Wildlife Research Wildlife Research Society
Ecology, management and conservation in natural and modified habitats

Monitoring indicates rapid and severe decline of native small mammals in Kakadu National Park, northern Australia

J. C. Z. Woinarski A B E , M. Armstrong A , K. Brennan A , A. Fisher A , A. D. Griffiths A , B. Hill A , D. J. Milne A , C. Palmer A , S. Ward A , M. Watson A C , S. Winderlich D and S. Young A

A Department of Natural Resources, Environment, The Arts and Sport, PO Box 496, Palmerston, NT 0831, Australia.

B School for Environmental Research, Charles Darwin University, Casuarina, NT 0909, Australia.

C Present address: PO Box 601, Jabiru, NT 0886, Australia.

D Kakadu National Park, PO Box 71, Jabiru, NT 0886, Australia.

E Corresponding author. Email: john.woinarski@nt.gov.au

Wildlife Research 37(2) 116-126 http://dx.doi.org/10.1071/WR09125
Submitted: 22 July 2009  Accepted: 3 February 2010   Published: 16 April 2010


Context. Australia has a lamentable history of mammal extinctions. Until recently, the mammal fauna of northern Australia was presumed to have been spared such loss, and to be relatively intact and stable. However, several recent studies have suggested that this mammal fauna may be undergoing some decline, so a targeted monitoring program was established in northern Australia’s largest and best-resourced conservation reserve.

Aims. The present study aims to detect change in the native small-mammal fauna of Kakadu National Park, in the monsoonal tropics of northern Australia, over the period of 1996–2009, through an extensive monitoring program, and to consider factors that may have contributed to any observed change.

Methods. The small-mammal fauna was sampled in a consistent manner across a set of plots established to represent the environmental variation and fire regimes of Kakadu. Fifteen plots were sampled three times, 121 plots sampled twice and 39 plots once. Resampling was typically at 5-yearly intervals. Analysis used regression (of abundance against date), and Wilcoxon matched-pairs tests to assess change. For resampled plots, change in abundance of mammals was related to fire frequency in the between-sampling period.

Key results. A total of 25 small mammal species was recorded. Plot-level species richness and total abundance decreased significantly, by 54% and 71%, respectively, over the course of the study. The abundance of 10 species declined significantly, whereas no species increased in abundance significantly. The number of ‘empty’ plots increased from 13% in 1996 to 55% in 2009. For 136 plots sampled in 2001–04 and again in 2007–09, species richness declined by 65% and the total number of individuals declined by 75%. Across plots, the extent of decline increased with increasing frequency of fire. The most marked declines were for northern quoll, Dasyurus hallucatus, fawn antechinus, Antechinus bellus, northern brown bandicoot, Isoodon macrourus, common brushtail possum, Trichosurus vulpecula, and pale field-rat, Rattus tunneyi.

Conclusions. The native mammal fauna of Kakadu National Park is in rapid and severe decline. The cause(s) of this decline are not entirely clear, and may vary among species. The most plausible causes are too frequent fire, predation by feral cats and invasion by cane toads (affecting particularly one native mammal species).

Implications. The present study has demonstrated a major decline in a key conservation reserve, suggesting that the mammal fauna of northern Australia may now be undergoing a decline comparable to the losses previously occurring elsewhere in Australia. These results suggest that there is a major and urgent conservation imperative to more precisely identify, and more effectively manage, the threats to this mammal fauna.


Abbott I. 2002 Origin and spread of the cat, Felis catus, on mainland Australia, with a discussion of the magnitude of its early impact on native fauna. Wildlife Research 29 51 74 doi:10.1071/WR01011

Abbott I. 2006 Mammalian faunal collapse in Western Australia, 1875–1925: the hypothesised role of epizootic disease and a conceptual model of its origin, introduction, transmission, and spread. Australian Zoologist 33 530 561

Banfai D. S. Bowman D. M. J. S. 2006 Forty years of lowland monsoon rainforest expansion in Kakadu National Park, northern Australia. Biological Conservation 131 553 565

Begg R. J. Martin K. C. Price N. F. 1981 The small mammals of Little Nourlangie Rock, N.T. V. The effects of fire. Australian Wildlife Research 8 515 527 doi:10.1071/WR9810515

