Giant Asian Toad

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 (Iskandar 1998).Skin toxins from Bufo asper were able to induce the following significanteffects on mice at a dose of 100 mg/mouse: locomotor difficulties, prostration,and convulsions, with partial recovery after 5 hours. The major toxic componentin Bufo asper skin extracts is bufotalin (a bufadienolide), with a lessercomponent of resibufogenin and minor amounts of other bufadienolides andbufotoxins (Daly et al. 2004). The diploid chromosome number is 22, with five pairs of large chromosomes andsix pairs of smaller chromosomes (Iskandar 1998).

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).

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 (Iskandar 1998). 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 (Inger 2003).

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).

This frog is consumed for food in Sabah and peninsular Malaysia (IUCN 2006).

Phrynoidis aspera, the giant Asian toad, inhabits primary and old secondary rainforests of Indonesia, Malaysia, Thailand, Myanmar and Borneo up to 1500 m above sea level and in Vietnam at about 700 m in elevation. Although not yet reported from Cambodia and Laos, it is likely also to occur in these countries. Phrynoidis aspera lives along banks of small to medium-sized streams and large rivers. It goes by various other common names including River Toad, Rough Toad, Kodok Buduk Sungal, Kodok Puru Besar.

The giant Asian toad has a large and stout body. Female snout-vent length measures 95-140 mm, and males 70-100 mm. Their rough skin is usually dark brown, gray or black in color and covered with warts or tubercles. The white belly has black spotting. These toads have a broad and blunt head, without bony crests, and have a visible tympanum. Males have blackish coloring on their throats and nuptial pads on the base of the first finger.

Phrynoidis aspera is nocturnal and partially aquatic, coming out at night and hiding under submerged stones during the day.It lives along stream banks rarely straying more than 2 meters (6 feet) from the water's edge.Males call to females from widely spaced sites along the stream banks at night, particularly when there is a full moon. The call is a raspy chirp, sometimes repeated.They do not form choruses.

Adults do not move much on a given day. However, research has found adult toads move distances of up to 465 meters over a period of 180 days.Inger (2003) hypothesizes that slow net movement allowed Phrynoidis aspera to disperse between the continent and Borneo over relatively short periods of sea regression during the Pleistocene.

The giant Asian toad reproduces year-round. Females lay huge clutches, with an average size of 12,792 eggs per clutch, in quiet portions of streams. Ripe ova have a diameter of 1.26 mm. The dark-colored tadpoles reach 12-15 mm before metamorphosis.They are somewhat flattened, with a leaf-shaped tail. Tadpoles typically adhere to the bottom of streams with slow to medium currents using their subterminal, cuplike mouths. Their enlarged lips enable bottom feeding.

Phrynoidis aspera is somewhat resilient to habitat loss and pollution, surviving where other frogs have disappeared in Sumatra and Java.It is listed as “of least concern” by the IUCN.However it occurs in varying abundances in different parts of its range and shows low genetic diversity in fragmented Malaysian forest, especially compared with other Phrynoidis species.

Giant Asian toads have large parotoid glands located behind their eyes.These secrete a toxic, white milk to deter predators when the toads get agitated.Skin toxins from Phrynoidis aspera induce locomotor difficulties, prostration, and convulsions in mice, with partial recovery after 5 hours. The major toxic component in Phrynoidis aspera skin extracts is bufotalin (a bufadienolide), with a lesser component of resibufogenin and minor amounts of other bufadienolides and bufotoxins.

This frog is eaten by people in Sabah and peninsular Malaysia.

(Marcelino and Whittaker 2014; IUCN SSC Amphibian Specialist Group 2014; Inger 2003;)

The Asian giant toad (Phrynoidis asper), sometimes referred to as the river toad, is a species of true toad native to Mainland Southeast Asia and the Greater Sundas. It is a medium-large toad, but it is easily confused with its larger relative, the giant river toad (P. juxtasper).