (anatomy)
The iris is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupils and thus the amount of light reaching the retina. "Eye color" is the color of the iris, which can be green, blue, or brown. In some cases it can be hazel , grey, violet, or even pink...
. The body is robust, with a large head and well-muscled legs. The male mountain chicken may be distinguished from the female by its smaller size, and by the black 'spur' on each of its thumbs, which are used to clasp the female during amplexus
Amplexus
Amplexus is a form of pseudocopulation in which a male amphibian grasps a female with his front legs as part of the mating process...
(the mating embrace).
Distribution and habitat
The Giant Ditch Frog was once found on many of the eastern Caribbean islands, but is now restricted to just Dominica and Montserrat. It once occurred for certain on GuadeloupeGuadeloupe
Guadeloupe is an archipelago located in the Leeward Islands, in the Lesser Antilles, with a land area of 1,628 square kilometres and a population of 400,000. It is the first overseas region of France, consisting of a single overseas department. As with the other overseas departments, Guadeloupe...
, Martinique
Martinique
Martinique is an island in the eastern Caribbean Sea, with a land area of . Like Guadeloupe, it is an overseas region of France, consisting of a single overseas department. To the northwest lies Dominica, to the south St Lucia, and to the southeast Barbados...
, Saint Kitts
Saint Kitts
Saint Kitts Saint Kitts Saint Kitts (also known more formally as Saint Christopher Island (Saint-Christophe in French) is an island in the West Indies. The west side of the island borders the Caribbean Sea, and the eastern coast faces the Atlantic Ocean...
and Nevis
Nevis
Nevis is an island in the Caribbean Sea, located near the northern end of the Lesser Antilles archipelago, about 350 km east-southeast of Puerto Rico and 80 km west of Antigua. The 93 km² island is part of the inner arc of the Leeward Islands chain of the West Indies...
, but is now extinct there, and may have also inhabited Saint Lucia
Saint Lucia
Saint Lucia is an island country in the eastern Caribbean Sea on the boundary with the Atlantic Ocean. Part of the Lesser Antilles, it is located north/northeast of the island of Saint Vincent, northwest of Barbados and south of Martinique. It covers a land area of 620 km2 and has an...
and Antigua
Antigua
Antigua , also known as Waladli, is an island in the West Indies, in the Leeward Islands in the Caribbean region, the main island of the country of Antigua and Barbuda. Antigua means "ancient" in Spanish and was named by Christopher Columbus after an icon in Seville Cathedral, Santa Maria de la...
. The species was also unsuccessfully reintroduced to Jamaica and Puerto Rico. Today, the mountain chicken is largely restricted to the Centre Hills of northern Montserrat, having been lost from much of the rest of the island by recent volcanic eruptions, and on the western side of Dominica. It is also found on the eastern side of Dominica, but the species origin there is unclear and it may have been introduced to the area.
The Giant Ditch Frog is found in a variety of moist habitats, including dense secondary forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
and scrub, hillside plantations, palm groves in river valleys, ravines and flooded forest. It is most commonly found near streams and springs, and is rarely found in grasslands. On Dominica it is most abundant at lower altitudes, although it occurs up to 400 metres, and is found up to 430 metres on Montserrat.
Behavior and ecology
The Giant Ditch Frog is terrestrialTerrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
and nocturnal.
A sit-and-wait predator with a voracious appetite, this gluttonous frog consumes almost anything that can be swallowed whole. It is well camouflaged against its habitat and remains still for long periods of time, before ambushing its prey, usually at night. Its diet is highly varied, but it is thought to be strictly carnivorous, largely consuming crickets, although millipedes, insects, crustaceans, and even small vertebrates, such as other frogs, snakes and small mammals, are all eaten. During the day the Giant Ditch Frog resides in burrows which it digs into moist soil.