Bowman D. M. J. S. Panton W. J. 1993 Decline of Callitris intratropica R.T.Baker & H.G.Smith in the Northern Territory: implications for pre- and post-European colonization ire regimes. Journal of Biogeography 20 373 381 doi:10.2307/2845586

Bowman D. M. J. S. Price O. Whitehead P. J. Walsh A. 2001 The ‘wilderness effect’ and the decline of Callitris intratropica on the Arnhem Land Plateau, northern Australia. Australian Journal of Botany 49 665 672 doi:10.1071/BT00087

Bowman D. M. J. S. Riley J. E. Boggs G. S. Lehmann C. E. R. Prior L. D. 2008 Do feral buffalo (Bubalus bubalis) explain the increase of woody cover in savannas of Kakadu National Park, Australia? Journal of Biogeography 35 1976 1988 doi:10.1111/j.1365-2699.2008.01934.x

Bradshaw C. J. A. Field I. C. Bowman D. M. J. S. Haynes C. Brook B. W. 2007 Current and future threats from non-indigenous animal species in northern Australia: a spotlight on World Heritage Area Kakadu National Park. Wildlife Research 34 419 436 doi:10.1071/WR06056

Braithwaite R. W. Griffiths A. D. 1994 Demographic variation and range contraction in the Northern Quoll, Dasyurus hallucatus (Marsupialia: Dasyuridae). Wildlife Research 21 203 217 doi:10.1071/WR9940203

Braithwaite R. W. Griffiths A. D. 1996 The paradox of Rattus tunneyi: the endangerment of a native pest. Wildlife Research 23 1 22 doi:10.1071/WR9960001

Braithwaite R. W. Muller W. J. 1997 Rainfall, groundwater and refuges: predicting extinctions of Australian tropical mammal species. Australian Journal of Ecology 22 57 67 doi:10.1111/j.1442-9993.1997.tb00641.x

Burbidge A. A. McKenzie N. L. Brennan K. E. C. Woinarski J. C. Z. Dickman C. R. Baynes A. Gordon G. Menkhorst P. W. Robinson A. C. 2008 Conservation status and biogeography of Australia’s terrestrial mammals. Australian Journal of Zoology 56 411 422 doi:10.1071/ZO08027

Corbett L. (1995). ‘The Dingo in Australia and Asia.’ (University of New South Wales Press: Sydney.)

Corbett L. K. , Andersen A. N. , and Muller W. J. (2003). Terrestrial vertebrates. In ‘Fire in tropical savannas: the Kapalga experiment’. (Eds A. N. Andersen, G. D. Cook and R. J. Williams.) pp. 126–152. (Springer-Verlag: New York.)

Cowie I. D. Werner P. A. 1993 Alien plant species invasive in Kakadu National Park, tropical northern Australia. Biological Conservation 63 127 135 doi:10.1016/0006-3207(93)90500-Z

Doody J. S. Green B. Sims R. Rhind D. West P. Steer D. 2006 Indirect impacts of invasive cane toads (Bufo marinus) on nest predation in pignosed turtles (Carettochelys insculpta). Wildlife Research 33 349 354 doi:10.1071/WR05042

Edwards A. Kennett R. Price O. Russell-Smith J. Spiers G. Woinarski J. 2003 Monitoring the impacts of fire regimes on biodiversity in northern Australia: an example from Kakadu National Park. International Journal of Wildland Fire 12 427 440 doi:10.1071/WF03031

Finlayson C. M. Lowry J. Bellio M. G. Nou S. Pidgeon R. Waldren D. Humphrey C. Fox G. 2006 Biodiversity of the wetlands of the Kakadu region, northern Australia. Aquatic Sciences 68 374 399 doi:10.1007/s00027-006-0852-3

Firth R. S. C. Woinarski J. C. Z. Noske R. A. 2006 a Home range and den characteristics of the brush-tailed rabbit-rat (Conilurus penicillatus) in the monsoonal tropics of the Northern Territory. Australian Wildlife Research 33 397 407 doi:10.1071/WR05057

Firth R. S. C. Woinarski J. C. Z. Brennan K. G. Hempel C. 2006 b Environmental relationships of the brush-tailed rabbit-rat Conilurus penicillatus and other small mammals on the Tiwi Islands, northern Australia. Journal of Biogeography 33 1820 1837 doi:10.1111/j.1365-2699.2006.01543.x

