Research and management to reverse the decline of native mammal fauna

This project sought to characterise the conservation status of the mammal fauna in northern Australia, investigate factors that may be implicated in the decline of this fauna, and identify effective management responses.

The current rate and severity of decline of the mammal fauna in at least parts of northern Australia is exceptional, with analysis indicating that it exceeds that elsewhere in Australia. This is of considerable conservation concern because northern Australia has previously experienced relatively little loss of biodiversity (since European settlement) and has acted as a refuge for many species and species-groups that have exhibited substantial declines elsewhere in Australia. The current declines in the mammal fauna in northern Australia are also exceptional in a global context, because most declines and extinctions elsewhere in the world have occurred in areas affected by substantial land clearing, habitat modification or hunting, issues that are not (yet) major concerns in northern Australia. A notable feature of the decline of mammals in northern Australia is that declines have been reported from some large and relatively well-resourced conservation reserves, indicating that reservation alone has been insufficient to maintain biodiversity and that the intensity, scope or approach of management in reserves may need substantial refinement.

This project comprised multiple components, including:

  • trialling two 64 cat exclosures in Kakadu National Park to monitor the response of native mammal populations in the absence of cats;
  • monitoring the impact of cat predation on the survival of introduced mammals in small-scale cat exclosures;
  • ongoing monitoring of mammals at Kakadu, Litchfield, Nitmiluk and Garig Gunak Barlu National Parks, plus AWC’s Mornington, Marion Downs, Tableland, and Wongalara Wildlife Sanctuaries. Mammal trends were correlated with other environmental pressures at the sites such as fire patterns and the amount of grazing stock;
  • an investigation into the types and levels of disease amongst mammals at a number of sites.
  • a broad scale assessment of the abundance of feral cats through extensive remote camera surveys, and of diet through stomach content analysis;
  • a study of the behaviour (including response to fire and grazing intensity) and abundance of feral cats though radio-tracking;
  • a study of the survival (and causes of mortality) of selected mammal species, at sites with varying fire regimes;
  • a study into the effectiveness of using taste aversion training to aid the conservation of quolls by training them not to eat cane toads;
  • an assessment of the effectiveness of taste-aversion training for floodplain monitors in response to cane toad invasion of the Kimberley;
  • comprehensive overview of the conservation status of all Australian mammal species; and
  • collaborative development of a conservation strategy for threatened species in Kakadu with Parks Australia.

Study components demonstrated that predation by feral cats caused local extinction of an experimentally reintroduced population of a native mammal species, and that feral cat impacts were much more severe in areas that had been extensively burnt; but a cat exclosure fencing study in Kakadu failed to demonstrate beneficial response by native mammals, possibly because the study period was too brief and mammal populations in the area were too depleted.

Mammal surveys across combinations of fire and grazing treatments in the Kimberley showed that the benefits of improving fire patterns to mammal richness and abundance were significantly muted if introduced herbivores were present.

The first substantial assessment of the incidence of disease in mammal assemblages of northern Australia indicates the presence of some pathogens that may have lethal or sub-lethal impacts on native mammals, but there is uncertainty around their role in the current decline.

The research took place in Kakadu, Garig Gunak Barlu and Litchfield National Parks, on the Tiwi Islands in the Northern Territory, at Australian Wildlife Conservancy properties in the Kimberley, Northern Territory and Cape York and in the Balangarra Indigenous Protected Area.

Rapid increase of Australian tropical savanna reptile abundance following exclusion of feral cats

Stokeld D, Fisher A, Gentles T, Hill BM, Woinarski JCZ, Young S & Gillespie GR. 2018. Rapid increase of Australian tropical savanna reptile abundance following exclusion of feral cats. Biological Conservation 225: 213-221. https://doi.org/10.1016/j.biocon.2018.06.025.

