Asian common toads live an average of 4 years in the wild and up to 10 years in captivity.
Average lifespan
Status: wild: 4 years.
Range lifespan
Status: captivity: 10 (high) years.
Predation on Asian common toads are variable because of their extremely large range; throughout their range snakes and birds are common predators. These toads are toxic and can cause illness and death in humans. This could be a possible reason why Asian common toads do not have many predators (Keomany 2007, Mercy 1999, The State of Queensland, 2010).
Asian common toads are stout, mid to large sized toads with a modestly sized head and short limbs. They have thick dry skin with prominent cranial ridges and protruding parotid gland. The tympana are oval or circular in shape, stand out well and are about 2/3rds the size of the eyes (Mercy 1999). Snout-vent length of males ranges from 57 to 83 mm and females range between 65 and 85 mm. Elevated ridges appear on head, and eyelids have a long dark crest around the boarder. Colors are extremely variable throughout this species and can range from plain brick red to almost fully black. The most common color pattern is pale yellow-brown marked boldly with dark or reddish brown streaks and spots. Their backs are covered with a series of warts varying in sizes; warts are encircled with black or dark pigments and have spines protruding. Males have a subgular vocal sac; breeding males have a throat region that is bright yellow orange and the inner side of the first and second fingers have nuptial pads. Juveniles possess a black band around the throat that runs between the chin and the breast. Juveniles do not have warts and have a very small Tympanum. Tadpoles are back, small around 15 mm in size and are found in groups (Khan 2000, Mercy 1999, The State of Queensland 2010, van Dijk et al 2011).
Range length: 57 to 83 mm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; poisonous
Sexual Dimorphism: male larger
Asian common toads are nocturnal terrestrial toads that are found throughout, subtropical, and tropical habitats up to 2000 meters above sea level. Asian common toads are generalists when it comes to choosing a habitat, but they prefer lowland areas such as lowland disturbed forests, forest margins, riparian areas, dense evergreen forests, gardens, and human dominated agricultural and urban areas. (Khan 2000, Mercy 1999, The State of Queensland 2010)
Range elevation: 0 to 2000 m.
Habitat Regions: temperate ; tropical ; terrestrial ; freshwater
Terrestrial Biomes: forest ; rainforest
Aquatic Biomes: lakes and ponds; rivers and streams; temporary pools
Wetlands: marsh ; swamp ; bog
Other Habitat Features: urban ; suburban ; agricultural ; riparian
Asian common toads (Duttaphrynus melanostictus) have a wide distribution across Asia. The native distribution extends north from Pakistan through Nepal, Bangladesh, India, Sri Lanka, Southern China, Myanmar, Lao, Vietnam, Thailand, Cambodia, Malaysia, Singapore, and Indonesia (Sumatra, Java, Borneo and Natuna Islands).
Asian common toads have been naturalized in Indonesia (Bali, Sulawi, Ambon, Manokwari and Maluku), New Guinea (West Papua and New Guinea), and the Andaman Nicobar Islands. B. melanostictus has also been recently found in East Timor.
Biogeographic Regions: oriental (Native ); australian (Introduced , Native ); oceanic islands (Introduced , Native )
Asian common toads are insectivorous although these toads are also know to be an opportunist and will feed on a variety of arthropods and even mollusks. An analysis of the stomach contents of multiple specimens of Asian common toads yielded arthropod orders such as earwigs, grasshoppers, crickets, weta, and locusts, true bugs, moths and butterflies, beetles, typical bugs, sawflies, wasps, bees and ants, termites, cockroaches, and mantids, true flies, centipedes, and millipedes. Though these toads are opportunistic feeders the insects that showed the greatest abundance in the stomach were sawflies, wasps, bees and ants, beetles and termites. This toad is feeds on insects that are known pests to human such mosquitoes and various crop pests (Mercy 1999, The State of Queensland 2010).
