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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Written Submissions Dr Brown Volume 2 Cane Toad Inquiry Report 145 SUBMISSION NO. 21 Dr Greg Brown, University of Sydney, School of Biological Sciences PO Box 441 HUMPTY DOO NT 0836 Executive Officer Sessional Committee on Environment and Sustainable Development re: Cane Toad Inquiry Public Hearing Dear Sir Belatedly here is a written copy of my submission to the cane toad committee. Greg Brown SUBMISSION TO THE INQUIRY INTO ISSUES ASSOCIATED WITH THE PROGRESSIVE ENTRY INTO THE NORTHERN TERRITORY OF CANE TOADS The research group that I am associated with, headed by Professor Rick Shine, has been awarded a 5-year grant by the Australian Research Council to study the effect of cane toads on reptile populations in the Top End. Our goal is not to find a means of controlling toads but rather to document the ecological effects that toads have on native animals. Over several decades, cane toads have spread hundreds of kilometres across Australia yet biologists have little idea of what effect they have on native animal populations. Anecdotal reports abound, though, and these suggest that snakes and lizards become noticeably rare or even disappear after the arrival of toads. We hope to carefully document what happens to reptile populations following the cane toad invasion into the Top End and detail, for the first time, the ecological impact of a novel toxic prey item on its predators. As the toads continue to expand other localities may then have a better idea of what they can expect. We received Commonwealth funding for this study because we have been conducting long-term mark recapture studies on various reptile populations (water python, death adder, keelback snake, slatey-grey snake, Macleays water snake, file snake and snakenecked turtle), mainly around Fogg Dam, for the last 5 to 10 years. These studies have provided detailed information on the sizes of the populations, their age structures, reproductive rates, growth rates etc. Because the studies have been going on for such a long period we also have an understanding of how population parameters vary seasonally and from year to year. Thus, we have a good deal of 'background' information to which we can compare any changes observed after the arrival of toads. At present, there are 10's of thousands of individually marked snakes on the Adelaide River floodplain. Many of these snakes were first marked as babies and have been recaptured and released repeatedly over the years. We have followed their movements, growth rates and reproduction over most of their lives. For some individuals we can trace though three generations of their family and identify their parents and siblings. And now we are waiting to see what will happen to them when they encounter a novel and deadly toxic prey item.