Bufo asper has a large and stout body. The females have a snout-vent length of 95-140 mm, while the males have a snout-vent length of 70-100 mm. The skin is covered with warts or tubercles; the name of this species derives from its rough skin texture. The head is broad and blunt, without bony crests. This toad has an ovoid parotoid gland connected to the supraorbital ridge by a supratympanic ridge. The tympanum is visible. The hands and feet are spinous. The fourth toe is the longest, and all the toes except the fourth are fully webbed. Males have nuptial pads on the base of the first finger. Bufo asper is usually dark brown, gray or black in color, with black spotting ventrally. Males have a blackish coloring on their throats
(Iskandar 1998; Inger and Stuebing 2005; Inger and Bacon 1968).
Bufo asper tadpoles are small, reaching 12-15 mm before metamorphosis. The body is oval and somewhat flattened. The tail is leaf-shaped, rounded with a narrow tip. The lower lip is quite wide
(Inger and Stuebing 2005), with the cuplike mouth enabling the tadpole to adhere to the bottom substrate in flowing water
(Iskandar 1998). The denticle formula is II/III. Tadpole coloration is either all black or dark brown
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Brunei Darussalam, Indonesia, Malaysia, Myanmar, Thailand, Viet Nam
Malaysian region distribution from AmphibiaWeb's database: Peninsular Malaysia, Sabah, Sarawak
This species can be found in primary and old secondary rainforests of Indonesia, Malaysia, Thailand, Myanmar and Borneo, up to 1500 m above sea level (Iskandar, 1998; Inger et al., 1974). It has also been reported to occur in Vietnam, at the border of Gia Lai and Dac Lac provinces to the northwest of Plei Tung Than; in Vietnam it occurs at about 700 m in elevation
(Nguyen et al. 2005). It is likely also to occur in intervening Cambodia and Laos, but has not yet been reported from these countries. Bufo asper lives along banks of small to medium-sized streams (3-30 m wide) and large rivers
(Inger at al. 1974).
Life History, Abundance, Activity, and Special Behaviors
Bufo asper is nocturnal and partially aquatic, coming out at night and hiding under submerged stones during the day (Iskandar, 1998). It lives along stream banks rather than wandering through the forest, almost always remaining within 2 m of the water's edge
(Inger et al. 1974). On Bornean streams, the median home ranges vary from 43-75 m
(Inger et al. 1974).
Males call to females from widely spaced sites along the stream banks at night, particularly when there is a full moon
(Inger 1969; Iskandar 1998).
The call has been described as a raspy chirp, which is sometimes repeated
(Inger and Stuebing 2005). They do not form choruses
(Emerson and Hess 1996). This species appears to reproduce year-round, as both sperm and eggs are produced throughout the year
(Inger and Bacon 1968). Ripe ova have a diameter of 1.26 mm
(Inger and Bacon 1968). This species lays huge clutches, with an average size of 12,792 eggs per clutch
(Inger and Bacon 1968). Bufo asper prefers to lay its eggs in quiet portions of streams, as
metamorphosing larvae were found at the edges of side pools of streams in Borneo
(Inger et al. 1974). The tadpoles are somewhat flattened, and typically adhere to the bottom of streams with slow to medium currents using their subterminal, cuplike mouths. The lips are enlarged, enabling bottom feeding
Bufo asper adults do not move much on a given day
(Inger and Stuebing 2005). However, these toads have been found to show net movement (distance between the point of first and last capture over a given time period) of up to 465 m over a period of 180 days
(Inger 2003). It has been hypothesized that this vagility may have allowed Bufo asper to disperse between the continent and Borneo over relatively short periods of sea regression during the Pleistocene
Trends and Threats
This species is quite resilient. Although B. asper is affected by habitat loss and pollution, it has managed to survive in areas where many other frog species have disappeared, particularly on Sumatra and Java
(Iskandar 1998; IUCN 2006). However, populations in Malaysian forest fragments were shown to have a relative lack of genetic diversity (vs. B. parvus and B. melanostictus), which reflects the coincidence of Bufo asper breeding and feeding areas, linear home ranges, and lack of breeding aggregations
(Inger et al. 1974).
Relation to Humans
This frog is consumed for food in Sabah and peninsular Malaysia
Possible reasons for amphibian decline
General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Skin toxins from Bufo asper were able to induce the following significant
effects on mice at a dose of 100 mg/mouse: locomotor difficulties, prostration,
and convulsions, with partial recovery after 5 hours. The major toxic component
in Bufo asper skin extracts is bufotalin (a bufadienolide), with a lesser
component of resibufogenin and minor amounts of other bufadienolides and
(Daly et al. 2004).
The diploid chromosome number is 22, with five pairs of large chromosomes and
six pairs of smaller chromosomes
Daly, J. W., Noimai, N., Kongkathip, B., Kongkathip, N., Wilham, J. M., Garraffo, H. M., Kaneko, T., Spande, T. F., Ninit, Y., Nabhitabhata, J., and Chan-Ard, T. (2004). ''Biologically active substances from amphibians: preliminary studies on anurans from twenty-one genera of Thailand.'' Toxicon, 44, 805-815.
Emerson, S. B., and Hess, D. L. (1996). ''The role of androgens in opportunistic breeding tropical frogs.'' General and Comparative Endocrinology, 103, 220-230.
IUCN, Conservation International, and NatureServe. (2006). Global Amphibian Assessment: Bufo asper. www.globalamphibians.org. Accessed on 23 November 2007.
Inger, R. F. (1969). ''Organization of communities of frogs along small rain forest streams in Sarawak.'' Journal of Animal Ecology, 38, 123-148.
Inger, R. F. (2003). ''Sampling biodiversity in Bornean frogs.'' The Natural History Journal of Chulalongkorn University, 3(1), 9-15.
Inger, R. F. and Bacon, J. P. (1968). ''Annual reproduction and clutch size in rain forest frogs from Sarawak.'' Copeia, 1968, 602-606.
Inger, R. F. and Stuebing, R. B. (2005). A Field Guide to the Frogs of Borneo, 2nd edition. Natural History Publications (Borneo), Kota Kinabalu.
Inger, R. F., Voris, H. K., and Voris, H. H. (1974). ''Genetic variation and population ecology of some Southeast Asian frogs of the genus Bufo and Rana.'' Biochemical Genetics, 12(2), 121-145.
Iskandar, D. T. (1998). The Amphibians of Java and Bali. Research and Development Centre for Biology-LIPI, Bogor, Indonesia.
Nguyen, V. S., Ho, C. T., and Nguyen, T. Q. (2005). A Checklist of the Amphibians and Reptiles of Vietnam. Nha Xuat Ban Nong Nghiep, Hanoi, Vietnam.
Originally submitted by: Janel Marcelino (first posted 2006-04-06)
Edited by: Kellie Whittaker (2014-10-29)
Species Account Citation: AmphibiaWeb 2014 Phrynoidis asper: River Toad <https://amphibiaweb.org/species/110> University of California, Berkeley, CA, USA. Accessed Jul 2, 2022.
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Citation: AmphibiaWeb. 2022. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 2 Jul 2022.
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