Animal Foods: amphibians; eggs; insects; terrestrial non-insect arthropods; mollusks; terrestrial worms
Primary Diet: carnivore (Insectivore , Eats non-insect arthropods, Vermivore)
Asian common toads are an important insectivore, because they feeds on many insect pests known to humans. These toads have few natural predators; although they have been known to be preyed upon by snakes and birds. The possible introduction of these toads could be detrimental to a new ecosystem. Consuming anurans as a food source in Southeast and Southern Asia is a common practice; Asian common toads are fairly toxic and they have caused many deaths and illnesses in Lao and Taiwan (Keomany 2007, Khan 2000, Mercy 1999, The State of Queensland 2010, van Dijk et al 2011).
Asian common toads have a wide diet throughout their range. In Mercy (1999) found evidence that these toads eat insects that are known to be a problem to farmers in India.
Positive Impacts: controls pest population
Asian common toads have been introduced to the islands of Bali, Papua New Guinea, Sulawesi, Andaman and Nicobar. The ways in which these toads have been introduced is not fully known in most areas, although in some areas it is assumed that Asian common toads first occurred on these islands when they were fist settled. In other cases, such as in Papua New Guinea, it is rumored that the Department of Health released these toads as means to control mosquito populations These toads are understood to be reproducing rapidly in these areas; there is a possibility that Asian common toads are displacing a smaller species of toads such as crested toads. Asian common toads are suspected to cause intense ecological damage. On the islands where Asian common toads have become naturalized it is competing heavily for similar resources of native anurans. These toads are also known to feed on the eggs, larva and juveniles of other native amphibians, which further exasperates the added competition. This competition may in the future resemble the ecological crisis of cane toads in Australia (Church 1960, Lever 2003, The State of Queensland 2010).
Negative Impacts: injures humans (poisonous )
Asian common toads have typical anuran development which is indirect with an aquatic tadpole stage. Eggs become larva within 24 and 28 hours. Saidapur and Girish (2001) showed that Asian common toad tadpoles reared with sibling groups grow at a higher rate and develop faster compared to larvae reared in mixed groups. Because females produce so many eggs, intraspecific competition among tadpoles is likely intense in the ephemeral pools in which this species breeds. Therefore, Saidapur and Girish (2001) suggested that the rapid growth and development of tadpoles in the presence of siblings helps increase reproductive success. A study done by Mogali et al (2011) illustrates that tadpoles of Asian common toads will emerge at different times and sizes with the presents of predators. When predators are present tadpoles will decrease in body mass up to 46% and metamorphosis will also occur earlier (Mogali et al 2011,The State of Queensland 2010, Saidapur and Girish 2001).
Development - Life Cycle: metamorphosis ; indeterminate growth
Asian common toads are listed on the International Union for Conservation of Nature (IUCN) Red list as “Least Concern”. In the regions of the world that these toads have become naturalized, populations are on the rise. These toads are becoming increasingly common, although pesticide run off can become a detriment to them if it is not monitored. Sumanadasa et al’s (2007) study showed that exposure to small levels of an insecticide called diaznon resulted in almost 100% death of Asian common toads. This chemical is highly regulated by the United States and European Union, yet it is still used widely throughout the developing counties of Asia (Church 1960, Harper et al 2009, Lever 2003, Mercy 1999, Sumanadasa et al 2007, The State of Queensland 2010).
Male Asian common toads will call during the breeding season to attract females; the call that is used is can be described as melodic “creo-o,o; cro-ro-ro-ro-ro-ro-ro” or “curr, curr, curr”. Beyond calling during mating Asian common toads are not known to make any other vocalizations (Mercy 1999, The State of Queensland 2010).
