307 Parkes et al.: Eradication of feral cats from large islands Eradication of feral cats from large islands: an assessment of the effort required for success John Parkes 1* , Penny Fisher 2 , Sue Robinson 3 and Alfonso Aguirre-Muñoz 4 1 Kurahaupo Consulting, 2 Ashdale Lane, Christchurch 8052, New Zealand 2 Landcare Research, PO Box 69040, Lincoln 7640, New Zealand 3 Invasive Species Branch, Department of Primary Industries, Parks, Water and Environment, 134 Macquarie St, Hobart, Tasmania, Australia 4 Grupo de Ecología y Conservación de Islas, A.C., Ensenada, Baja California, México *Author for correspondence (Email: john.parkes1080@gmail.com) Published online: 9 April 2014 Abstract: Feral cats (Felis catus) are predators and competitors of native species on many islands and are therefore the target of control efforts. Cat eradication has been achieved on 83 islands worldwide. Six of these successes have been from large islands (over 2000 ha) and have reported suffcient data to examine how the eradication was achieved through combinations of aerial and ground-based poison baiting, fumigation in rabbit burrows used by cats, cage and leghold trapping, day and night shooting, and hunting with dogs. No common sequence of tactics was deployed although leghold traps were used in the latter phases of most projects. It took a mean reported effort of 543 ± 341 person-days per 1000 ha of island over 5.2 ± 1.6 years to completely remove cats and validate success from the six islands. These precedents may assist in planning future proposals to eradicate cats from other large islands. Keywords: control effort; control sequence; Felis catus Introduction Predation by introduced cats (Felis catus) affects many native species (Dickman 1996; Gillies & Fitzgerald 2005; Loss et al. 2013) and particularly on islands where cat predation has led to extinctions of native species (Duffy & Capece 2012). Trophic interactions between feral cats, introduced primary prey (e.g. rodents or and rabbits), and native secondary prey (Sinclair et al. 1998) are at the core of debate over the order in which suites of invasive species should be eradicated (Glen et al. 2013) and the potential consequences of getting this wrong (e.g. Bergstrom et al. 2009 cf. Dowding et al. 2009). Efforts to mitigate cat impacts have led to sustained control efforts against cats on continents and very large islands (Reardon et al. 2012), removal from fenced exclosures (Young et al. 2013), and eradication from islands (Nogales et al. 2004; Campbell et al. 2011). This paper provides an assessment of the feasibility, methods and effort required to eradicate feral cats from large islands. To do this we reviewed cat eradications from six islands of over 2000 ha where suffcient data were reported to know how this was achieved and with what effort. Worldwide there are several proposals to eradicate feral cats from even larger islands (e.g. Aguirre-Muñoz et al. 2011; Campbell et al. 2011; Parkes et al. 2012, unpubl.; Bell & Bramley 2013; Glen et al. 2013; Nogales et al. 2013), and our review indicates what it might take to achieve future success, until at least the effciency of control methods and their application are improved (e.g. Johnston et al. 2011). Selecting case studies: background to the analysis Of 83 islands from which cats have been eradicated (see the lists in Nogales et al. (2004) updated by Campbell et al. (2011)) 11 were larger than 2000 ha, which we use to defne ‘large’ for this review. However, reports from only six of these larger islands (Table 1) contained enough detailed information to allow analysis of the sequence of control events used and the effort expended. Table 1. Islands from which feral cats have been eradicated and that met our case study criteria – over 2000 ha and where data on the project were available. __________________________________________________________________________________________________________________________________________________________________ Island Size (ha) Country Primary exotic prey species for cats Reference __________________________________________________________________________________________________________________________________________________________________ Marion 29 000 South Africa Mice Bester et al. (2002) Macquarie 12 780 Australia Rabbits, mice, ship rats Copson & Whinam (2001); Robinson & Copson (2014) Ascension 9700 UK Rabbits, mice, ship rats Ratcliffe et al. (2010) San Nicolas 5896 USA Nil Hanson et al. (2010) Little Barrier 2817 New Zealand Polynesian rats Veitch (2001) Baltra 2620 Ecuador Mice, ship rats Phillips et al. (2005) __________________________________________________________________________________________________________________________________________________________________ New Zealand Journal of Ecology (2014) 38(2): 307-314 © New Zealand Ecological Society. Available on-line at: http://www.newzealandecology.org/nzje/