The intact and the imperilled: contrasting mammal population trajectories between two large adjacent islands
Georgina Neave![https://orcid.org/0000-0001-6173-0881](/media/client/orcid_16x16.png)
![https://orcid.org/0000-0002-8230-3069](/media/client/orcid_16x16.png)
![https://orcid.org/0000-0002-8473-4540](/media/client/orcid_16x16.png)
A
B
Abstract
Native mammals continue to suffer widespread and severe declines across northern Australia’s tropical savannas. There is an increasing body of evidence that the primary driver of these declines is predation by feral cats (Felis catus) and that this is exacerbated by high-severity disturbance regimes (frequent high-intensity fires, and grazing and trampling by exotic megaherbivores) that simplify habitat, thereby increasing hunting efficiency. The large islands off the northern Australian coast – where some threats are either reduced or absent – provide a means of testing the conceptual model’s predictions.
To compare the trajectory and distribution of native mammal populations on two large, adjacent islands with markedly different disturbance regimes.
In 2020 and 2021, we resurveyed 111 historical sites across the two largest of the Tiwi Islands, Bathurst Island (42 sites) and Melville Island (69 sites) that were previously surveyed between 2000 and 2002. The Melville Island sites had also been resurveyed in 2015. We used the same live trapping method used in 2000–2002, supplemented with camera trapping.
On Bathurst Island, feral cats are rare, and we found no significant decrease in native mammal trap success or species richness, and the threatened brush-tailed rabbit-rat (Conilurus penicillatus melibius) appears stable. Conversely, cats occurred at relatively high abundance on Melville Island, and there was a 52% decline in trap success, a 47% reduction in species richness, and a 93% decline in trap success for the brush-tailed rabbit-rat over the 20-year period. The highest decreases in native mammal abundance and richness were in areas that were frequently burnt and had higher activity of feral cats. In contrast, in the absence of cats on Bathurst Island, native mammal abundance increased in frequently burnt areas.
While Bathurst Island remains one of Australia’s most important refuges for native mammals, neighbouring Melville Island is experiencing severe and ongoing mammal decline. We contend that this pattern primarily reflects the high abundance of cats on Melville Island compared to Bathurst Island.
Native mammal decline in northern Australian savannas is associated with abundant feral cats, but the relative contribution of disturbances in driving cat abundance remains less clear. An improved understanding of the constraints to feral cat populations in tropical savannas could enhance conservation management.
Keywords: Conilurus penicillatus, disturbance regimes, feral cats, feral herbivores, fire, native mammal declines, Tiwi Islands, tropical savannas.
References
Abbott I (2008) The spread of the cat, Felis catus, in Australia: re-examination of the current conceptual model with additional information. Conservation Science Western Australia 7, 1-17.
| Google Scholar |
Alzate A, Etienne RS, Bonte D (2019) Experimental island biogeography demonstrates the importance of island size and dispersal for the adaptation to novel habitats. Global Ecology and Biogeography 28, 238-247.
| Crossref | Google Scholar |
Andersen AN, Woinarski JCZ, Parr CL (2012) Savanna burning for biodiversity: fire management for faunal conservation in Australian tropical savannas: savanna burning for faunal diversity. Austral Ecology 37, 658-667.
| Crossref | Google Scholar |
Bayliss P, Bayliss P, Yeomans KM, Yeomans KM (1989) Distribution and abundance of feral livestock in the ‘Top End’ of the Northern Territory (1985-86), and their relation to population control. Wildlife Research 16, 651-676.
| Crossref | Google Scholar |
Beery S, Morris D, Yang S (2019) Efficient pipeline for camera trap image review. Available at http://arxiv.org/abs/1907.06772 [Accessed 4 December 2022]
Brook LA, Kutt AS (2011) The diet of the dingo (Canis lupus dingo) in north-eastern Australia with comments on its conservation implications. The Rangeland Journal 33, 79-85.
| Crossref | Google Scholar |
Burbidge AA, McKenzie NL (1989) Patterns in the modern decline of western Australia’s vertebrate fauna: causes and conservation implications. Biological Conservation 50, 143-198.
