Unexpected outcomes of invasive predator control: the importance of evaluating conservation management actions J. C. Walsh 1 *, K. A. Wilson 1 , J. Benshemesh 2 & H. P. Possingham 1 1 School of Biological Sciences, University of Queensland, Brisbane, Qld, Australia 2 Department of Zoology, La Trobe University, Bundoora, Vic, Australia Keywords conservation outcome; evidence-based conservation; fox baiting; malleefowl; management effectiveness; return on investment. Correspondence Jessica Walsh, School of Biological Sciences, University of Queensland, St Lucia, Qld 4072, Australia. Tel: +61 7 3365 2494; Fax: 61 7 3365 1655 Email jessica.walsh@uqconnect.edu.au Editor: Todd Katzner Associate Editor: Daniel Rondeau *Current address: Conservation Science Group, Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK. Received 12 April 2011; accepted 17 February 2012 doi:10.1111/j.1469-1795.2012.00537.x Abstract Decisions regarding the implementation of conservation management actions should be based on the effectiveness of past investments. However, because of limited evaluation of existing data, actions may be prescribed without evidence of producing a beneficial conservation outcome. We analysed empirical data, col- lected over 23 years across southern Australia, on the impact of fox baiting on malleefowl to determine its effectiveness. We employed data from extensive moni- toring surveys to evaluate the observed relationships between investment in fox control, fox baiting intensity, fox presence and two alternative measures of the malleefowl’s response: the number of breeding pairs and population growth. This study is the first to quantify the return on investment from fox control in a conservation context. We discovered there is limited quantitative evidence for a benefit of fox baiting on malleefowl, despite it being the main management action implemented for this nationally threatened, well-studied and iconic species. We found that fox baiting did not significantly decrease the presence of foxes and fox presence was positively correlated with malleefowl conservation. Malleefowl breeding population size increased with investment in baiting, although this rela- tionship depended on the number of years the site had been baited. Nonetheless, most sites had a negative relationship between investment and breeding popula- tion. In contrast, malleefowl population growth did not benefit from baiting, suggesting that fox baiting is generally not a cost-effective management action for the conservation of this species. This study provides a powerful example of why management decisions should be based on evidence, rather than ecological intui- tion. Even though the malleefowl is one of the best-monitored species of conser- vation concern in Australia, we are still uncertain how to cost-effectively manage this species. We emphasize the urgent need to assess what data we have and determine which species and what actions are most in need of evaluation. Introduction The continuing global decline of biodiversity (Butchart et al., 2010) necessitates active management of threatened species. Given that funding for conservation is limited (James, Gaston & Balmford, 2001; Balmford et al., 2003), it is essential to invest in effective and efficient management actions to ensure that conservation outcomes are maximized and limited resources are spent wisely (Wilson et al., 2007; Underwood et al., 2008). A key part of prioritizing investments is an understanding of how the target species or the environment will respond to a management action (Murdoch et al., 2007). The return on investment is the increase in benefit with investment divided by the cost of investment. This can be modelled using the relationship between the level of investment and the result- ing conservation outcome, i.e. the observed benefit. Such information can allow conservation managers to determine the marginal benefits obtained from investing in a manage- ment action. Using this investment–outcome relationship, we can then predict whether prescribed actions will be effec- tive at achieving the defined conservation objective, gauge whether the cost of implementing the actions falls within the budget allocated for the project, compare the cost- effectiveness of different management actions, and prioritize these actions to gain the greatest conservation outcome for a fixed budget or achieve a specified objective for the lowest cost; all of which are essential components in the conserva- tion resource allocation process (Mace, Possingham & Leader-Williams, 2006). Often, however, the relationship between the level of investment and the conservation outcome is unknown Animal Conservation. Print ISSN 1367-9430 Animal Conservation 15 (2012) 319–328 © 2012 The Authors. Animal Conservation © 2012 The Zoological Society of London 319