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.
- Biogeographic Regions
- oriental
- australian
- oceanic islands
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)
- Habitat Regions
- temperate
- tropical
- terrestrial
- freshwater
- Terrestrial Biomes
- forest
- rainforest
- Aquatic Biomes
- lakes and ponds
- rivers and streams
- temporary pools
- Other Habitat Features
- urban
- suburban
- agricultural
- riparian
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).
- Other Physical Features
- ectothermic
- heterothermic
- bilateral symmetry
- poisonous
- Sexual Dimorphism
- male larger
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).
- Development - Life Cycle
- metamorphosis
- indeterminate growth
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).
- 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).
- Key Reproductive Features
- iteroparous
- year-round breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- fertilization
- 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
Lifespan/Longevity
Asian common toads live an average of 4 years in the wild and up to 10 years in captivity.
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).
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.
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).
- Communication Channels
- acoustic
- Other Communication Modes
- vibrations
- Perception Channels
- visual
- tactile
- acoustic
- vibrations
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).
- Primary Diet
-
carnivore
- insectivore
- eats non-insect arthropods
- vermivore
- 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).
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).
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.
- 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).
- Negative Impacts
- injures humans
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).
Additional Links
Contributors
Justin Gelb (author), Michigan Technological University, Amy Schrank (editor), Michigan Technological University, Laura Podzikowski (editor), Special Projects.
- oriental
-
found in the oriental region of the world. In other words, India and southeast Asia.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Australian
-
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
- introduced
-
referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- 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.
- introduced
-
referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- 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).
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- terrestrial
-
Living on the ground.
- freshwater
-
mainly lives in water that is not salty.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- 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.
- marsh
-
marshes are wetland areas often dominated by grasses and reeds.
- swamp
-
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
- 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.
- urban
-
living in cities and large towns, landscapes dominated by human structures and activity.
- suburban
-
living in residential areas on the outskirts of large cities or towns.
- agricultural
-
living in landscapes dominated by human agriculture.
- riparian
-
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- ectothermic
-
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- 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.
- 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.
- 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).
- 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.
- indeterminate growth
-
Animals with indeterminate growth continue to grow throughout their lives.
- polygynandrous
-
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
- 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).
- year-round breeding
-
breeding takes place throughout the year
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- fertilization
-
union of egg and spermatozoan
- external fertilization
-
fertilization takes place outside the female's body
- oviparous
-
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- nocturnal
-
active during the night
- motile
-
having the capacity to move from one place to another.
- acoustic
-
uses sound to communicate
- vibrations
-
movements of a hard surface that are produced by animals as signals to others
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- vibrations
-
movements of a hard surface that are produced by animals as signals to others
- 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).
- carnivore
-
an animal that mainly eats meat
- insectivore
-
An animal that eats mainly insects or spiders.
References
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 ( Bufo 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 .
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 .