The Giant Ditch Frog has a highly unusual method of reproduction, as unlike most other amphibians which breed in water, this frog breeds in underground burrows around 50 centimetres deep. The breeding season starts towards the end of the dry season, usually in April when there are heavy seasonal showers, and continues to August or September. At the start of this period, the male frogs compete to gain access to preferred nesting sites by wrestling and making loud 'whooping' calls from forest paths and undergrowth clearings. The winning male occupies a nesting burrow and emits 'trilling barks' to attract a female mate. Once a breeding pair is formed, the male and female engage in amplexus, and the female is stimulated to release a fluid, which the male makes into a foam with rapid paddles of its hind legs. Once the nest is built, which takes 9 to 14 hours, the male leaves the burrow to defend it from intruders, while the female lays the eggs. After the larvae
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...
have hatched, the female lays up to as many as 25,000 unfertilised eggs upon which the larvae feed. While the young froglets develop, which takes around 45 days, the female continuously renews the foam, only leaving the nest to feed. Eventually 26 to 43 froglets emerge from the nest, with the timing of this coinciding with the onset of the wet season, when there is an abundance of food. The Giant Ditch Frog reaches maturity at around 3 years, and has a lifespan of approximately 12 years. Mature females only produce one brood per season, but male frogs may father the offspring of more than one female.
Threats and conservation
A victim of hunting, disease, natural disasters and habitat loss, the Giant Ditch Frog population has recently undergone catastrophic declines, estimated at around 80 percent since 1995. On Dominica, this critically endangered frog is favoured for its meaty legs, which are cooked in traditional West Indian dishes, and it is in fact the country's national dish. Annual harvests were thought to be taking between 8,000 and 36,000 animals before a ban on hunting was introduced and, as a result of this exploitation, the population on the island is thought to be near extinction. The Giant Ditch Frog is particularly vulnerable to such harvesting as it has a relatively small brood size, limiting its ability to recover from heavy losses, while the removal of breeding females is particularly damaging, as the tadpoles are dependant upon the females for food and moisture. The species' large size, loud calls and tendency to sit in the open also makes it a particularly easy target for hunters.The Giant Ditch Frog has also lost huge areas of its habitat to agriculture, tourist developments, human settlements and, on Montserrat, volcanic eruptions. On Dominica, the species is largely confined to coastal areas where there is great demand for land for construction, industry and farming, while on Montserrat, volcanic activity since 1995 has exterminated all populations outside of the Centre Hills. Human encroachment upon the species' habitat has also brought it into contact with a range of pollutants, including the highly toxic herbicide Gramazone, which is known to kill birds and mammals. Predation from introduced mammals, such as feral cats, dogs, pigs and opossums, is also a relatively new threat to the species on Dominica.
Perhaps the greatest, and least understood, threat to the Giant Ditch Frog today is the deadly chytridiomycosis
Chytridiomycosis
Chytridiomycosis is an infectious disease of amphibians, caused by the chytrid Batrachochytrium dendrobatidis, a non-hyphal zoosporic fungus. Chytridiomycosis has been linked to dramatic population declines or even extinctions of amphibian species in western North America, Central America, South...
fungus. This disease, which has wiped out many amphibian populations across the globe, established on Dominica in 2002, and frog populations on the island have since rapidly declined. The fungus was recently introduced to Montserrat via frogs on imported banana leaves, and has spread southwards from northern ports along river systems. There is now thought to be only two disease-free Giant Ditch Frog populations remaining.
Following the catastrophic volcanic eruptions on Montserrat, it became clear that dedicated conservation measures were needed if the Giant Ditch Frog was to be saved from extinction. In July 1999, the Durrell Wildlife Trust took six male and three female frogs to Jersey Zoo as part of a captive breeding study. Additional frogs have since been taken from disease-free areas, and the species has readily bred in captivity, with a number of other zoos achieving further breeding success. These captive frogs now form the basis of a safety-net population should the species become extinct in the wild. In addition, since January 1998, the Montserrat Forestry and Environment Division, in partnership with Fauna and Flora International, have been monitoring the species' population.
Hunting of the Giant Ditch Frog was banned on Dominica in the late 1990s, although a three month open season was declared at the end of 2001, and hunting was not fully prohibited until 2003. Public awareness programmes have also been implemented to inform the Dominican public of the threats the mountain chicken faces and to try to discourage hunting.
In February 2010, volcanic activity from Soufrière Hills
Soufrière Hills
The Soufrière Hills volcano is an active complex stratovolcano with many lava domes forming its summit on the Caribbean island of Montserrat. After a long period of dormancy, it became active in 1995, and has continued to erupt ever since...
on Montserrat resulted in ash covering large parts of the frog's habitat on that island, further endangering the species.
External links
- Leptodactylus fallax (Mountain Chicken; Giant Ditch Frog; Crapaud), AmphibiaWeb
- Leptodactylus fallax entry at the IUCN Red List
- Giant Ditch Frog (Leptodactylus fallax), World Association of Zoos and Aquariums entry
- Mountain Chicken at The Ark Gallery