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; ParliamentNT
Tabled by Delia Lawrie
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Dr Freeland Written Submissions Cane Toad Inquiry Report Volume 2 152 range. This seems to have been highly successful. The Territory also began production of brochures providing the public with the capacity to identify toads, urging them to take steps not to unwittingly move toads about in their vehicles and equipment and to call the Commission should they believe they had found a toad. These policies continue to this day. The research effort was structured to support the development of a national effort and was composed of Phase 1: quantification of the rate of spread so as to allow prediction of the time likely to expire prior to the toad's conquest of various parts of the Territory; description of cane toad populations across a broad span of times from initial colonisation to determine if the populations underwent massive growth and decline phases, whether colonising toads were of large size and whether east coast toads were skinny; could the above patterns be explained by food availability or parasitism?; were urban east coast toads similar to those in rural areas?; and Phase 2 were there significant impacts on frog communities around billabongs in the dry season (the time of greatest likelihood of strong competition for food?; what were the impacts on the Northern Quoll? were there impacts on communities of ground dwelling arthropods?; did the behaviour of metamorphling cane toads render them vulnerable to possible control measures?; what were the habitat preferences of native frog and cane toad tadpoles i.e. what was the likelihood of there being negative interactions at the larval phase?; what were the impacts on goanna populations?; and what were the impacts on freshwater crocodiles?. The Territory's Phase 1 research. provided a good indicator of natural rates of colonisation (accurate to the Roper River where human assisted transportation clearly intervened to speed the process e.g. predicted date of colonising Katherine was 2003 yet it arrived there in 1999); demonstrated that the hypothesised growth and decline phases of colonising populations did not occur within 19 years of colonisation; revealed a similar absence of temporal pattern in body size; clearly indicated that east coast toads were skinny and lived in depleted populations; and demonstrated that the patterns could not be explained by food availability or parasitism by single or multi-celled parasites. Subsequent study of a single population over 12 years has since shown there was no consistent temporal pattern in population density or body condition. Both population size and body condition fluctuated wildly (Attachment 3). Population density was dictated by wet season (especially December) rainfall while body condition was related to rainfall during May to June. More December rains resulted in more toads in the dry season, and toads were fatter with more rain in May-June.