Sessional Committee on Environment and Sustainable Development Written Submissions Received Volume 2 Issues associated with the progressive entry into the Northern Territory of Cane Toads October 2003
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Written Submissions Parks & Wildlife Commission NT Volume 2 Cane Toad Inquiry Report 31 SUBMISSION NO. 1B Parks and Wildlife Commission of the Northern Territory Ms Jailee Wilson Submitted: 30 May 2003 RISKS AND POTENTIAL EXTENT IN THE NT Cane toads (Bufo marinus) were introduced into eastern Queensland in 1935 and spread into the Northern Territory in 1982/83. Potential Extent Cane toads reached the Northern Territory (Nicholson River drainage) in 1982/83 and annual expansion of range since then has been estimated at about 30km/year. However, they appear to have spread more rapidly than this over the last 3-4 years, presumably because they have breached the large river drainages of the Top End. They have now colonised most of Arnhem Land, some of the Pellew Islands, the southern half of Kakadu NP and Katherine. The current invasion front extends from Ramingining and Pine Creek in the north, Victoria River Crossing in the west and Dunmarra in the south. At current rates, toads will colonise Darwin in the wet season of 2003/04. All of the mainland Top End is likely to be colonised by the end of 2004. Their potential distribution in Australia, based on suitability of climatic conditions, is shown below (Sutherst et al. 1996). The expanding distribution of the cane toads is being documented on the Frogwatch website (www.frogwatch.org.au). Impacts on native fauna There has been considerable dispute about the ecological impacts of cane toads, fuelled partly by the previous lack of comprehensive monitoring of wildlife populations. The most recent major review of potential impacts was by the Office of the Supervising Scientist (Van Dam et al. 2002). Of 151 predator species assessed 10 species were considered likely to be at risk, 12 species were considered at possible risk and the risk for 98 species were considered uncertain. Almost all authorities recognise substantial short-term impacts - an initial major decline of many vertebrate predators (especially including goannas, most snakes and northern quoll, but also including some crocodiles, turtles, fish and birds),