Communication Channels: acoustic
Other Communication Modes: vibrations
Perception Channels: visual ; tactile ; acoustic ; vibrations
Breeding is water dependent. In areas with a clear wet and dry season breeding will typically happen at the beginning of the wet season. In areas with no lack of moisture breeding will persist year round. The lunar cycle dictates ovulation, which occurs just before or after a full moon. The ovaries can make up 30% of the total body weight at this time. The female will lay a long string of black eggs, which are externally fertilized by the male. Eggs are enclosed in a thick mucus membrane and deposited on submerged vegetation. Eggs are usually laid in a temporary pond or vernal pool. Huang et al (1997) suggested male Asian common toads have a continuous spermatogenic cycle; in other words, sperm cells are produced year round. Thus, mating for males is not seasonally dependent in areas that are continuously moist. Although in more temperate regions with a clear wet and dry season, Asian common toads have been shown to favor specific seasons, a study done in Taiwan showed that there was a larger concentration of spermatophores in the male toad during a specific time of the year (Kahn 2000, Mercy 1999, The State of Queensland 2010, Saidapur and Girish 2001).
Mating System: polygynandrous (promiscuous)
Asian common toads breed opportunistically in small lentic bodies of natural and man-made fresh water. Males congregate at breeding sites and call females. The call can be noted as sounding like “creo-o,o; cro-ro-ro-ro-ro-ro-ro”. There intense competition amongst males for females; many males are often found clinging to a single female (Kahn 2000, Mercy 1999, The State of Queensland 2010, Saidapur and Girish 2001).
Breeding interval: Asian common toads breed twice per year.
Breeding season: Asian common toads breed during the wet season in seasonal areas.
Average number of offspring: 40,000 eggs per clutch .
Range time to hatching: 24 to 48 hours.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous
There is no parental care in Asian common toads (Kahn 2000, Mercy 1999, The State of Queensland 2010, Saidapur and Girish 2001)
Parental Investment: no parental involvement
Duttaphrynus melanostictus, known as the Asian common toad, is widely distributed in South and Southeast Asia. It goes by a multitude of other common names including Asian toad, black-spectacled toad, black spined toad, common Sunda toad and Javanese toad.Ecological, geographical and genetic analyses have distinguished three distinct lineages (Asian mainland, coastal Myanmar, and Sundaic islands).It is probable that D. melanostictus is actually a complex of multiple species, but more research is needed to confirm species delineations (Wogan et al. 2016).
Asian common toads live in a wide variety of tropical Southeast Asian habitats, especially disturbed lowland areas.They are recorded from sea level up to 1,800 m (5,900ft) in altitude and are considered a “human commensal” as they thrive in human-dominated agricultural and urban areas. Scientists estimate the original range of this species around the Myanmar-China border.These toads easily disperse as a result of human activities, leading Wogan et al. (2016) to describe them as tropical Asia’s “weediest” amphibian. Common Asian toads have invaded Borneo, Sulawesi, Seram, Indonesian New Guinea and multiple other Indonesian islands.Most recently this species was brought to Madagascar where it has spread rapidly.Its presence poses dire threats to native amphibians and other fauna as a predator, competitor, toxic threat to potential mammalian, avian and reptilian predators, and disease bearer (Kolby 2014).Wogan et al. compare its potential impact in Asia (and beyond) to that of the Cane toad (Rhinella marina) across Australia and Oceania.
Asian toads are a large species; females can grow to 20cm (8in) snout-vent length. Males are considerably smaller in size. Their dorsum can be yellow, red, brown or grey and is covered with black spiny warts and ridges.These wart patterns are unique and used in studies to identify individuals. Their underside is off-white in color, unmarked or spotted. They have a distinct tympanum (ear drum). Males have a subgular vocal sac and black pads on the inner fingers that help in holding the female during copulation (Khan and Koo 2016; van Dijk et al. 2004)
Adult toads are terrestrial and nocturnal.During the day they return to a selected hiding place with several other individuals.These daytime hiding spots may be holes or crevices or cover of rocks, leaf-litter and logs. Adults are active at night and feed upon a wide variety of invertebrates. They are slow and shy. In urban areas they frequently hunt insects attracted to streetlights, especially in times when winged termites swarm (Khan and Koo 2016; van Dijk et al. 2004).
