Duttaphrynus melanostictus (Schneider, 1799)
Kaiser, Hinrich, Carvalho, Venancio Lopes, Ceballos, Jester, Freed, Paul, Heacox, Scott, Lester, Barbara, Richards, Stephen J., Trainor, Colin R., Sanchez, Caitlin & O'Shea, Mark, 2011, The herpetofauna of Timor-Leste: a first report, ZooKeys 109, pp. 19-86 : 26-28
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|Duttaphrynus melanostictus (Schneider, 1799)|
(E) Black-spined Toad, Common Asian Toad, Common Sunda Toad. (T) Manduku Interfet (manduku = frog, INTERFET = International Force for East Timor; see below).
This toad can be recognized by its stout body, dry and warty skin, and by the distinct pattern of bony ridges (cranial crests) on the head. The shape and color of these ridges are characters useful for distinguishing among different toad species. In Duttaphrynus melanostictus they are of varying thickness and include a canthal ridge, supralabial ridge, and a series of ridges framing the eye (preorbital, supraorbital, postorbital, and orbito-tympanic ridges; Fig. 3 View Figure 3 ). The tops of these ridges are usually black. A second important and useful characteristic to differentiate between toad species is the size and shape of the large parotoid gland (sometimes also described as a “poison” gland) on either side of the head. In Duttaphrynus melanostictus this gland is elongate and about 2½ -3 times the size of the eye ( Fig. 3 View Figure 3 ). This species of toad also usually has several protruding wart-like skin glands on its back behind its head in addition to many smaller glands all over its body, most of which are tipped with black. Our familiarity with the species from elsewhere in the region allows us to confirm its identity.
Collection and natural history.
Hiding under a diverse array of objects by day and active by night, this toad is a relatively recent invader of Timor-Leste (see Trainor 2009), yet it was one of the most commonly encountered amphibians where it occurred. The distribution of Duttaphrynus melanostictus in Timor-Leste currently excludes areas of high elevation (above ca. 1200 m) as well as the region east of a line connecting Manatuto and Viqueque ( Trainor 2009). We collected five voucher specimens at night (e.g., on the path leading to the Trilolo River north of Same, Manufahi District, altitude 553 m) and noted the presence of this species in disturbed habitats (e.g., towns, roadsides), cultivated habitats (e.g., coffee plantations) and some fairly pristine habitats (e.g., coastal scrub). Individuals ranged from tadpoles and juveniles (though not recent metamorphs) to adults and they exhibited varying shades of dull yellow to brown coloration. This is the only species of true toad reported from Timor-Leste so far, but we have been unable to verify the presence of specimens from Timor in herpetological collections. Therefore, our records appear to be the first vouchered confirmation of this species for Timor-Leste and Timor.
Reports by Australian peacekeepers of the cane toad, Rhinella marina , in Timor-Leste are an error arising from the soldiers’ familiarity with Rhinella marina , the only bufonid introduced to Australia and New Guinea, and their lack of familiarity with the Asian Duttaphrynus melanostictus . It is interesting in this regard that this species has taken on the Tetun name of the International Force for East Timor (INTERFET), the transitional peacekeeping force that arrived to stabilize the country after the departure of the Indonesian occupation force. INTERFET was composed primarily of Australian peacekeepers and the local belief, based on the erroneous identification of Duttaphrynus melanostictus by these personnel, is that INTERFET is responsible for the presence of this toad in Timor-Leste. The distribution of Duttaphrynus melanostictus includes several other Lesser Sunda Islands (e.g., Bali, Lombok), and it may be impossible to ascertain from where and when the initial wave of toad invasion originated.
The introduction of toads to non-native environments has frequently resulted in ecological disasters. The most notorious example of this has been the cane toad ( Rhinella marina ), whose spread by humans has become a problem with nearly global implications (e.g., Covacevich and Archer 1975; Lever 2001; Phillips et al. 2007). The species has been carried from its native northern South American habitat to locations as widespread as the Greater and Lesser Antilles, Florida, Hawaii, the Fiji Islands, the Philippines, Taiwan, the Ryukyu Island Archipelago of Japan, several Pacific islands, New Guinea, and, famously, Australia (see Zug and Zug 1979). It appears that the spread of Duttaphrynus melanostictus may rank a close second in terms of its geographic reach (from the Indian subcontinent throughout mainland and insular Southeast Asia), though perhaps not in terms of its ecological significance (e.g., Inger and Voris 2001). However, toads are voracious opportunistic predators whose impact on a newly colonized ecosystem may take years to assess. Reported impacts include alteration of the food chain, detrimental effects on lizard population recruitment, extirpation of leaf litter amphibians and their tadpoles, reduction of amphibiophagous reptile and mammal densities, and even poisoning of human or canid predators (e.g., Trainor 2009). We have recommended to government agencies that the advance of Duttaphrynus melanostictus in Timor-Leste requires close monitoring and a popular campaign to avoid human injury. A second toad invasion appears to be underway concurrently by Ingerophrynus biporcatus (formerly Bufo biporcatus ) on Roti Island, an island neighboring Timor ( Trainor 2009).
A simple distinction between Duttaphrynus melanostictus and Rhinella marina can be made by looking at the morphology of features described above. Whereas Duttaphrynus melanostictus has an elongated parotoid gland that is about three times the size of the eye ( Fig. 3 View Figure 3 ), the gland of Rhinella marina is considerably larger (nearly five times the size of the eye) and shaped like an irregular rectangle with rounded corners. The cranial crests of Duttaphrynus melanostictus are relatively thin and topped with black, whereas those of Rhinella marina are rather stout, surround the eye and are colored as the rest of the head.
Prior to the revision of amphibian taxonomy by Frost et al. (2006), this species was known as Bufo melanostictus .
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