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Survey of a population of Black-spined Toad Bufo melanostictus in Timor-Leste: confirming identity, distribution, abundance and impacts of an invasive and toxic toad

Trainor, Colin R. (2009). Survey of a population of Black-spined Toad Bufo melanostictus in Timor-Leste: confirming identity, distribution, abundance and impacts of an invasive and toxic toad. Darwin, NT: Charles Darwin University.

Document type: Research Report
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Author Trainor, Colin R.
Title of Report Survey of a population of Black-spined Toad Bufo melanostictus in Timor-Leste: confirming identity, distribution, abundance and impacts of an invasive and toxic toad
Publication Date 2009
Publisher Charles Darwin University
Place of Publication Darwin, NT
Total Pages 49
Field of Research 300800 Environmental Sciences
Abstract
EXECUTIVE SUMMARY
IDENTITY

All toads (945 individuals on 25.8 km of walked transects) observed in Dili, Liquica,Covalima (Suai), Manufahi (Same), Bobonaro and Oecusse districts were Black-spinedToad Bufo melanostictus . No Cane Toad B. marinus were recorded, and this species hasnot yet been recorded for Timor-Leste or Timor island. The Black-spined Toad issuperficially similar to the Cane Toad in appearance (and general ecology where known)and resources for the Timor-Leste government and other organisations to confidentlyidentify toads and other frogs are limited in Timor-Leste.
ORIGINS
The Black-spined Toad is native to Pakistan, India through to Indonesia. Populations aresilently invading eastern Indonesian islands (including Bali, Lombok, Sulawesi and Papua)through human transport. The international land border with Indonesian West Timor isentirely porous, and toad populations presumably entered from West Timor (or entereddirectly from boat transport originating from western Indonesia). The Black-spined Toadhas never been recorded on the Australian mainland, though a few individuals have beendetected on shipping containers by Australian Quarantine and Inspection Service (AQIS)entering Australia from eastern Indonesian. The Black-spined Toad is very poorly-studiedcompared to the Cane Toad, and its transport through the biologically diverse andendemic-rich Wallacean region (including Timor) is causing unnoticed and broad scalechanges to some biodiversity elements. Notably, a second species of invasive toad(Indonesian Toad B. biporcatus) has recently been recorded on Roti island off Timor.
EXTENT OF THE POPULATION
The Black-spined Toad occurs widely in western Timor-Leste (all districts, allanthropogenic habitats), and has been recorded as far east as Viqueque district. Populationsare invading faster, and occur at higher densities, along the higher rainfall south coast. Onthe north coast, toads are present in Dili (arriving about 2007), and are currently absentfrom Manatuto (town), Baucau and Los Palos. There are no reports yet from Atauro island.
POTENTIAL POPULATION EXPANSION
The Black-spined Toad tolerates a wide climatic range and is capable of establishing populations throughout Timor-Leste. Population growth and local establishment will beinfluenced by climate, availability of wetland sites for breeding, daytime shelter and food.Populations are likely to remain small along parts of the low rainfall north coast (e.g.Manatuto town c. 600 mm rainfall/year), and the tops of mountains will be sub-optimal  (e.g. currently absent from mountain areas near Maubisse at 1,700 m). Toads are likely toreach the remaining eastern districts during the next 3-15 months (next 1-2 wet seasons).
ENVIRONMENTAL AND OTHER IMPACTS
The Black-spined Toad has toxins in parotid glands on its back. Frogs are widely eaten byvillagers in Timor-Leste, and at least one child has been killed, and many others have become sick after eating toads. The toad is a public health issue because local villagerslack knowledge about the toad’s toxicity. It is also a nuisance because toads can enter wells, drown and rot, potentially polluting important water sources. Road-killed toadswhich rot and smell will also be a nuisance particularly during the wet season. Wecollected qualitative data on the impact of the toads on Timor-Leste’s terrestrial biodiversity. Reportedly the Green Pit Viper Trimesurus insularis (a common poisonoussnake on Timor), the Timor Monitor  Varanus timorensis (a small monitor lizard), other snakes, and quail/buttonquail species (small birds that nest on the ground) have declinedsince arrival of the toad. Preliminary observations suggest that populations of raptors (e.g.Brahminy Kite, Short-toed Eagle, Black Kite and Spotted Kestrel) have not been impacted.Some may not eat toads, while others are immune to the toxins. Populations of scincidlizards, geckos, land snails (including island endemics) and some other insect groups may be impacted by direct toad predation. Impacts to agriculture are poorly known – livestock such as buffalo, cattle, pigs, goats and chickens do not appear to be affected by toads.Recently hatched chickens (chicks) do die after ingesting toad toxin typically from road-killed toads. The impact of toads on crop pests (e.g. locusts, caterpillars) is unknown.Villagers indicated that toads ate the young shoots of maize, an important staple crop, butwe were unable to confirm this information.
RECOMMENDATIONS
• A public awareness campaign (radio, TV, poster/sticker, visits to all districts andAtauro island) is urgently needed (late 2009 and early 2010) to disseminateinformation to the public on the status of the toad, and particularly to warn villagersnot to eat toads because of its toxicity. It would be of value to disseminate informationon the design of wells to reduce Toad pollution/nuisance.
• Survey of eastern districts (Manututo, Baucau, Viqueque and Lautem) and Atauroisland is needed to better understand the current status of the toad.
• A fauna survey is needed to generate quantitative data on the impact of the toad on thehighly endemic and vulnerable island biodiversity of Timor-Leste including birds,mammals, reptiles, frogs, and some invertebrate groups.
• Australian government (e.g. AQIS) to provide training/support in quarantine procedures for invasive toads and other to minimise the risk of invasive alien(non-native) species, including but not limited to Cane Toad and Indonesian Toad,entering the country.
• Ministry of Agriculture and Fisheries to establish collaborative research programs withother research organisations to further develop research skills and generate reliableinformation on identity and status of invasive and native wildlife.
• Prepare identification materials (or encourage international support for the generatingidentification materials and publication) for frogs and toads in Timor-Leste, whichwould be of value for public education and awareness, and identification during faunasurveys, impact assessments and Timor-Leste university research.



Additional Notes A report by Charles Darwin University to AusAID under contract agreement NO.52294
 
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Created: Tue, 16 Mar 2010, 14:31:21 CST by Sarena Wegener