| Crossref | Google Scholar |
Campbell BL, Gallagher RV, Ens EJ (2022) Expanding the biocultural benefits of species distribution modelling with Indigenous collaborators: case study from northern Australia. Biological Conservation 274, 109656.
| Crossref | Google Scholar |
Darwin Centre for Bushfire Research (2023) North Australia and Rangelands Fire Information. Available at http://www.firenorth.org.au/nafi3/ [Verified 18 July 2024]
Davies HF, McCarthy MA, Firth RSC, Woinarski JCZ, Gillespie GR, Andersen AN, Geyle HM, Nicholson E, Murphy BP (2017) Top-down control of species distributions: feral cats driving the regional extinction of a threatened rodent in northern Australia. Diversity and Distributions 23, 272-283.
| Crossref | Google Scholar |
Davies HF, McCarthy MA, Firth RSC, Woinarski JCZ, Gillespie GR, Andersen AN, Rioli W, Puruntatameri J, Roberts W, Kerinaiua C, Kerinauia V, Womatakimi KB, Murphy BP (2018a) Declining populations in one of the last refuges for threatened mammal species in northern Australia. Austral Ecology 43, 602-612.
| Crossref | Google Scholar |
Davies HF, McCarthy MA, Rioli W, Puruntatameri J, Roberts W, Kerinaiua C, Kerinauia V, Womatakimi KB, Andersen AN, Murphy BP (2018b) An experimental test of whether pyrodiversity promotes mammal diversity in a northern Australian savanna. Journal of Applied Ecology 55, 2124-2134.
| Crossref | Google Scholar |
Davies HF, Maier SW, Murphy BP (2020) Feral cats are more abundant under severe disturbance regimes in an Australian tropical savanna. Wildlife Research 47, 624-632.
| Crossref | Google Scholar |
Davies HF, Rangers TL, Rees MW, Stokeld D, Miller AC, Gillespie GR, Murphy BP (2022a) Variation in feral cat density between two large adjacent islands in Australia’s monsoon tropics. Pacific Conservation Biology 28, 18-24.
| Crossref | Google Scholar |
Davies HF, Rangers TL, Nicholson E, Murphy BP (2022b) Northern brown bandicoot (Isoodon macrourus) and common brushtail possum (Trichosurus vulpecula) density on the Tiwi Islands: insights and implications. Pacific Conservation Biology 28, 224-230.
| Crossref | Google Scholar |
DeMars CA, Boutin S (2018) Nowhere to hide: effects of linear features on predator–prey dynamics in a large mammal system. Journal of Animal Ecology 87, 274-284.
| Crossref | Google Scholar | PubMed |
Dickie M, Serrouya R, McNay RS, Boutin S (2017) Faster and farther: wolf movement on linear features and implications for hunting behaviour. Journal of Applied Ecology 54, 253-263.
| Crossref | Google Scholar |
Dickie M, Serrouya R, Avgar T, McLoughlin P, McNay RS, DeMars C, Boutin S, Ford AT (2022) Resource exploitation efficiency collapses the home range of an apex predator. Ecology 103, e3642.
| Crossref | Google Scholar |
Dickman CR (1996) Impact of exotic generalist predators on the native fauna of Australia. Wildlife Biology 2, 185-195.
| Crossref | Google Scholar |
Doherty TS, Davis RA, van Etten EJB, Algar D, Collier N, Dickman CR, Edwards G, Masters P, Palmer R, Robinson S (2015) A continental-scale analysis of feral cat diet in Australia. Journal of Biogeography 42, 964-975.
| Crossref | Google Scholar |
Doherty TS, Davis NE, Dickman CR, Forsyth DM, Letnic M, Nimmo DG, Palmer R, Ritchie EG, Benshemesh J, Edwards G, Lawrence J, Lumsden L, Pascoe C, Sharp A, Stokeld D, Myers C, Story G, Story P, Triggs B, Venosta M, Wysong M, Newsome TM (2019) Continental patterns in the diet of a top predator: Australia’s dingo. Mammal Review 49, 31-44.
