The eradication of feral cats from Ascension Island and its subsequent recolonization by seabirds N orman R atcliffe ,M ike B ell ,T ara P elembe ,D ave B oyle R aymond B enjamin R ichard W hite ,B rendan G odley J im S tevenson and S arah S anders Abstract The introduction of mammal predators to islands often results in rapid declines in the number and range of seabirds. On Ascension Island the introduction of cats in 1815 resulted in extirpation of large seabird colonies from the main island, with relict populations of most species persisting only in cat-inaccessible locations. We describe the eradication of feral cats from this large and populated island. The campaign had to minimize risk to humans and main- tain domestic animals in a state that prevented them re- establishing a feral population. Feral cat numbers declined rapidly in response to the strategic deployment of poisoning and live trapping, and cats were eradicated from the island within 2 years. During the project 38% of domestic cats were killed accidentally, which caused public consternation; we make recommendations for reducing such problems in future eradications. Since the completion of the eradication campaign cat predation of adult seabirds has ceased and five seabird species have recolonized the mainland in small but increasing numbers. Breeding success of seabirds at Ascen- sion was low compared to that of conspecifics elsewhere, and the roles of food availability, inexperience of parent birds and black rat predation in causing this warrant further investi- gation. It is likely that the low breeding success will result in the rate of increase in seabird populations being slow. Keywords Ascension Island, cat eradication, invasive spe- cies, island restoration, recolonization, tropical seabirds This paper contains supplementary material that can be found online at http://journals.cambridge.org Introduction S eabirds have life histories characterized by longevity and low fecundity (Weimerskirch, 2002) and many species nest in colonies on the ground. These are traits that render them vulnerable to mammalian predation. Intro- duction of mammalian predators to oceanic islands hosting seabird colonies typically results in a rapid decline in numbers (Moors & Atkinson, 1984), with relict populations persisting only on cliff ledges or islets that are inaccessible to predators. Predation by invasive mammals has resulted in the probable global extinction of two seabird species (Guadalupe storm petrel Oceanodroma macrodactyla and Jamaica petrel Pterodroma caribbaea) and contributes to the globally threatened status of many others (BirdLife International, 2000). Among the mammalian predators widely introduced to islands by man, cats Felis silvestris catus are particularly damaging because they are capable of preying upon adults of all but the largest seabird species, as well as their chicks (Moors & Atkinson, 1984). Removing cats from affected islands can benefit seabirds by reducing mortality (Keitt & Tershy, 2003; Rodriguez et al., 2006; Peck et al., 2008), allowing recolonization of areas from which they were extirpated (Ha ¨nel & Chown, 1998; Wolf, 2002) and population recovery (Cooper et al., 1995). Cat eradication campaigns have been conducted on 75 islands using a variety of techniques (Donlan & Wilcox, 2008). Most islands have been small as these are logistically easier to treat (Nogales et al., 2004) but the treatment of larger islands is desirable because these have the capacity to host greater species diversity and larger populations com- pared to small islands (Rosenzweig, 1995). However, cam- paigns on large islands are complicated by the fact that they are more likely to have human habitation (Nogales et al., 2004; Genovesi, 2007), and the risk of primary or secondary poisoning of the human population has to be completely eliminated. Moreover, cats are popular as pets and eradication campaigns may face opposition from inhabitants wishing to keep and import domestic animals during and after eradica- tion and because of concerns for the suffering of feral animals. Methods that allow eradication campaigns to be conducted on inhabited islands, including public relations and field proto- cols, are therefore required (Nogales et al., 2004). Ascension Island is an infamous example of the adverse impacts of cats on seabird populations. Historical records NORMAN RATCLIFFE* (Corresponding author), RICHARD WHITE, JIM STEVENSON and SARAH SANDERS RSPB, The Lodge, Sandy, Bedfordshire, UK. E-mail notc@bas.ac.uk MIKE BELL and DAVE BOYLE Wildlife Management International Ltd, Blenheim, New Zealand. TARA PELEMBE and RAYMOND BENJAMIN Ascension Island Government Conservation Department, Georgetown, Ascension Island, South Atlantic. BRENDAN GODLEY Centre for Ecology and Conservation, University of Exeter, Cornwall Campus, Penryn, UK. *Current address: British Antarctic Survey, Natural Environmental Research Council, High Cross, Madingley Road, Cambridge, CB4 0ET, UK. Received 8 May 2009. Revision requested 23 July 2009. Accepted 26 August 2009. ª 2009 Fauna & Flora International, Oryx, 44(1), 20–29 doi:10.1017/S003060530999069X