What do predator diets tell us about mammal declines in Kakadu National Park?
Multiple cameras required to reliably detect feral cats in northern Australia tropical savanna: an evaluation of sampling design when using camera traps (journal article)
Variation in body condition indices of crimson finches by sex, breeding stage, age, time of day, and year

Conservation Physiology, Milenkaya, O, Weinstein, N, Legge, S, Walters, J, 2013

Ongoing unraveling of a continental fauna: Decline and extinction of Australian mammals since European settlement
Monitoring indicates greater resilience for birds than for mammals in Kakadu National Park, northern Australia.
Conservation of the Patchily Distributed and Declining Purple-Crowned Fairy-Wren (Malurus coronatus coronatus) across a Vast Landscape: The Need for a Collaborative Landscape-Scale Approach
Evaluating the status of species using Indigenous knowledge: novel evidence for major native mammal declines in northern Australia
The illusion of nature: perception and the reality of natural landscapes, as illustrated by vertebrate fauna in the Northern Territory, Australia

Ecological Management and Restoration, Woinarski, JCZ, 01/2014

The impacts of fire on birds in Australia’s tropical savannas

Emu, Woinarski, JCZ, Legge, S, 09/2013

Fire management in the central Kimberley (EcoFire): delivering measurable results by integrating science and land management in a cost-effective model

Innovation for 21st Century Conservation, Legge, S, Fleming, A, ISBN: 978-0-9871654-1-1

Improving biodiversity monitoring

Austral Ecology, Lindenmayer, D, Gibbons, P, Bourke, M, Dickman, CR, Ferrier, S, Fitzsimons, J, Freudenberger, D, Garnett, S, Groves, C, Hobbs, R, Kingsford, RT, Krebs, C, Legge, S, Lowe, AJ, McLean, R, Possingham, H, Radford, J, Robinson, D, Thomas, D, Varcoe, T, Vardon, M, Wardle, G, Woinarski, J, Zerger, A, 05/2012

Inferring population connectivity across the range of the purple-crowned fairy-wren (Malurus coronatus) from mitochondrial DNA and morphology: implications for conservation management

Australian Journal of Zoology, Legge, S, Skroblin, A, Lanfear, R, Cockburn, A, 2012

MODIS time series as a tool for monitoring savanna bird diversity

International Journal of Wildland Fire 2012

Prioritizing threat management for biodiversity conservation

Conservation Letters, Cawardine, J, O'Connor, T, Legge, S, Mackey, B, Possingham, HP, T.G., M

Ongoing unraveling of a continental fauna: Decline and extinction of Australian mammals since European settlement

PNAS, Woinarski, JCZ, Burbidge, AA, Harrison, PL, 02/2015

Is disease contributing to terrestrial mammal declines in Australia’s Top End?

Wildlife Disease Association Australasian Section Annual Conference, 29 September - 4 October 2013, Reiss, A, Warren, K, Gillespie, G, Jackson, B, Skerrat, L, Brennan, K, Stokeld, D

Critical-weight-range marsupials in northern Australia are declining: a commentary on Fisher et al. (2014) ‘The current decline of tropical marsupials in Australia: is history repeating?’

Global Ecology and Biogeography, Woinarski, JCZ, 2014

The current decline of tropical marsupials in Australia: Is history repeating?

Global Ecology and Biogeography , Fisher, DO, Johnson, CN, Lawes, MJ, Fritz, SA, McCallum, H, Blomberg, SP, VanDerWal, J, Abbott, B, Frank, A, Legge, S, Letnic, M, Thomas, CR, Fisher, A, Gordon, IJ, Kutt, A, 02/2014

Guide to Threatened species of Kakadu National Park

The project was led by Dr Graeme Gillespie, with researchers from Charles Darwin University, the Australian Wildlife Conservancy, the Northern Territory Department of Land Resource Management, University of Sydney, the University of Technology Sydney and Murdoch University.  The team received valuable assistance from Parks Australia, Kakakadu Traditional Owners, the Tiwi Land Rangers and Balangarra Rangers.

Project Leader:
Dr Graeme Gillespie
Department of Land Resource Management
Northern Territory Government
[email protected]
08 8995 5025