| Crossref | Google Scholar |
Doody JS, Green B, Rhind D, Castellano CM, Sims R, Robinson T (2009) Population-level declines in Australian predators caused by an invasive species. Animal Conservation 12, 46-53.
| Crossref | Google Scholar |
Fernández-Palacios JM, Kreft H, Irl SDH, Norder S, Ah-Peng C, Borges PAV, Burns KC, de Nascimento L, Meyer J-Y, Montes E, Drake DR (2021) Scientists’ warning – the outstanding biodiversity of islands is in peril. Global Ecology and Conservation 31, e01847.
| Crossref | Google Scholar | PubMed |
Fillios MA, Taçon PSC (2016) Who let the dogs in? A review of the recent genetic evidence for the introduction of the dingo to Australia and implications for the movement of people. Journal of Archaeological Science: Reports 7, 782-792.
| Crossref | Google Scholar |
Firth RSC, Woinarski JCZ, Brennan KG, Hempel C (2006) 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.
| Crossref | Google Scholar |
Firth RSC, Brook BW, Woinarski JCZ, Fordham DA (2010) Decline and likely extinction of a northern Australian native rodent, the Brush-tailed Rabbit-rat Conilurus penicillatus. Biological Conservation 143, 1193-1201.
| Crossref | Google Scholar |
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 (2014) The current decline of tropical marsupials in Australia: is history repeating? Global Ecology and Biogeography 23, 181-190.
| Crossref | Google Scholar |
Frank ASK, Johnson CN, Potts JM, Fisher A, Lawes MJ, Woinarski JCZ, Tuft K, Radford IJ, Gordon IJ, Collis M-A, Legge S (2014) Experimental evidence that feral cats cause local extirpation of small mammals in Australia’s tropical savannas. Journal of Applied Ecology 51, 1486-1493.
| Crossref | Google Scholar |
Geyle HM, Woinarski JCZ, Baker GB, Dickman CR, Dutson G, Fisher DO, Ford H, Holdsworth M, Jones ME, Kutt A, Legge S, Leiper I, Loyn R, Murphy BP, Menkhorst P, Reside AE, Ritchie EG, Roberts FE, Tingley R, Garnett ST (2018) Quantifying extinction risk and forecasting the number of impending Australian bird and mammal extinctions. Pacific Conservation Biology 24, 157.
| Crossref | Google Scholar |
Geyle HM, Guillera-Arroita G, Davies HF, Firth RSC, Murphy BP, Nimmo DG, Ritchie EG, Woinarski JCZ, Nicholson E (2019) Towards meaningful monitoring: a case study of a threatened rodent. Austral Ecology 44, 223-236.
| Crossref | Google Scholar |
Greenberg S (2020) Timelapse: an image analyser for camera traps (version 2.2.3.6). Available at https://www.saul.cpsc.ucalgary.ca/timelapse/ [Accessed 10 April 2022]
Griffiths AD, Garnett ST, Brook BW (2015) Fire frequency matters more than fire size: testing the pyrodiversity–biodiversity paradigm for at-risk small mammals in an Australian tropical savanna. Biological Conservation 186, 337-346.
| Crossref | Google Scholar |
Heiniger J, Gillespie G (2018) High variation in camera trap-model sensitivity for surveying mammal species in northern Australia. Wildlife Research 45, 578-585.
| Crossref | Google Scholar |
Heiniger J, Davies HF, Gillespie GR (2020) Status of mammals on Groote Eylandt: safe haven or slow burn? Austral Ecology 45, 759-772.
| Crossref | Google Scholar |
Hradsky BA (2020) Conserving Australia’s threatened native mammals in predator-invaded, fire-prone landscapes. Wildlife Research 47, 1-15.
| Crossref | Google Scholar |
Kutt AS (2012) Feral cat (Felis catus) prey size and selectivity in north-eastern Australia: implications for mammal conservation: feral cat prey size and selection. Journal of Zoology 287, 292-300.
