Evidence-based culling of a facultative predator: Efficacy and efficiency components Ana Sanz-Aguilar a, * , Alejandro Martı´nez-Abraı´n a , Giacomo Tavecchia a , EduardoMı´nguez b , Daniel Oro a a Institut Mediterrani d’Estudis Avanc ¸ats IMEDEA (CSIC-UIB), Miquel Marque ´s 21, 07190 Esporles, Mallorca, Spain b Parque Natural Serra Gelada y su entorno litoral. Paseo de la carretera 34, 03501 Benidorm, Alicante, Spain ARTICLE INFO Article history: Received 20 August 2008 Received in revised form 28 October 2008 Accepted 5 November 2008 Available online 12 December 2008 Keywords: Breeding success Conservation Evidence-based management Storm-petrel Survival Yellow-legged gull ABSTRACT Human activities have greatly modified predator–prey dynamics within seabird communi- ties by favouring a rapid increase in density of large predatory gulls. To counteract such a subsidized growth, conservation agencies perform massive random culling programs, which generally fail to restore the original predator–prey relationship. We used long-term individual-based information to evaluate the effects of a selective culling of a top seabird predator, the yellow-legged gull (Larus michahellis), on the predatory pressure, survival and reproductive success probabilities of a secondary prey, the vulnerable European storm-petrel (Hydrobates pelagicus). The selective removal of only 16 gulls in 3 years led to a reduction of ca. 65% in the number of petrels killed, and to a relative increase in their sur- vival and breeding success probabilities of 16% and 23%, respectively. Our results show that only a few specialised predators were responsible for the bulk of the impact on a secondary prey and that the removal of those specialised individuals was an effective and efficient way to improve prey demographic parameters. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Seabird communities are characterized by networks of mul- tiple interactions among species; many of these have been much altered in recent times by human induced changes in marine resources (Stenhouse and Montevecchi, 1999; Sole ´ and Montoya, 2001; Votier et al., 2004b). These alterations have modified predator–prey dynamics within seabird com- munities owing to the negative effects of fisheries on fish stocks and by the increase of alternative food supplies, such as urban tips and fishery discards, which subsidize predators (Votier et al., 2004b; Furness et al., 2007). Gulls are the classic example of species affected by these deep and rapid changes; over the last century their populations have in- creased substantially (Oro et al., 1995; Thibault et al., 1996; Duhem et al., 2008) up to the point that large gulls are cur- rently perceived as a pest by wildlife managers, for a large number of reasons, including their impact on smaller and threatened syntopic species (Feare, 1991; Vidal et al., 1998; Finney et al., 2003; though see Oro and Martı ´nez-Abraı ´n, 2007). As a consequence, many conservation agencies have set up culling programs to control gull populations, which typically consist of systematic removal of large numbers of eggs, chicks or breeding adults (e.g. Blokpoel and Spaans, 1991). These programs are generally conducted at the local population level assuming that all individuals equally con- tribute to, or are equally responsible for, the conservation problem identified. This assumption is rarely supported 0006-3207/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2008.11.004 * Corresponding author: Tel.: +34 971611756; fax: +34 971611761. E-mail addresses: ana.sanz@uib.es, ana.sanzaguilar@gmail.com (A. Sanz-Aguilar), a.abrain@uib.es (A.Martı´nez-Abraı´n), g.tavec- chia@uib.es (G. Tavecchia), minguez_edu@gva.es (E. Mı ´nguez), d.oro@uib.es (D. Oro). BIOLOGICAL CONSERVATION 142 (2009) 424 – 431 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/biocon