Category Archives: Amphibian

Mountain Chicken (Leptodactylus fallax)

Mountain-chicken-side-view

  • Name: Mountain Chicken
  • Latin: Leptodactylus fallax
  • Classification: Amphibian
  • Origin: South America
  • Lifespan: 12 years
  • AKA: Giant ditch frog

Taxonomy

  • Kingdom: Animalia (Animals)
  • Phylum: Chordata (Vertebrates)
  • Class: Amphibia (Amphibians)
  • Order: Anura (Frog)
  • Family: Leptodactylidae (Diverged during the Cenozoic era)
  • Genus: Leptodactylus (‘Slender’ ‘Finger’)
  • Species: Leptodactylus fallax (Mountain Chicken)

Appearance

  • Length: Up to 21cm (8.2 inches)
  • Weight: Up to 700g (1.5lb)

The mountain chicken is variable in colour. The upperparts are chestnut brown, barred or spotted with black) which fades to yellow-orange along the sides of the body, and then to pale yellow on the underparts. It has black lines running from the snout to the edges of the mouth and the upper legs have broad banding. The mountain chicken is also equipped with large conspicuous eyes, with dark pupils and golden irises. They have a robust body with a large head and well-muscled legs. They are sexually dimorphic as the males are smaller in size than the females, and have a spur on each thumb, which are used during the mating season.

Relatives

This slideshow requires JavaScript.

  • Hispaniola Yellow Tree Frog (Osteopilus pulchrilineatus) -VULNERABLE-
  • Horned Frog (Caratophrus cornuta) -LEAST CONCERN-
  • Pumpkin Toadlet (Brochycephalus ephippium) -LEAST CONCERN-
  • Marbled Reed Frog (Hyperolius marmoratus) -LEAST CONCERN-

Habitat & Distribution

The mountain chicken was once found on many Caribbean islands but are now only present on Dominica and Montserrat. Most of its former range has been lost to this frog mainly due to volcanic eruptions. They occupy a variety of habitats including secondary forest and scrub. They are also found inhabiting hillside plantations, palm groves in river valleys, ravines and flooded forests. The mountain chicken is most commonly found near streams and spring and occasionally (rarely) found in grasslands. In Dominica, they are most abundant at lower altitudes and occur up to 400m, on Montserrat, up to 430m.

Map of distribution of the mountain chicken
Map of distribution of the mountain chicken

Diet

The mountain chicken will eat almost anything that can be swallowed whole and usually feed at night. They are strictly carnivorous and have a very varied diet including snakes, fish, insects, crustaceans and even other small frogs. They are a sit-and-wait predators and will remain still for long periods of time before ambushing its prey.

Reproduction

Unusually for an amphibian, the mountain chicken breeds in underground burrows, around 50cm deep. The breeding season will start in around April (during heavy seasonal showers) to around August to September. The males will compete for nesting sites by wrestling and making loud ‘whooping’ calls from forest paths and undergrowth clearings. They will also emit ‘trilling barks’ to attract a females when in control of a nesting site.

When together, the male and female will engage in amplexus, a process by which the female is stimulated to release a fluid. The male turns this fluid into a foam by rapidly kicking his back legs. This foam is then used as the nest for the developing tadpoles. The nest is built in 9-14 hours.

After mating, the male will leave the nest to defend it from intruders and the female will remain inside the lay the eggs. Once hatched, the female will feed the tadpoles on around 25,000 of her own unfertilised eggs. The young take around 45 days to develop during which time the female will constantly renew the foam. The mother will only leave the nest to feed while the tadpoles are developing.

With the onset of the wet season and the abundance of food, around 26-43 froglets will emerge from the nest. The young reach maturity around 3 years of age. The females will only mother one brood per season while the males may father the offspring of more than one female per season. There is a high degree of maternal care with this species.

Mountain chicken tadpoles
Mountain chicken tadpoles

Adaptations

  1. Males have black ‘spurs’ on each of their thumbs which are used to hold the female in place during amplexus (the mating embrace).
  2. The mountain chicken is a well camouflaged ambush predator and can remain still for prolonged periods of time at night.

Threats

The mountain chicken seems to have an endless list of threats including hunting, disease, natural disasters, habitat loss, and predation by introduced species and exposure to deadly pollutants. The total population of this giant frog has declined by 80% since 1995.

On the island of Dominica, the mountain chicken is hunted for food and is the country’s national dish. 8,000 – 36,000 individuals can be killed in annual hunts leading to a ban on hunting of the species being introduced in the late 1990’s. Due to the small brood size of the mountain chicken, they are particularly vulnerable to overharvesting as this limits their ability to recover from heavy losses. The removal of females is also damaging to the species as the tadpoles are dependent on the mother for food and moisture. Their large size, loud calls and tendency to sit out in the open also makes them easy targets for hunters.

