The purple frog is the sole representative of an ancient lineage of frogs that has been evolving independently for over 130 million years. Its closest relatives are the Seychelles frogs, the ancestors of which were present on the Indo-Madagascan land mass with the purple frog’s predecessors when it broke away from the supercontinent of Gondwana 120 million years ago. Formally discovered in 2003, the purple frog spends most of the year underground, surfacing only to breed during the monsoon. It was the first new family of frogs to be discovered since 1926. This species is threatened by ongoing forest loss for coffee, cardamom and ginger plantations.
Evolutionary Distinctiveness
Order: Anura
Family: Sooglossidae
The purple frog is described as a “living fossil” and is the only surviving member of an ancient amphibian family called the Nasikabatrachidae. Up until around 120 million years ago in the early Cretaceous period, India was joined to the eastern part of the ancient southern supercontinent Gonwana, which subsequently split apart into Australia, Antarctica, India, Madagascar and the Seychelles over millenia of movement of the earth’s plates. The closest relatives of the purple frog are four tiny frog species found in the Seychelles in the Sooglossidae family. In their phylogenetic study of the purple frog in 2003, S. D. Biju and Franky Bossuyt (respectively of the Tropical Botanic Garden and Research Institute, Kerala and the Free University of Brussels) reported that the origin of the Sooglossidae/Nasikabatrachidae lineage occurred around 182 million years ago. It is thought that these two amphibian lineages diverged an estimated 134 million years ago form a common ancestor that inhabited Gondwana prior to the break up of this land mass. These frogs were therefore sharing the earth with the dinosaurs for 70 million years and started to evolve independently before the common ancestor of the elephant and the human.The ancestors of the Seychelles frogs and the purple frog were present on the Indo-Madagascan land mass as it broke away from Gondwana and drifted through the movement of the earth’s plates for over 50 million years. Around 65 million years ago the Cretaceous/Tertiary boundary, the Seychelles split away from India and the ensuring plate movements separated the purple frogs from their closest relatives by around 2,500 km of Indian Ocean. The purple frog is therefore the only representative of a lineage that has been evolving independently for over 130 million years, has survived the break up of a continent and the extinction of the dinosaurs.
Order: Anura
Family: Sooglossidae
The purple frog is described as a “living fossil” and is the only surviving member of an ancient amphibian family called the Nasikabatrachidae. Up until around 120 million years ago in the early Cretaceous period, India was joined to the eastern part of the ancient southern supercontinent Gonwana, which subsequently split apart into Australia, Antarctica, India, Madagascar and the Seychelles over millenia of movement of the earth’s plates. The closest relatives of the purple frog are four tiny frog species found in the Seychelles in the Sooglossidae family. In their phylogenetic study of the purple frog in 2003, S. D. Biju and Franky Bossuyt (respectively of the Tropical Botanic Garden and Research Institute, Kerala and the Free University of Brussels) reported that the origin of the Sooglossidae/Nasikabatrachidae lineage occurred around 182 million years ago. It is thought that these two amphibian lineages diverged an estimated 134 million years ago form a common ancestor that inhabited Gondwana prior to the break up of this land mass. These frogs were therefore sharing the earth with the dinosaurs for 70 million years and started to evolve independently before the common ancestor of the elephant and the human.The ancestors of the Seychelles frogs and the purple frog were present on the Indo-Madagascan land mass as it broke away from Gondwana and drifted through the movement of the earth’s plates for over 50 million years. Around 65 million years ago the Cretaceous/Tertiary boundary, the Seychelles split away from India and the ensuring plate movements separated the purple frogs from their closest relatives by around 2,500 km of Indian Ocean. The purple frog is therefore the only representative of a lineage that has been evolving independently for over 130 million years, has survived the break up of a continent and the extinction of the dinosaurs.
Description
The purple frog is a relatively large burrowing frog with a distinct, bloated or plump appearance. The head is conical and short in comparison with the rest of the body, and has a white, protruding snout. The fore- and hind-limbs are short, ending in partially webbed feet with rounded toes and each hind foot possesses a large, white wart-like growth, most likely used for digging. The eyes are small, rounded, and have a horizontal pupil. This species has smooth, dark purple skin that fades into grey along the stomach. Purple frogs reach a total length of about 7 cm.