| Crossref | Google Scholar |
Kutt AS, Woinarski JCZ (2007) The effects of grazing and fire on vegetation and the vertebrate assemblage in a tropical savanna woodland in north-eastern Australia. Journal of Tropical Ecology 23, 95-106.
| Crossref | Google Scholar |
Lawes MJ, Murphy BP, Fisher A, Woinarski JCZ, Edwards AC, Russell-Smith J (2015) Small mammals decline with increasing fire extent in northern Australia: evidence from long-term monitoring in Kakadu National Park. International Journal of Wildland Fire 24, 712-722.
| Crossref | Google Scholar |
Leahy L, Legge SM, Tuft K, McGregor HW, Barmuta LA, Jones ME, Johnson CN (2015) Amplified predation after fire suppresses rodent populations in Australia’s tropical savannas. Wildlife Research 42, 705-716.
| Crossref | Google Scholar |
Legge S, Kennedy MS, Lloyd R, Murphy SA, Fisher A (2011) Rapid recovery of mammal fauna in the central Kimberley, northern Australia, following the removal of introduced herbivores: recovery of tropical savanna mammals. Austral Ecology 36, 791-799.
| Crossref | Google Scholar |
Legge S, Smith JG, James A, Tuft KD, Webb T, Woinarski JCZ (2019) Interactions among threats affect conservation management outcomes: livestock grazing removes the benefits of fire management for small mammals in Australian tropical savannas. Conservation Science and Practice 1, e52.
| Crossref | Google Scholar |
McGregor HW, Legge S, Jones ME, Johnson CN (2014) Landscape management of fire and grazing regimes alters the fine-scale habitat utilisation by feral cats. PLoS ONE 9, e109097.
| Crossref | Google Scholar | PubMed |
McGregor H, Legge S, Jones ME, Johnson CN (2015) Feral cats are better killers in open habitats, revealed by animal-borne video. PLoS ONE 10, e0133915.
| Crossref | Google Scholar | PubMed |
Murphy BP, Davies HF (2014) There is a critical weight range for Australia’s declining tropical mammals: critical weight range for Australia’s declining tropical mammals. Global Ecology and Biogeography 23, 1058-1061.
| Crossref | Google Scholar |
Murphy BP, Woolley L-A, Geyle HM, Legge SM, Palmer R, Dickman CR, Augusteyn J, Brown SC, Comer S, Doherty TS, Eager C, Edwards G, Fordham DA, Harley D, McDonald PJ, McGregor H, Moseby KE, Myers C, Read J, Riley J, Stokeld D, Trewella GJ, Turpin JM, Woinarski JCZ (2019) Introduced cats (Felis catus) eating a continental fauna: the number of mammals killed in Australia. Biological Conservation 237, 28-40.
| Crossref | Google Scholar |
O’Brien TG, Kinnaird MF, Wibisono HT (2003) Crouching tigers, hidden prey: Sumatran tiger and prey populations in a tropical forest landscape. Animal Conservation 6, 131-139.
| Crossref | Google Scholar |
Orr DM, O’Reagain PJ (2011) Managing for rainfall variability: impacts of grazing strategies on perennial grass dynamics in a dry tropical savanna. The Rangeland Journal 33, 209-220.
| Crossref | Google Scholar |
Pardon LG, Brook BW, Griffiths AD, Braithwaite RW (2003) Determinants of survival for the northern brown bandicoot under a landscape-scale fire experiment. Journal of Animal Ecology 72, 106-115.
| Crossref | Google Scholar |
Penton CE, Davies HF, Radford IJ, Woolley L-A, Rangers TL, Murphy BP (2021) A hollow argument: understory vegetation and disturbance determine abundance of hollow-dependent mammals in an Australian tropical savanna. Frontiers in Ecology and Evolution 9, 739550.
| Crossref | Google Scholar |
Potter LC, Brady CJ, Murphy BP (2019) Accuracy of identifications of mammal species from camera trap images: a northern Australian case study. Austral Ecology 44, 473-483.
