Duttaphrynus Melanostictus Matheran Head

''Duttaphrynus melanostictus'' is commonly called Asian common toad, Asian black-spined toad, Asian toad, black-spectacled toad, common Sunda toad, and Javanese toad. It is probably a complex of more than one

true toad A true toad is any member of the family Bufonidae, in the order Anura (frogs and toads). This is the only family of anurans in which all members are known as toads, although some may be called frogs (such as harlequin frogs). The bufonids now ...

species that is widely distributed in

South South is one of the cardinal directions or compass points. The direction is the opposite of north and is perpendicular to both west and east. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Proto-Germanic ''*sunþa ...

and

Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...

. The species grows to about long. Asian common toads breed during the monsoon, and their tadpoles are black. Young toads may be seen in large numbers after monsoon rains finish.

Characteristics

The top of the head has several bony ridges, along the edge of the snout (canthal ridge), in front of the eye (preorbital), above the eye (supraorbital), behind the eye (postorbital), and a short one between the eye and ear (orbitotympanic). The snout is short and blunt, and the space between the eyes is broader than the upper eyelid width. The ear drum or tympanum is very distinct and is at least as wide as two-thirds the diameter of the eye. The first finger is often longer than the second and the toes are at least half webbed. A warty tubercle is found just before the junction of the thigh and shank (subarticular tubercle) and two moderate ones are on the shank (metatarsus). No skin fold occurs along the tarsus. The "knee" (tarsometatarsal articulation) reaches the tympanum or the eye when the hind leg is held parallel along the side of the body. The dorsal side is covered with spiny warts. The parotoids are prominent, kidney-shaped, or elliptical and elongated, and secrete milky white Bufotoxin. The dorsal side is yellowish or brownish and the spines and ridges are black. The underside is unmarked or spotted. Males have a subgular vocal sac and black pads on the inner fingers that help in holding the female during copulation.

Ecology and behaviour

Asian common toads breed in still and slow-flowing rivers and temporary and permanent ponds and pools. Adults are terrestrial and may be found under ground cover such as rocks,

leaf litter Plant litter (also leaf litter, tree litter, soil litter, litterfall, or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that has fallen to the ground. This detritus or dead organic material and its constituen ...

, and logs, and are also associated with human habitations. The

larvae A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect developmental biology, development such as insects, some arachnids, amphibians, or cnidarians typical ...

are found in still and slow-moving waterbodies. They are often seen at night under street lamps, especially when winged

termite Termites are a group of detritivore, detritophagous Eusociality, eusocial cockroaches which consume a variety of Detritus, decaying plant material, generally in the form of wood, Plant litter, leaf litter, and Humus, soil humus. They are dist ...

s swarm. They have been noted to feed on a wide range of

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

s, including

scorpion Scorpions are predatory arachnids of the Order (biology), order Scorpiones. They have eight legs and are easily recognized by a pair of Chela (organ), grasping pincers and a narrow, segmented tail, often carried in a characteristic forward cur ...

s. Tadpoles grown in sibling groups

metamorphosed Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...

faster than those that were kept in mixed groups. Tadpoles have been shown to be able to recognize kin. The 96h

LC50 In toxicology, the median lethal dose, LD50 (abbreviation for "lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a given substance. The value of LD50 for a substance is the dose requir ...

of commercial grade

malathion Malathion is an organophosphate insecticide which acts as an acetylcholinesterase inhibitor. In the USSR, it was known as carbophos, in New Zealand and Australia as maldison and in South Africa as mercaptothion. The compound's name is presumably ...

for the tadpoles is 7.5 mg/L and sublethal levels of exposure can impair swimming. Duttaphrynus melanostictus

Distribution and habitat

Asian common toads occur widely from northern

Pakistan Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...

through

Nepal Nepal, officially the Federal Democratic Republic of Nepal, is a landlocked country in South Asia. It is mainly situated in the Himalayas, but also includes parts of the Indo-Gangetic Plain. It borders the Tibet Autonomous Region of China Ch ...

Bangladesh Bangladesh, officially the People's Republic of Bangladesh, is a country in South Asia. It is the List of countries and dependencies by population, eighth-most populous country in the world and among the List of countries and dependencies by ...

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

including the

Andaman Andaman may refer to: * Andaman Islands, an island group in the Bay of Bengal * Andaman Island, Penang, an artificial island in George Town, Penang * Andaman Sea, a sea of the eastern Indian Ocean * ''Andaman'' (1998 film), an Indian Kannada-lang ...

and

Nicobar Islands The Nicobar Islands are an archipelago, archipelagic island chain in the eastern Indian Ocean. They are located in Southeast Asia, northwest of Aceh on Sumatra, and separated from Thailand to the east by the Andaman Sea. Located southeast of t ...

Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...

Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...

Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...

Laos Laos, officially the Lao People's Democratic Republic (LPDR), is the only landlocked country in Southeast Asia. It is bordered by Myanmar and China to the northwest, Vietnam to the east, Cambodia to the southeast, and Thailand to the west and ...