Ecology
The purple frog spends most of the year underground, surfacing only for about two weeks during the monsoon season in order to mate. It lives 1.3-3.7m below ground and the frog's reclusive fossorial (digging or burrowing) lifestyle is what caused the species to escape earlier detection by biologists. It comes to the surface for a few weeks a year to breed in temporary and permanent ponds and ditches. During the breeding season, local people reported seeing purple frogs in the vicinity of water pools or at the sides of the swelling streams in pairs clasping each other, especially at the beginning of the monsoon season. During mating, the male clasps the female from behind just above the legs in a behaviour termed “inguinal amplexus”. The bloated shape of both male and female purple frogs, and the smaller size of the male, may mean that males partially glue themselves onto females using sticky skin secretions, as occurs in “short-headed frogs” in the family Brevicipitidae. Eggs are laid in water that hatch into tadpoles, often in ponds close to streams.The diet of the purple frog predominantly consists of termites, and this species has a narrow mouth with a small gape, preventing it from catching and consuming larger prey items. Its strong head and pointed snout permits it to penetrate underground termite niches, and a fluted tongue may allow this species to suck up its prey from subterranean burrows. With its poor vision, this frog presumably depends on smell and tactile cues to detect and locate prey. It also consumes ants and small worms.The burrowing and mound-building activities of termites increase the rate of percolation of rainwater and aeration of both the top and subsoil keeping the underground soil temperature low and the moisture content high. It may therefore benefit burrowing amphibians like the purple frog to live in close proximity to termite colonies, which improve the quality of their habitat as well as providing a food source. In India, the purple frog from the southern Western Ghats may be the only known amphibian species that is a fully underground forager. All other burrowing frogs are either open burrow feeders or diurnal burrow dwellers that are open ground feeders in the night. Purple frogs require damp, loose soil to borrow into, and may dig themselves fully into appropriate soil within 3 to 5 minutes. When placed on hard ground, pebbled- or gravel-strewn soil, or areas with a thick mat of weeds, purple frogs are unable to borrow effectively and go in search of cover. The hind limbs have strong feet with wart-like structures that are primarily used for digging. This frog burrows downwards using its hind limbs like spades, throwing the soil over its back. They rest underground in a horizontal position with the limbs tucked under the body, although they do not remain idle underneath the soil, especially when foraging for their prey.
Habitat
The first purple frog was officially discovered in disturbed secondary forest near a cardamom plantation. It has also been found in disturbed secondary forest contiguous with montane evergreen forest. It presumably occurs in undisturbed forest as well and apparently does not survive in open, completely clear habitats. This species requires fairly loose, damp, well-aerated soil, especially in close proximity to termite colonies.
The purple frog is a relatively large burrowing frog with a distinct, bloated or plump appearance. The head is conical and short in comparison with the rest of the body, and has a white, protruding snout. The fore- and hind-limbs are short, ending in partially webbed feet with rounded toes and each hind foot possesses a large, white wart-like growth, most likely used for digging. The eyes are small, rounded, and have a horizontal pupil. This species has smooth, dark purple skin that fades into grey along the stomach. Purple frogs reach a total length of about 7 cm.