| Crossref | Google Scholar |
Radford IJ, Gibson LA, Corey B, Carnes K, Fairman R (2015) Influence of fire mosaics, habitat characteristics and cattle disturbance on mammals in fire-prone savanna landscapes of the northern Kimberley. PLoS ONE 10, e0130721.
| Crossref | Google Scholar | PubMed |
Radford IJ, Corey B, Carnes K, Shedley E, McCaw L, Woolley L-A (2021) Landscape-scale effects of fire, cats, and feral livestock on threatened savanna mammals: unburnt habitat matters more than pyrodiversity. Frontiers in Ecology and Evolution 9, 739817.
| Crossref | Google Scholar |
R Core Team (2023) ‘R: a language and environment for statistical computing. R version 4.3.1.’ (R Foundation for Statistical Computing: Vienna, Austria) Available at https://www.R-project.org/
Russell-Smith J, Whitehead PJ, Cook GD, Hoare JL (2003) Response of eucalyptus-dominated savanna to frequent fires: lessons from Munmarlary, 1973–1996. Ecological Monographs 73, 349-375.
| Crossref | Google Scholar |
Shine R (2010) The ecological impact of invasive cane toads (Bufo marinus) in Australia. The Quarterly Review of Biology 85, 253-291.
| Crossref | Google Scholar | PubMed |
Start AN, Burbidge AA, McKenzie NL, Palmer C (2007) The status of mammals in the North Kimberley, Western Australia. Australian Mammalogy 29, 1-16.
| Crossref | Google Scholar |
Stobo-Wilson A (2018) Ecology of the savanna glider (Petaurus ariel) in tropical northern Australia. PhD Thesis, Charles Darwin University, Darwin. doi:10.25913/5EA9028A3A782
Stobo-Wilson AM, Murphy BP, Cremona T, Carthew SM (2019) Contrasting patterns of decline in two arboreal marsupials from Northern Australia. Biodiversity and Conservation 28, 2951-2965.
| Crossref | Google Scholar |
Stobo-Wilson AM, Stokeld D, Einoder LD, Davies HF, Fisher A, Hill BM, Mahney T, Murphy BP, Scroggie MP, Stevens A, Woinarski JCZ, Bawinanga Rangers, Warddeken Rangers, Gillespie GR (2020a) Bottom-up and top-down processes influence contemporary patterns of mammal species richness in Australia’s monsoonal tropics. Biological Conservation 247, 108638.
| Crossref | Google Scholar |
Stobo-Wilson AM, Stokeld D, Einoder LD, Davies HF, Fisher A, Hill BM, Mahney T, Murphy BP, Stevens A, Woinarski JCZ, Rangers B, Warddeken Rangers, Gillespie GR (2020b) Habitat structural complexity explains patterns of feral cat and dingo occurrence in monsoonal Australia. Diversity and Distributions 26, 832-842.
| Crossref | Google Scholar |
Stobo-Wilson AM, Murphy BP, Legge SM, Caceres-Escobar H, Chapple DG, Crawford HM, Dawson SJ, Dickman CR, Doherty TS, Fleming PA, Garnett ST, Gentle M, Newsome TM, Palmer R, Rees MW, Ritchie EG, Speed J, Stuart J-M, Suarez-Castro AF, Thompson E, Tulloch A, Turpin JM, Woinarski JCZ (2022) Counting the bodies: estimating the numbers and spatial variation of Australian reptiles, birds and mammals killed by two invasive mesopredators. Diversity and Distributions 28, 976-991.
| Crossref | Google Scholar |
Stokeld D, Fisher A, Gentles T, Hill B, Triggs B, Woinarski JCZ, Gillespie GR (2018) What do predator diets tell us about mammal declines in Kakadu National Park? Wildlife Research 45, 92-101.
