AbstractKakadu National Park is nationally and internationally recognised for its natural and cultural heritage assets, including its exceptional biodiversity. In recent years, there has been growing evidence to suggest that elements of Kakadu's biodiversity, particularly the small-medium sized mammals, may be undergoing substantial change. In this thesis I seek to investigate further the extent and magnitude of these changes. I also explore the role of a number of key threatening processes (fire regimes, feral cats and cane toads) in these changes. Finally I give detailed consideration to the current biodiversity monitoring programs in Kakadu National Park, the appropriateness and adequacy of these programs and how they can be improved to better inform management in the future.
Changes in mammal populations were originally identified at the Kapalga Research Station in the north of the Park. Significant and rapid declines were recorded for a range of taxa including rodents, dasyurids, possums and the only bandicoot species known to occur there. During this study I have demonstrated that mammal populations elsewhere in Kakadu are also changing, but the species involved and the direction and magnitude of these changes is not uniform. I have found that some species, such as the Arnhem rock rat, appear to be declining across the Park and these species need to be the focus of dedicated conservation programs in the future. I have also shown that fire regimes are an important determinant of the distribution and abundance of some mammal species in Kakadu and that the current regimes in Kakadu are contributing to at least some of the observed changes in mammal populations. In addition I have demonstrated the short term impacts of cane toad colonisation on biodiversity in the Park, and have provided a preliminary assessment of the distribution and density of feral cats in the Park, both key threatening processes that continue to demand further consideration as part of attempts to address the current changes in mammal status in Kakadu and the region more broadly.
Prior to the commencement of this study the extent and cause of changes in mammal populations were unclear. As a result the response from management was delayed and generally non-strategic. A primary reason for the uncertainty in both cases was the lack of ongoing information about the status of mammal populations (and biodiversity in general) over time, and the factors affecting it. The absence of monitoring programs that could provide this information has been a fundamental hurdle to the management and conservation of biodiversity in the Park. I propose in this thesis that current monitoring programs (of which there are few) need to be expanded and enhanced to provide management with adequate and robust information about biodiversity (and particularly threatened species and those undergoing change such as small mammals) and how that biodiversity is affected by key threatening processes and management programs
|Date of Award
|John Woinarski (Supervisor), Peter Whitehead (Supervisor) & Stephen Garnett (Supervisor)