The mountain chicken has lost huge areas of habitat due to agriculture, tourist developments, and human settlements and in Montserrat, volcanic eruptions. This volcanic activity on the island has wiped out all populations outside of the Central hills. On Dominica, populations of this amphibian species are largely confined to coastal areas, where there is great demand for land for construction, industry and farming. This high level of human encroachment has also brought this delicate species into contact with deadly pollutants including the highly toxic herbicide, Gramazone which has been known to kill large numbers of birds and mammals. The mountain chicken is also predated by introduced species including feral cats, dogs, pigs, rats and opossums.

The deadliest and least understood threat to the mountain chicken is the fungal disease, chytridiomycosis, which had wiped out countless numbers of amphibian populations throughout the globe. It first became established in Dominica in 2002 and frog populations on the island declined by around 80% within 2 years. The total population of mountain chicken is now thought to be so small that there may not be enough individuals to ensure the survival of the species on the island. The fungus was introduced to the nearby island of Montserrat in 2009, presumably via infected frogs that were hiding in shipments of fruit and vegetables. Since then, huge declines of 80-90% occurred. By July 2009, the last remaining healthy population on Montserrat of the mountain chicken had succumbed to the disease.

Conservation

  • IUCN Status: Critically endangered

Hunting of the mountain chicken was banned in the late 1990’s due to the 80% drop in numbers since 1995, however, a 3 month open season was declared late in 2001 and hunting was not fully prohibited until 2003. Public awareness programmes have since been put into place to inform the Dominican public about the threats facing mountain chickens and to try to discourage hunting.

In July 1999, the Durrell Wildlife Trust (DWT) took 6 males and 3 females to Jersey Zoo to create a captive breeding study, additional frogs were also taken from disease free areas in later years. The species readily breeds in captivity and cooperation with other zoos has achieved further breeding success. These captive bred frogs now form the basis for an insurance population should the species become extinct in the wild. Since January 1998, the Montserrat Forestry and Environment Division (in partnership with Fauna and Flora International) have been monitoring the wild population of mountain chickens.

The ever present threat of chytridiomycosis has now taken priority over the other conservation efforts in place for the mountain chicken due to the enormity of its threat, such as habitat protection and control of invasive predators. When the disease was first discovered in Montserrat in 2009, 50 frogs were immediately flown from the island and entered into bio-secure breeding programme already in place. A combination of field studies, capacity building and species reintroduction are used to ensure the survival of the mountain chicken population on Montserrat along with field trials using anti-fungal treatment in a bid of fight against the deadly chytrid fungus disease. These frogs are breeding well in captivity and successful reintroduction have taken place in 2011 and 2012.

On Dominica, a captive breeding facility has been built and is used to analyses frog skin swabs to look for the presence of chytridiomycosis. Invertebrate prey stocks have also been established within the facility to satisfy the endless appetite of the captive frogs. In 2010, 5 frogs were captures and placed into the facility and later in the year, a juvenile was found indicating that the wild population on Dominica are also breeding. The mountain chickens bred in the facility will eventually be released back into the wild to replenish the population on the island. A team of dedicated scientists are currently working to ensure the survival of the mountain chicken on both Dominica and Montserrat.

Fun Facts

  • Male: Male frog
  • Female: Female frog
  • Young: Tadpole
  • Group: Army, Chorus, Colony
  • The mountain chicken is one of the world’s largest living frog species.
  • It is named after the taste of its meat.
  • The female exhibits high levels of maternal care, unusual for any frog species.

References

ARKive (2014) Mountain Chicken (Leptodactylus fallax) [Online] Available at: http://www.arkive.org/mountain-chicken/leptodactylus-fallax/ [Accessed: 11 April 2014]

BBC (2014) Mountain Chicken [Online] Available at: http://www.bbc.co.uk/nature/life/Leptodactylus_fallax [Accessed: 11 April 2014]

Saving the Mountain Chicken (2013) The Species [Online] Available at: http://www.mountainchicken.org/the-species/ [Accessed: 7 May 2014]

Wikipedia (2014) Leptodactylus fallax [Online] Available at: http://en.wikipedia.org/wiki/Leptodactylus_fallax [Accessed: 11 April 2014]

Drawin’s Frog (Rhinoderma darwinii)