Friend G. R. 1985 Ecological studies of a population of Antechinus bellus (Marsupialia: Dasyuridae) in tropical northern Australia. Australian Wildlife Research 12 151 162 doi:10.1071/WR9850151

Friend G. R. 1987 Population ecology of Mesembriomys gouldii (Rodentia: Muridae) in the wet–dry tropics of the Northern Territory. Australian Wildlife Research 14 293 303 doi:10.1071/WR9870293

Gill A. M. Ryan P. G. Moore P. H. R. Gibson M. 2000 Fire regimes of World Heritage Kakadu National Park, Australia. Austral Ecology 25 616 625

Griffiths A. D. McKay J. L. 2007 Cane toads reduce the abundance and site occupancy of freshwater goannas Varanus mertensi. Wildlife Research 34 609 615

Hawkins C. E. Baars C. Hesterman H. Hocking G. J. Jones M. E. et al 2006 Emerging disease and population decline of an island endemic, the Tasmanian devil Sarcophilus harrisii. Biological Conservation 131 307 324

Johnson C. (2006). ‘Australia’s Mammal Extinctions: a 50 000 Year History.’ (Cambridge University Press: Melbourne.)

Kerle J. A. 1985 Habitat preference and diet of the northern brushtail possum Trichosurus arnhemensis in the Alligator Rivers Region, N.T. Proceedings of the Ecological Society of Australia 13 161 176

Kitchener D. J. 1978 Mammals of the Ord River area, Kimberley, Western Australia. Records of the Western Australian Museum 6 189 217

Legge S. Murphy S. Heathcote J. Flaxman E. Augusteyn J. Crossman M. 2008 The short-term effects of an extensive and high-intensity fire on vertebrates in the tropical savannas of the central Kimberley, northern Australia. Wildlife Research 35 33 43

Lehmann C. E. R. Prior L. D. Williams R. J. Bowman D. M. J. S. 2008 Spatio-temporal trends in tree cover of a tropical mesic savanna are driven by landscape disturbance. Journal of Applied Ecology 45 1304 1311 doi:10.1111/j.1365-2664.2008.01496.x

Lever C. (2001). ‘The Cane Toad: The History and Ecology of a Successful Colonist.’ (Westbury Publishing: West Yorkshire, UK.)

McKenzie N. L. 1981 Mammals of the Phanerozoic south-west Kimberley, Western Australia: biogeography and recent changes. Journal of Biogeography 8 263 280 doi:10.2307/2844762

McKenzie N. L. Burbidge A. A. Baynes A. Brereton R. N. Dickman C. R. et al 2007 Analysis of factors implicated in the recent decline of Australia’s mammal fauna. Journal of Biogeography 34 597 611 doi:10.1111/j.1365-2699.2006.01639.x

Morton S. R. 1990 The impact of European settlement on the vertebrate animals of arid Australia: a conceptual model. Proceedings of the Ecological Society of Australia 16 210 213

O’Neill A. (2002). ‘Living with the Dingo.’ (Envirobook: Annandale, NSW.)

Oakwood M. 2000 Reproduction and demography of the northern quoll, Dasyurus hallucatus, in the lowland savanna of northern Australia. Australian Journal of Zoology 48 519 539

Pardon L. G. Brook B. W. Griffiths A. D. Braithwaite R. W. 2003 Determinants of survival for the northern brown bandicoot under a landscape-scale fire experiment. Journal of Animal Ecology 72 106 115 doi:10.1046/j.1365-2656.2003.00686.x

Petty A. M. Werner P. A. Lehmann C. E. R. Banfai D. S. Elliott L. P. 2007 Savanna responses to feral buffalo in Kakadu National Park, Australia. Ecological Monographs 77 441 463 doi:10.1890/06-1599.1

Phillips B. L. Brown G. P. Shine R. 2003 Assessing the potential impact of cane toads Bufo marinus on Australian snakes. Conservation Biology 17 1738 1747 doi:10.1111/j.1523-1739.2003.00353.x

Press A. J. 1988 Comparisons of the extent of fire in different land management systems in the Top End of the Northern Territory. Proceedings of the Ecological Society of Australia 15 167 175

Prior L. D. Bowman D. M. J. S. Brook B. W. 2007 Growth and survival of two north Australian relictual tree species, Allosyncarpia ternata (Myrtaceae) and Callitris intratropica (Cupressaceae). Ecological Research 22 228 236

Rankmore B. R. (2006). Impacts of habitat fragmentation on the vertebrate fauna of the tropical savannas of northern Australia; with special reference to medium-sized mammals. Ph.D. Thesis, Charles Darwin University, Darwin.