Vietnam Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...

Cambodia Cambodia, officially the Kingdom of Cambodia, is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. It is bordered by Thailand to the northwest, Laos to the north, and Vietnam to the east, and has a coastline ...

, southern

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...

Hong Kong Hong Kong)., Legally Hong Kong, China in international treaties and organizations. is a special administrative region of China. With 7.5 million residents in a territory, Hong Kong is the fourth most densely populated region in the wor ...

and

Macau Macau or Macao is a special administrative regions of China, special administrative region of the People's Republic of China (PRC). With a population of about people and a land area of , it is the most List of countries and dependencies by p ...

Malaysia Malaysia is a country in Southeast Asia. Featuring the Tanjung Piai, southernmost point of continental Eurasia, it is a federation, federal constitutional monarchy consisting of States and federal territories of Malaysia, 13 states and thre ...

Singapore Singapore, officially the Republic of Singapore, is an island country and city-state in Southeast Asia. The country's territory comprises one main island, 63 satellite islands and islets, and one outlying islet. It is about one degree ...

, and the

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

n islands of

Sumatra Sumatra () is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the list of islands by area, sixth-largest island in the world at 482,286.55 km2 (182,812 mi. ...

Java Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...

Borneo Borneo () is the List of islands by area, third-largest island in the world, with an area of , and population of 23,053,723 (2020 national censuses). Situated at the geographic centre of Maritime Southeast Asia, it is one of the Greater Sunda ...

Anambas Anambas Islands Regency () is an island regency in the Riau Islands Province, Indonesia, located in the Natuna Sea. The regency consists of 255 islands, including five outer islands that are important for Indonesia's sovereignty boundaries, n ...

and

Natuna Islands Natuna Regency is an islands regency located in the northernmost part of the Province of Riau Islands, Indonesia. It contains at least 154 islands, of which 127 of them are reported as uninhabited. This archipelago, with a land area of 1,978.4 ...

. They have been recorded from sea level up to altitude, and live mostly in disturbed lowland habitats, from upper beaches and riverbanks to human-dominated agricultural and urban areas. They are uncommon in closed forests.

Introductions

Madagascar

''D. melanostictus'' arrived in

Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...

in 2011 at the port of

Toamasina Toamasina (), meaning "like salt" or "salty", unofficially and in French language, French Tamatave or in the past as Port aux prunes, is the capital of the Atsinanana region on the east coast of Madagascar on the Indian Ocean. The city is the chief ...

, and by 2014, was found in a zone around that city. Since its discovery on the east coast, a grave fear has developed that if the Asian toad is not eradicated from Madagascar and stronger quarantines are not developed to prevent reinvasion, it could have comparable impacts to those of

cane toads in Australia The cane toad in Australia is regarded as an exemplary case of an invasive species. Australia's relative isolation prior to History of Australia (1788–1850), European colonisation and the Industrial Revolution, both of which dramatically in ...

. Because – like Australia's – Madagascar's native predators have been isolated from bufonids since the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

, they are thought to lack resistance to toad toxins as found in natural

varanid The Varanidae are a family of lizards in the superfamily Varanoidea and order Anguimorpha. The family, a group of carnivorous and frugivorous lizards, includes the living genus '' Varanus'' and a number of extinct genera more closely related ...

and snake predators of ''D. melanostictus'' in its native range. One study analyzed the sequences of the Na+/K+-ATPase gene (sodium-potassium pump) in dozens of Malagasy species that may be feeding on ''D. melanostictus.'' It was found that all but one out of 77 species failed to show evidence of resistance to the toad toxin, which strongly suggests that these alien toads can significantly impact the native Malagasy animal life and contribute to the worsening

biodiversity crisis Biodiversity loss happens when plant or animal species disappear completely from Earth (extinction) or when there is a decrease or disappearance of species in a specific area. Biodiversity loss means that there is a reduction in biological dive ...

in the region. Nevertheless, evidence from one Australian species, the bluetongue lizard, ''Tiliqua scincoides'', produces the possibility that some Malagasy animals do possess resistance to bufotenin because almost identical cardiac glycosides are produced by native plants of the genus ''

Bryophyllum ''Bryophyllum'' (from the Greek ''bryon/bryein'' = sprout, ''phyllon'' = leaf) is a group of plant species of the family (biology), family Crassulaceae native to Madagascar. It is a Section (botany), section or subgenus within the genus ''Kalan ...

''.

