Enumerating a continental-scale threat: How many feral cats are in Australia?
Legge, S and Murphy, BP and McGregor, H and Woinarski, JCZ and Augusteyn, J and Ballard, G and Baseler, M and Buckmaster, T and Dickman, CR and Doherty, T and Edwards, G and Eyre, T and Fancourt, BA and Ferguson, D and Forsyth, DM and Geary, WL and Gentle, M and Gillespie, G and Greenwood, L and Hohnen, R and Hume, S and Johnson, CN and Maxwell, M and McDonald, PJ and Morris, K and Moseby, K and Newsome, T and Nimmo, D and Paltridge, R and Ramsey, D and Read, J and Rendall, A and Rich, M and Ritchie, E and Rowland, J and Short, J and Stokeld, D and Sutherland, DR and Wayne, AF and Woodford, L and Zewe, F, Enumerating a continental-scale threat: How many feral cats are in Australia?, Biological Conservation, 206 pp. 293-303. ISSN 0006-3207 (2017) [Refereed Article]
Feral cats (Felis catus) have devastated wildlife globally. In Australia, feral cats are implicated in most recent mammal extinctions and continue to threaten native species. Cat control is a high-profile priority for Australian policy, research and management. To develop the evidence-base to support this priority, we first review information on cat presence/absence on Australian islands and mainland cat-proof exclosures, finding that cats occur across >99.8% of Australia's land area. Next, we collate 91 site-based feral cat density estimates in Australia and examine the influence of environmental and geographic influences on density. We extrapolate from this analysis to estimate that the feral cat population in natural environments fluctuates between 1.4 million (95% confidence interval: 1.0-2.3 million) after continent-wide droughts, to 5.6 million (95% CI: 2.5-11 million) after extensive wet periods. We estimate another 0.7 million feral cats occur in Australia's highly modified environments (urban areas, rubbish dumps, intensive farms). Feral cat densities are higher on small islands than the mainland, but similar inside and outside conservation land. Mainland cats reach highest densities in arid/semi-arid areas after wet periods. Regional variation in cat densities corresponds closely with attrition rates for native mammal fauna. The overall population estimate for Australia's feral cats (in natural and highly modified environments), fluctuating between 2.1 and 6.3 million, is lower than previous estimates, and Australian feral cat densities are lower than reported for North America and Europe. Nevertheless, cats inflict severe impacts on Australian fauna, reflecting the sensitivity of Australia's native species to cats and reinforcing that policy, research and management to reduce their impacts is critical.
feral cat, density, introduced predator, island, pest management, invasive species