Ecology
The purple frog spends most of the year underground, surfacing only for about two weeks during the monsoon season in order to mate. It lives 1.3-3.7m below ground and the frog's reclusive fossorial (digging or burrowing) lifestyle is what caused the species to escape earlier detection by biologists. It comes to the surface for a few weeks a year to breed in temporary and permanent ponds and ditches. During the breeding season, local people reported seeing purple frogs in the vicinity of water pools or at the sides of the swelling streams in pairs clasping each other, especially at the beginning of the monsoon season. During mating, the male clasps the female from behind just above the legs in a behaviour termed “inguinal amplexus”. The bloated shape of both male and female purple frogs, and the smaller size of the male, may mean that males partially glue themselves onto females using sticky skin secretions, as occurs in “short-headed frogs” in the family Brevicipitidae. Eggs are laid in water that hatch into tadpoles, often in ponds close to streams.The diet of the purple frog predominantly consists of termites, and this species has a narrow mouth with a small gape, preventing it from catching and consuming larger prey items. Its strong head and pointed snout permits it to penetrate underground termite niches, and a fluted tongue may allow this species to suck up its prey from subterranean burrows. With its poor vision, this frog presumably depends on smell and tactile cues to detect and locate prey. It also consumes ants and small worms.The burrowing and mound-building activities of termites increase the rate of percolation of rainwater and aeration of both the top and subsoil keeping the underground soil temperature low and the moisture content high. It may therefore benefit burrowing amphibians like the purple frog to live in close proximity to termite colonies, which improve the quality of their habitat as well as providing a food source. In India, the purple frog from the southern Western Ghats may be the only known amphibian species that is a fully underground forager. All other burrowing frogs are either open burrow feeders or diurnal burrow dwellers that are open ground feeders in the night. Purple frogs require damp, loose soil to borrow into, and may dig themselves fully into appropriate soil within 3 to 5 minutes. When placed on hard ground, pebbled- or gravel-strewn soil, or areas with a thick mat of weeds, purple frogs are unable to borrow effectively and go in search of cover. The hind limbs have strong feet with wart-like structures that are primarily used for digging. This frog burrows downwards using its hind limbs like spades, throwing the soil over its back. They rest underground in a horizontal position with the limbs tucked under the body, although they do not remain idle underneath the soil, especially when foraging for their prey.
Habitat
The first purple frog was officially discovered in disturbed secondary forest near a cardamom plantation. It has also been found in disturbed secondary forest contiguous with montane evergreen forest. It presumably occurs in undisturbed forest as well and apparently does not survive in open, completely clear habitats. This species requires fairly loose, damp, well-aerated soil, especially in close proximity to termite colonies.
Distribution
This species is endemic to the Western Ghats in India, and is known from only two localities in the Idukki District in the Cardomom Hills, Kerala at an altitudinal range of 850 - 1,000m above sea level. These two areas are Kattapana and near Idukki town. It might occur more widely, but it seems that other reported localities probably refer to currently undescribed species.
Population Estimate
The purple frog is thought to be a rare species, although it is very hard to find which makes any population estimate difficult to determine. Only 135 individuals have so far been observed, and of these only three have been females. The plantation workers within the range of this species have reported that this frog is uncommonly found when they are cutting trenches during the monsoon period (June to October).
Population Trend
The purple frog is thought to be in decline by the IUCN Red List of Threatened Species.
Status
The purple frog is listed as Endangered in the IUCN Red List of Threatened Species because its extent of occurrence is less than 5,000 km sq., all individuals found are in fewer than five locations, and there is a continuing decline in the extent and quality of its habitat in the Cardomom Hills, Western Ghats.
Threats
The main threat to the purple frog is believed to be ongoing forest loss for coffee, cardamom, ginger and other species for cultivation.
Conservation Underway
It has not yet been found in any protected areas, although its range is an integral part of the peripheral hilly area that adjoins the Silent Valley National Park. There are no specific conservation measures ongoing for this species.
This species is endemic to the Western Ghats in India, and is known from only two localities in the Idukki District in the Cardomom Hills, Kerala at an altitudinal range of 850 - 1,000m above sea level. These two areas are Kattapana and near Idukki town. It might occur more widely, but it seems that other reported localities probably refer to currently undescribed species.
Population Estimate
The purple frog is thought to be a rare species, although it is very hard to find which makes any population estimate difficult to determine. Only 135 individuals have so far been observed, and of these only three have been females. The plantation workers within the range of this species have reported that this frog is uncommonly found when they are cutting trenches during the monsoon period (June to October).
Population Trend
The purple frog is thought to be in decline by the IUCN Red List of Threatened Species.
Status
The purple frog is listed as Endangered in the IUCN Red List of Threatened Species because its extent of occurrence is less than 5,000 km sq., all individuals found are in fewer than five locations, and there is a continuing decline in the extent and quality of its habitat in the Cardomom Hills, Western Ghats.
Threats
The main threat to the purple frog is believed to be ongoing forest loss for coffee, cardamom, ginger and other species for cultivation.
Conservation Underway
It has not yet been found in any protected areas, although its range is an integral part of the peripheral hilly area that adjoins the Silent Valley National Park. There are no specific conservation measures ongoing for this species.
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