Darwins-frog-side-profile

  • Name: Darwin’s Frog
  • Latin: Rhinoderma darwinii
  • Classification: Amphibian
  • Origin: Chile
  • Lifespan: Up to 16 years

Taxonomy

Kingdom: Animalia (Animals)
Phylum: Chordata (Vertebrates)
Class: Amphibia (Amphibians)
Order: Anura (Frogs)
Family: Rhinodermatidae (Native to South America)
Genus: Rhinoderma (Native to South America)
Species: Rhinoderma Darwinii (Darwin’s Frog)

Apperance

Length: 2.5-3.5cm
Weight: 2 grams

The Darwin’s frog is covered in moist skin which is usually brown or green. Its front feet are not webbed like other frogs but the toes on its back feet sometimes are. The male of this species has an enlarged vocal sac in which it rears its young.

Relative

This slideshow requires JavaScript.

  • African clawed frog (Xenopus laevis) -LEAST CONCERN-
  • Mexican tree frog (Smilisca baudinii) -LEAST CONCERN-
  • Cane toad (Rhinella marina) -LEAST CONCERN-
  • Pig frog (Rana grylio) -LEAST CONCERN-

Habitat & Distribution

The Darwin’s frog tends to stay in areas near cool and shallow creeks or streams. It can be found in Latin American countries such as Chile and Argentina.

Map of distribution of the Darwin's frog
Map of distribution of the Darwin’s frog

Diet

The diet of the Darwin’s frog consists mainly of insects and other small invertebrate. It catches its prey by remaining motionless, waiting for unsuspecting bugs to crawl or fly past, the frog then lunges forward, catching the prey in its mouth.

Behaviour

The Darwin’s frog is most active during the day, spending many hours basking in the warm sunlight while remaining camouflaged in the surrounding leaf litter.

It also spends its day waiting for prey. It hides among the damp leaves and waits patiently for insects to wander by, it then leaps forward devouring the prey.

When threatened, the Darwin’s frog will play dead by rolling over onto its back until the danger has passed. Sometimes, it will leap into a nearby stream and float on the water on its back, again feigning death.

When rearing young, the male Darwin’s frog will take a spawn of newly hatched tadpoles into its mouth and move them into its enlarged vocal sac, which will temporarily be used as a nursery. The tadpoles are sustained by eating the remainders of their eggs and by nutrient-rich secretions by the adult. When they have grown into froglets, they are spat out from the vocal sac. A male Darwin’s frog can look after up to 19 froglets at one time.

Reproduction

The male Darwin’s frog sings throughout the breeding season, which lasts from November through to March, to attract a mate. Once a mate is found, the male will lead the female to a sheltered area where courtship and egg laying take place. The female will then leave but the male will remain with the eggs, guarding them while they develop.

After about 20 days, the tadpoles will begin to wriggle inside their shells. The male then uses its tongue to pick them up and move them to its enlarges vocal sac, which will act as a nursery for the time being. The tadpoles attain sustenance by eating the remains of its eggs and through the nutrient-rich secretions provided by the adult.

Once the tadpoles have grown to a length of 1cm, it would have grown two pairs of legs and its tail would be reduced to a stump, they are then spat out by the male. Up to 19 can be cared for at one time by an adult male.

Juvenile Darwin's frog
Juvenile Darwin’s frog

Adaptations

  1. The male Darwin’s frog raises his young in his mouth. He holds them as eggs and when they hatch, he transports them to a water source.
  2. The Darwin’s frog has excellent camouflage as it has evolved to resemble a leaf. It blends in remarkably well with the leaf litter in which it lives. This reduces the risk of predation.
  3. Like other frogs, the Darwin’s frog has webbed feet that help it manoeuvre through water.
  4. The Darwin’s frog has eyes and nostrils on the top of its head allowing it to stay almost submerged underwater.

Threats

There is a worrying decline in the number of Darwin’s frogs throughout the world, especially in Chile where some populations are disappearing entirely. This is because of deforestation and the replacement of their native trees with exotic species.

In other regions, the causes are unknown, but it maybe be down to climate change and ultraviolet radiation. This could also be what is contributing to the worldwide decline in amphibians.

Conservation

IUCN Status: Vulnerable

Throughout the Darwin’s frogs range, there are a number of protected areas helping to preserve its habitat. However, these need to be improved and expanded, especially in sites near the north of its territory.

Fun Facts

Male: Male frog
Female: Female frog
Young: Tadpole

Group: Army

The Darwin’s frog is named after Charles Darwin, who discovered it during his world voyage.
The males call is small and bell-like, despite its large vocal sac.
It is also known as the Darwin’s toad and the Cowboy frog.