Russell-Smith J. Ryan P. G. Klessa D. Waight G. Harwood R. 1998 Fire regimes, fire-sensitive vegetation and fire management of the sandstone Arnhem Plateau, monsoonal northern Australia. Journal of Applied Ecology 35 829 846

Russell-Smith J. Ryan P. G. Cheal D. C. 2002 Fire regimes and the conservation of sandstone heath in monsoonal northern Australia: frequency, interval, patchiness. Biological Conservation 104 91 106

Russell-Smith J. , Edwards A. C. , Woinarski J. C. Z. , McCartney J. , Kerin S. , Winderlich S. , Murphy B. P. , and Watt F. (2009). The first ten years of the ‘Three Parks’ (Kakadu, Litchfield, Nitmiluk) fire regime and biodiversity monitoring program. In ‘Culture, Ecology and Economy of Fire Management in Northern Australia: Rekindling the Wurrk Tradition’. (Eds J. Russell-Smith, P. J. Whitehead and P. Cooke.) pp. 257–285. (CSIRO Publishing: Melbourne.)

Short J. Calaby J. H. 2001 The status of Australian mammals in 1922 – collections and field notes of museum collector Charles Hoy. Australian Zoologist 31 533 562

Short J. Turner B. 1994 A test of the vegetation mosaic hypothesis: a hypothesis to explain the decline and extinction of Australian mammals. Conservation Biology 8 439 449

Skeat A. J. , East T. J. , and Corbett L. K. (1996). Impact of feral water buffalo. In ‘Landscape and Vegetation Ecology of the Kakadu Region, Northern Australia’. (Eds C. M. Finlayson and I. V. Oertzen.). pp. 155–177. (Kluwer Academic Publishers: Dordrecht, The Netherlands.)

Smith K. E. Carpenter S. M. 2006 Potential spread of introduced black rat (Rattus rattus) parasites to endemic deer mice (Peromyscus maniculatus) on the California Channel Islands. Diversity & Distributions 12 742 748 doi:10.1111/j.1472-4642.2006.00279.x

Southgate R. Palmer C. Adams M. Masters P. Triggs B. Woinarski J. 1996 Population and habitat characteristics of the golden bandicoot (Isoodon auratus) on Marchinbar Island, Northern Territory. Wildlife Research 23 647 664 doi:10.1071/WR9960647

Sweet S. S. (2007). Comparative spatial ecology of two small arboreal monitors in northern Australia. Mertensiella 16, 378–402.

Tolstoy L. (1877). ‘Anna Karenina.’ edn 2000. (Penguin: London.)

Watson M. , and Woinarski J. (2003). Vertebrate monitoring and re-sampling in Kakadu National Park, 2002. Report to Parks Australia. Tropical Savannas Cooperative Research Centre, Darwin, NT.

Woinarski J. C. Z. Milne D. J. Wanganeen G. 2001 Changes in mammal populations in relatively intact landscapes of Kakadu National Park, Northern Territory, Australia. Austral Ecology 26 360 370 doi:10.1046/j.1442-9993.2001.01121.x

Woinarski J. C. Z. Armstrong M. Price O. McCartney J. Griffiths T. Fisher A. 2004 a The terrestrial vertebrate fauna of Litchfield National Park, Northern Territory: monitoring over a 6-year period, and response to fire history. Wildlife Research 31 587 596 doi:10.1071/WR03077

Woinarski J. C. Z. Risler J. Kean L. 2004 b The response of vegetation and vertebrate fauna to 23 years of fire exclusion in a tropical Eucalyptus open forest, Northern Territory, Australia. Austral Ecology 29 156 176 doi:10.1111/j.1442-9993.2004.01333.x

Wyatt K. B. Campos P. F. Gilbert M. T. P. Kolokotronis S.-O. Hynes W. H. DeSalle R. Daszak P. MacPhee R. D. E. Greenwood A. D. 2008 Historic mammal extinction on Christmas Island (Indian Ocean) correlates with introduced infectious disease. PLoS ONE 3 11 e3602 doi:10.1371/journal.pone.0003602

Export Citation