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
Tabled Paper 1123
Tabled Papers for 9th Assembly 2001 - 2005; Tabled papers for 9th Assembly 2001 - 2005; Tabled Papers; ParliamentNT
Tabled by Delia Lawrie
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Dr Freeland Written Submissions Cane Toad Inquiry Report Volume 2 158 mortality or debilitation of cane toads such that cane toad populations were reduced to levels that eliminate at least the most serious impacts on the native fauna. RESEARCHES THAT COULD BE UNDERTAKEN One of the few certainties about the cane toad's invasion is that there is no shortage of individuals who seek funding for their private research from government nature conservation agencies, or even employees of government agencies who seek to justify their activities on the basis of dealing with the cane toad invasion. The determination of which, or any of the proposed researches are to be funded requires a sound understanding of what is known about cane toads, what can be learnt from what kinds of research, and whether the things we can learn are in any way helpful to our management of cane toad populations or the public response to the invasion. The following things are know about the cane toad's impact on nature (and I do not believe these things to be controversial in any manner). Cane toads impact heavily (perhaps leading to extinction) on populations of the Northern Quoll. Cane toads are toxic to and hence can kill a variety of native animals. Cane toads eat large numbers of prey items, particularly insects. Cane toads may reduce the size of some native populations. Cane toads are likely to cause the extinction of at least one species of proteocephalid tapeworm and in consequence there may be destabilisation of some frog communities. Cane toads appear to severely impact on populations of some large bodied goanna species, but these populations appear to recover. Cane toads kill some freshwater crocodiles yet they persist in large populations in areas where there are cane toads, and are known to successfully consume cane toads in nature. The vast majority of the Territory's species will persist following cane toad invasion. In determining research priorities it is critical to remember that no matter how many resources are channelled into the effort, it is impossible to ever know the truth about the cane toad's past or future impacts on the vast majority of the thousands and thousands of native species present in the Northern Territory (and it is inevitable that there will be many). The prioritisation is about determining which impacts and species will be investigated and which control mechanisms deserve more serious treatment. Investigating Impacts: Broad-scale biological surveys and efforts to monitor ecological communities are the primary mechanisms used to date to estimate cane toad impacts (e.g. Catling et al., 1999; Watson and Woinarski 2003).There are major difficulties associated with these types of assessment (see discussions in Watson and Woinarski 2003). They centre on the inherent temporal/spatial variability of natural populations, the confounding influence of patchy temporal and spatial occurrence of fire, weeds and feral animals other than cane toads (uncontrolled confounding variables), frequently very small samples sizes for many species, the statistical difficulty of dealing with multiple analyses of many species from the same data set (i.e. Type 1 Error = falsely accepting an impact when one does not exist), and the standard, fixed quadrat approach allowing assessments of only the sampled quadrats rather than providing statistical applicability to the area as a whole. A good example of the vagaries of weather and possibly other variables in confounding our understanding of possible cane toad impacts is the frog call monitoring project