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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



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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Tabled Paper 1123


Tabled Papers for 9th Assembly 2001 - 2005; Tabled Papers; ParliamentNT




Tabled by Delia Lawrie


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Written Submissions ERISS Kakadu Report 2002 Volume 2 Cane Toad Inquiry Report 43 The issue of potential impacts of cane toads on granivorous prey insects and resultant repercussions on Kakadu's native plants has been raised, although this is highly speculative. There is evidence, for example, that high densities of harvester ants can significantly reduce the density of speargrass (Sorghum intrans). In terms of plant-animal interactions, it is possible that subtle ecological changes could occur amongst other biota, and other flow-on effects. Feral cats and pigs have been known to die from mouthing or ingesting cane toads. These animals cause damage to the native fauna and landscape of Kakadu, and any decline in their numbers would be considered a benefit. The reduction in numbers of predators such as varanids (goannas) and snakes could be of benefit to the several species of ground-dwelling/nesting birds in Kakadu, in addition to crocodiles and turtles whose eggs are preyed upon by other large reptiles. Cane toads are known to feed on human faeces, and as a result they may harbour human strains of Salmonella and other bacteria. The eggs of human parasites are also spread via toad faeces. In areas where modem sanitation practices are lacking, the presence of large numbers of cane toads could represent a health hazard. Another health-related issue is the potential for substance abuse of the cane toad toxin, a habit forming practice that is established in northern Queensland and in countries such as Fiji. Identification of the risk The data on cane toad effects, distribution and densities are mostly inconclusive and/or show great variability. In addition, information on distributions and abundance of Kakadu animal species are deficient. Nevertheless, it is still possible to identify key habitats and also prioritise particular species based on the likelihood that they will be at greater risk from cane toads than other species, and their importance to the ecological and/or cultural values of Kakadu. Identification of key habitats Aquatic stages In Kakadu. cane toads will breed in both temporary and permanent waterbodies and so their Aquatic stages will be found in a variety of aquatic habitats. They will concentrate their breeding activity during the wetter periods, although they are also known to breed during the Dry season. During the Wet season, when many of the major wetland habitats are inundated, cane toad breeding may be concentrated in the wetland habitats associated with the open forests and woodlands of the lowland plains. Terrestrial stages As the Dry season progresses, cane toads will move progressively from sites of temporary water to permanent water. The floodplains and sheltered habitats on the margins of floodplains and temporary or shallow billabongs will provide ideal cane toad habitat during the early to mid Dry season. The late Dry season will see high densities of cane toads near permanent water or moisture, including permanent billabongs and patches of monsoon rainforest. The Wet season will probably see the highest numbers of cane toad metamorphlings, mainly around the moist margins of the waterbodies they emerged from. Wet season inundation of the major wetlands habitats will see