The monsoon season often triggers breeding, although in some areas these toads breed year round.Males congregate around slow moving rivers, ponds, and pools calling with a “curr, curr, curr” to attract females.(Call recordings are available at http://amphibiaweb.org/cgi/amphib_query?where-genus=Duttaphrynus&where-species=melanostictus&account=amphibiaweb).Far outnumbered by males, females are quickly pounced upon by aggressive suitors and held in a nuptial clasp.Females lay a double jelly string containing the eggs, which gets entangled in vegetation in the waterbodies.The uniformly black tadpoles school in large groups, eating algae. Studies show that the tadpoles can recognize their kin.They grow to 26-27 mm in length before they metamorphose, then leave the water in swarms of froglets, many of which succumb to predators (Khan and Koo 2016; van Dijk et al. 2004).
Although the Asian toad is common, widespread and listed as “of least concern” by the IUCN, further research into the hidden diversity of D. melanostictus (in the form of distinct lineages and cryptic species included in this species name) may have some conservation implications as this becomes better understood (Wogan et al. 2016; Rowley et al. 2010).Asian toads are sometimes found in the pet trade, and eaten in northern Thailand (Khan and Koo 2016; van Dijk et al. 2004).
Kolby J.E. 2014 Ecology: stop Madagascar's toad invasion now. Nature 509, 563. (doi:10.1038/509563a)
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 species that is widely distributed in South and Southeast Asia.[1]
The species grows to about 20 cm (8 in) 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.
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.[2]
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, and logs, and are also associated with human habitations. The larvae are found in still and slow-moving waterbodies.[1] They are often seen at night under street lamps, especially when winged termites swarm. They have been noted to feed on a wide range of invertebrates, including scorpions.[3] Tadpoles grown in sibling groups metamorphosed faster than those that were kept in mixed groups.[4] Tadpoles have been shown to be able to recognize kin.[5] The 96h LC50 of commercial grade malathion for the tadpoles is 7.5 mg/L and sublethal levels of exposure can impair swimming.[6]
Asian common toads occur widely from northern Pakistan through Nepal, Bangladesh, India including the Andaman and Nicobar Islands, Sri Lanka, Myanmar, Thailand, Laos, Vietnam, Cambodia, southern China, Taiwan, Hong Kong and Macau to Malaysia, Singapore, and the Indonesian islands of Sumatra, Java, Borneo, Anambas and Natuna Islands. They have been recorded from sea level up to 1,800 m (5,900 ft) 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.[1]
D. melanostictus arrived in Madagascar in 2011 at the port of Toamasina, and by 2014, was found in a 100 km2 (39 sq mi) zone around that city.[7]
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.[8] Because – like Australia's – Madagascar's native predators have been isolated from bufonids since the Jurassic, they are thought to lack resistance to toad toxins as found in natural varanid[9] and snake predators of D. melanostictus[10][11] 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 in the region.[12][13]
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.[14]
D. melanostictus was introduced to the Indonesian island of Bali in 1958,[15] Sulawesi in 1974, then subsequently to Ambon, Lombok, Sumba, Sumbawa, Timor and Indonesian New Guinea at Manokwari on the Vogelkop Peninsula. The species is now common at Sentani in far eastern Papua Province.[16][17] 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,[15] and the currently near threatened New Guinea quoll is also almost certain to be further affected in the lower-altitude portion of its range.[18]
The Asian common toad has been detected in Australia at least four times since 2000.[19][20] The most recent incursion, in 2015, was in suburban Sydney.[20]
The Asian common toad has been described as one of Australia's “10 most unwanted” species, and “potentially more damaging than the cane toad”.[21] It may cause serious ecological problems due to “competition with native species, its potential to spread exotic parasites and pathogens and its toxicity”.[22] 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 snakes, goannas[23] and quolls.[18]
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.[24][22]
From Matheran, India 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 species that is widely distributed in South and Southeast Asia.
The species grows to about 20 cm (8 in) 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.
