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Duttaphrynus melanostictus

By Justin Gelb

Geographic Range

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. ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Khan, 2000; Lever, 2003)

Habitat

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) ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Khan, 2000)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • temporary pools
  • Range elevation
    0 to 2000 m
    0.00 to 6561.68 ft

Physical Description

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). ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Khan, 2000; Mercy, 1999; van Dijk, et al., 2011)

  • Sexual Dimorphism
  • male larger
  • Range length
    57 to 83 mm
    2.24 to 3.27 in

Development

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). ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Mogali, et al., 2011; Saidapur and Girish, 2001)

Reproduction

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). ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Khan, 2000; Mercy, 1999; Saidapur and Girish, 2001)

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). ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Khan, 2000; Mercy, 1999; 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

There is no parental care in Asian common toads (Kahn 2000, Mercy 1999, The State of Queensland 2010, Saidapur and Girish 2001) ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Khan, 2000; Mercy, 1999; Saidapur and Girish, 2001)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

Asian common toads live an average of 4 years in the wild and up to 10 years in captivity. ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Khan, 2000; Mercy, 1999; Saidapur and Girish, 2001)

  • Average lifespan
    Status: wild
    4 years
  • Range lifespan
    Status: captivity
    10 (high) years

Behavior

Asian common toads are nocturnal; during the day adults will hide under rocks, leaf litter, logs, and human made structures (drains, garbage piles, and houses). The toads are slow moving and fairly timid. Asian common toads are insectivorous and are known to feed on many insect pests known to humans (Kahn 2000, Mogali et al 2011, The State of Queensland 2010). ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Khan, 2000; Mogali, et al., 2011)

Home Range

Asian common toads are not known to have specified territory size; home range is dictated by the availability of potential food items in a given area. ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Khan, 2000; Mogali, et al., 2011)

Communication and Perception

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). ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Mercy, 1999)

Food Habits

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). ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Mercy, 1999)

  • Animal Foods
  • amphibians
  • eggs
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • terrestrial worms

Predation

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). ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Keomany, et al., 2007; Mercy, 1999)

Ecosystem Roles

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). ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Keomany, et al., 2007; Khan, 2000; Mercy, 1999; van Dijk, et al., 2011)

Economic Importance for Humans: Positive

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. (Mercy, 1999)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

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). (Church, 1960; Lever, 2003)

Conservation Status

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). ("Pest Risk Assessment: Asian spined toad (Bufo melanostictus)", 2010; Church, 1960; Harper, et al., 2009; Lever, 2003; Mercy, 1999; Sumandasa, et al., 2007)

Contributors

Justin Gelb (author), Michigan Technological University, Amy Schrank (editor), Michigan Technological University, Laura Podzikowski (editor), Special Projects.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

insectivore

An animal that eats mainly insects or spiders.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

poisonous

an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

suburban

living in residential areas on the outskirts of large cities or towns.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

References

The State of Queensland, Department of Employment, Economic Development and Innovation. Pest Risk Assessment: Asian spined toad (Bufo melanostictus). PR10_5469. Queensland, Australia: The State of Queensland. 2010. Accessed March 02, 2012 at http://www.daff.qld.gov.au/documents/Biosecurity_EnvironmentalPests/IPA-Asian-Toad-Risk-Assessment.pdf.

Berry, P., J. Bullock. 1962. The Food of the Common Malayan Toad, Bufo melanostictus Schneider. Copeia, 1962/4: 736-741.

Church, G. 1960. The Invasion of Bali by Bufo melanostictus. Herpetologica, 16/1: 15-21.

Harper, B., B. Luukinen, J. Gervais, K. Buhl, D. Stone. 2009. "Diazinon Technical Fact Sheet" (On-line pdf). National Pesticide Information Center, Oregon State University Extension Services. Accessed April 11, 2012 at http://npic.orst.edu/factsheets/diazinontech.pdf.

Keomany, S., M. Mayxay, P. Souvannasing, C. Vilayhong, B. Stuart, L. Srour, P. Newton. 2007. Toad Poisoning in Laos. The American Society of Tropical Medicine and Hygiene, 77/5: 850–853.

Khan, M. 2000. "Duttaphrynus melanostictus" (On-line). AmphibiaWeb. Accessed February 17, 2012 at http://amphibiaweb.org/cgi-bin/.

Lever, C. 2003. Naturalized Reptiles and Amphibians of the World. New York: Oxford University Press.

Mercy, M. 1999. "Studies on some aspects of the Biology and Ecology of the Common Indian Toad Bufo melanostictus Schneider (Class Amphibia; Order Anura)" (On-line). Mahatma Gandhi University Online Theses Library.

Mogali, S., S. Saidapur, B. Shanbhag. 2011. Levels of Predation Modulate Antipredator Defense Behavior and Metamorphic Traits in the Toad Bufo melanostictus. Journal of Herpetology, 45/4: 428-431.

Saidapur, S., S. Girish. 2001. Growth and Metamorphosis of Bufo melanostictus Tadpoles: Effects of Kinship and Density. Journal of Herpetology, 35/2: 249- 254.

Sumandasa, D., M. Wijesinghe, W. Ratnasooriya. 2007. Effects of diazinon on larvae of the Asian Common Toad (Duttaphrynus melanostictus Schneider 1799). Environmental Toxicology, 27.11: 2320-2325.

van Dijk, P., D. Iskandar, M. Lau, G. Huiqing, G. Baorong, L. Kuangyang, C. Wenhao, Y. Zhigang, B. Chan, S. Dutta, R. Inger, K. Manamendra-Arachchi, M. Khan. 2011. "Duttaphrynus melanostictus" (On-line). ICUN Red List. Accessed March 02, 2012 at http://www.iucnredlist.org/apps/redlist/details/54707/0.

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