| Crossref | Google Scholar |
Vigilante T, Bowman DMJS (2004) Effects of fire history on the structure and floristic composition of woody vegetation around Kalumburu, North Kimberley, Australia: a landscape-scale natural experiment. Australian Journal of Botany 52, 381-404.
| Crossref | Google Scholar |
von Takach B, Scheele BC, Moore H, Murphy BP, Banks SC (2020) Patterns of niche contraction identify vital refuge areas for declining mammals. Diversity and Distributions 26, 1467-1482.
| Crossref | Google Scholar |
Woinarski JCZ, Milne DJ, Wanganeen G (2001) Changes in mammal populations in relatively intact landscapes of Kakadu National Park, Northern Territory, Australia. Austral Ecology 26, 360-370.
| Crossref | Google Scholar |
Woinarski J, Oakwood M, Winter J, Burnett S, Milne D, Foster P, Myles H, Holmes B (2008) Surviving the toads: patterns of persistence of the northern quoll Dasyurus hallucatus in Queensland. Report to the Australian Government’s natural Heritage Trust, Canberra. doi:10.13140/RG.2.2.24203.41767
Woinarski JCZ, Armstrong M, Brennan K, Fisher A, Griffiths AD, Hill B, Milne DJ, Palmer C, Ward S, Watson M, Winderlich S, Young S (2010) Monitoring indicates rapid and severe decline of native small mammals in Kakadu National Park, northern Australia. Wildlife Research 37, 116-126.
| Crossref | Google Scholar |
Woinarski JCZ, Legge S, Fitzsimons JA, Traill BJ, Burbidge AA, Fisher A, Firth RSC, Gordon IJ, Griffiths AD, Johnson CN, McKenzie NL, Palmer C, Radford I, Rankmore B, Ritchie EG, Ward S, Ziembicki M (2011a) The disappearing mammal fauna of northern Australia: context, cause, and response. Conservation Letters 4, 192-201.
| Crossref | Google Scholar |
Woinarski JCZ, Ward S, Mahney T, Bradley J, Brennan K, Ziembicki M, Fisher A (2011b) The mammal fauna of the Sir Edward Pellew island group, Northern Territory, Australia: refuge and death-trap. Wildlife Research 38, 307-322.
| Crossref | Google Scholar |
Woinarski J, Burbidge A, Harrison P (2014) ‘Action plan for Australian mammals 2012.’ (CSIRO Publishing: Melbourne, Vic, Australia) doi:10.1071/9780643108745
Woinarski JCZ, Burbidge AA, Harrison PL (2015) Ongoing unraveling of a continental fauna: decline and extinction of Australian mammals since European settlement. Proceedings of the National Academy of Sciences 112, 4531-4540.
| Crossref | Google Scholar |
Woolley L-A, Geyle HM, Murphy BP, Legge SM, Palmer R, Dickman CR, Augusteyn J, Comer S, Doherty TS, Eager C, Edwards G, Harley DKP, Leiper I, McDonald PJ, McGregor HW, Moseby KE, Myers C, Read JL, Riley J, Stokeld D, Turpin JM, Woinarski JCZ (2019) Introduced cats Felis catus eating a continental fauna: inventory and traits of Australian mammal species killed. Mammal Review 49, 354-368.
| Crossref | Google Scholar |
Ziembicki MR, Woinarski JCZ, Mackey B (2013) Evaluating the status of species using Indigenous knowledge: novel evidence for major native mammal declines in northern Australia. Biological Conservation 157, 78-92.
| Crossref | Google Scholar |
Ziembicki MR, Woinarski JCZ, Webb JK, Vanderduys E, Tuft K, Smith J, Ritchie EG, Reardon TB, Radford IJ, Preece N, Perry J, Murphy BP, McGregor H, Legge S, Leahy L, Lawes MJ, Kanowski J, Johnson CN, James A, Griffiths AD, Gillespie G, Frank ASK, Fisher A, Burbidge AA (2015) Stemming the tide: progress towards resolving the causes of decline and implementing management responses for the disappearing mammal fauna of northern Australia. Therya 6, 169-226.
| Crossref | Google Scholar |