Wallacea and West Papua

''D. melanostictus'' was introduced to the Indonesian island of

Bali Bali (English:; Balinese language, Balinese: ) is a Provinces of Indonesia, province of Indonesia and the westernmost of the Lesser Sunda Islands. East of Java and west of Lombok, the province includes the island of Bali and a few smaller o ...

in 1958,Reilly, Sean B.; Wogan, Guinevere O. U.; Stubbs, Alexander L.; Arida, Evy; Iskandar, Djoko T. and McGuire Jimmy A.; ‘ Toxic toad invasion of Wallacea: A biodiversity hotspot characterized by extraordinary endemism’; ''Global Change Biology''; August 2017, pp. 1-3

Sulawesi Sulawesi ( ), also known as Celebes ( ), is an island in Indonesia. One of the four Greater Sunda Islands, and the List of islands by area, world's 11th-largest island, it is situated east of Borneo, west of the Maluku Islands, and south of Min ...

in 1974, then subsequently to Ambon,

Lombok Lombok, is an island in West Nusa Tenggara province, Indonesia. It forms part of the chain of the Lesser Sunda Islands, with the Lombok Strait separating it from Bali to the west and the Alas Strait between it and Sumbawa to the east. It is rou ...

Sumba Sumba (; ), natively also spelt as Humba, Hubba, Suba, or Zuba (in Sumba languages) is an Indonesian island (part of the Lesser Sunda Archipelago group) located in the Eastern Indonesia and administratively part of the East Nusa Tenggara pro ...

Sumbawa Sumbawa, is an Indonesian island, located in the middle of the Lesser Sunda Islands chain, with Lombok to the west, Flores to the east, and Sumba further to the southeast. Along with Lombok, it forms the province of West Nusa Tenggara, but th ...

Timor Timor (, , ) is an island at the southern end of Maritime Southeast Asia, in the north of the Timor Sea. The island is Indonesia–Timor-Leste border, divided between the sovereign states of Timor-Leste in the eastern part and Indonesia in the ...

and

Indonesian New Guinea Western New Guinea, also known as Papua, Indonesian New Guinea, and Indonesian Papua, is the western half of the island of New Guinea, formerly Dutch and granted to Indonesia in 1962. Given the island is alternatively named Papua, the region ...

Manokwari Manokwari is a coastal town and the capital city, capital of the Provinces of Indonesia, Indonesian province of West Papua (province), West Papua. It is one of only seven provincial capitals of Indonesia without a city status in Indonesia, city ...

on the

Vogelkop Peninsula The Bird's Head Peninsula (Indonesian: , , meaning Bird's Head in Indonesian and Dutch) or Doberai Peninsula (''Semenanjung Doberai'') is a large peninsula that makes up the northwest portion of the island of New Guinea, comprising the Indonesia ...

. The species is now common at Sentani in far eastern

Papua Province Papua is a province of Indonesia, comprising the northern coast of Western New Guinea together with island groups in Cenderawasih Bay to the west. It roughly follows the borders of the Papuan customary region of Tabi Saireri, and is divided in ...

. The absence of resistance to toad toxins in native snake and varanid predators means that these species could suffer severe declines from the inadvertent spread of the Asian common toad via human traffic, and the currently

near threatened A near-threatened species is a species which has been Conservation status, categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature (IUCN) as that may be vulnerable to Endangered species, endangerment in the ne ...

New Guinea quoll is also almost certain to be further affected in the lower-altitude portion of its range.Covacevich, Jeanette, and Archer, Mike; ‘The distribution of the cane toad, ''Bufo marinus'' in Australia and its effects on indigenous vertebrates’; ''Memoirs of the Queensland Museum'', volume 17 (1975), pp. 305–310.

An unwanted species in Australia

The Asian common toad has been detected in Australia at least four times since 2000. The Asian common toad has been described as one of Australia's "10 most unwanted" species, and "potentially more damaging than the cane toad". It may cause serious ecological problems due to "competition with native species, its potential to spread exotic parasites and pathogens and its toxicity".Invasive Species Council, 2014, Biosecurity Failures in Australia, The Asian Black-Spined Toad, https://invasives.org.au/wp-content/uploads/2014/09/Biosecurity-failures-asian-black-spined-toads.pdf; retrieved 2017-05-28 Like cane toads, the Asian common toad secretes toxins from glands in their backs to deter predators. These toxins would beyond reasonable doubt severely affect native predators, such as

snake Snakes are elongated limbless reptiles of the suborder Serpentes (). Cladistically squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales much like other members of the group. Many species of snakes have s ...

goanna A goanna is any one of several species of lizard of the genus ''Monitor lizard, Varanus'' found in Australia and Southeast Asia. Around 70 species of ''Varanus'' are known, 25 of which are found in Australia. This varied group of carnivorous r ...

s and

quoll Quolls (; genus ''Dasyurus'') are carnivorous marsupials native to Australia and New Guinea. They are primarily nocturnal, and spend most of the day in a den. Of the six species of quoll, four are found in Australia and two in New Guinea. Anot ...

s. The recent rate of incursions suggests a high likelihood of establishment in Australia. So, experts are calling for the Australian government to develop a "high-priority contingency plan" that includes stronger environmental quarantine and surveillance strategies.Massam M, Kirkpatrick W and Page A (2010). ''Assessment and Prioritisation of Risk for Forty Introduced Animal Species''. Invasive Animals Cooperative Research Centre, Canberra