Optimal control of native predators Julien Martin a,b,c, * , Allan F. O’Connell Jr. d , William L. Kendall b , Michael C. Runge b , Theodore R. Simons e , Arielle H. Waldstein e , Shiloh A. Schulte e , Sarah. J. Converse b , Graham W. Smith b , Timothy Pinion f , Michael Rikard g , Elise F. Zipkin b a Florida Cooperative Fish and Wildlife Research Unit, University of Florida, FL 32611, USA b USGS Patuxent Wildlife Research Center, 12100 Beech Forest Road, Laurel, MD 20708, USA c Florida Fish and Wildlife Conservation Commission, Florida Fish and Wildlife Research Institute, St. Petersburg, FL 33701, USA d USGS Patuxent Wildlife Research Center, Beltsville Lab, BARC 308E, 10300 Baltimore Ave., Beltsville, MD 20705, USA e USGS North Carolina Cooperative Fish and Wildlife Research Unit, Department of Biology, North Carolina State University, Raleigh, NC 27622, USA f National Park Service, 100 Alabama St. SW, Atlanta, GA 30303, USA g Cape Lookout National Seashore, 131 Charles Street, Harkers Island, NC 28531, USA article info Article history: Received 2 January 2010 Received in revised form 1 April 2010 Accepted 12 April 2010 Available online 10 May 2010 Keywords: Structured decision-making Threatened and endangered species Raccoons Oystercatchers Adaptive management abstract We apply decision theory in a structured decision-making framework to evaluate how control of raccoons (Procyon lotor), a native predator, can promote the conservation of a declining population of American Oystercatchers (Haematopus palliatus) on the Outer Banks of North Carolina. Our management objective was to maintain Oystercatcher productivity above a level deemed necessary for population recovery while minimizing raccoon removal. We evaluated several scenarios including no raccoon removal, and applied an adaptive optimization algorithm to account for parameter uncertainty. We show how adaptive optimization can be used to account for uncertainties about how raccoon control may affect Oyster- catcher productivity. Adaptive management can reduce this type of uncertainty and is particularly well suited for addressing controversial management issues such as native predator control. The case study also offers several insights that may be relevant to the optimal control of other native predators. First, we found that stage-specific removal policies (e.g., yearling versus adult raccoon removals) were most efficient if the reproductive values among stage classes were very different. Second, we found that the optimal control of raccoons would result in higher Oystercatcher productivity than the minimum levels recommended for this species. Third, we found that removing more raccoons initially minimized the total number of removals necessary to meet long term management objectives. Finally, if for logistical reasons managers cannot sustain a removal program by removing a minimum number of raccoons annually, managers may run the risk of creating an ecological trap for Oystercatchers. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction High predation rates can be a serious problem for many pro- tected species and managers may seek to eradicate or control pre- dators that threaten protected prey populations (Courchamp et al., 2003; Meckstroth and Miles, 2005; Baxter et al., 2008). However, predator removal programs can be controversial and have demon- strated only mixed success (Côté and Sutherland, 1997). They have been criticized as ineffective, costly, requiring unsustainable effort, lacking specificity for the target predator, and increasingly, are viewed negatively by the public (Goodrich and Buskirk, 1995). Unfortunately, many predator removal programs have used an ad hoc approach when removing individuals, with little prior knowledge or consideration of impacts on either the predators themselves, the target prey, or the scope of the unintended conse- quences to other species in the system. Although alien predators are considered more dangerous than native predators in the decline and extinction of prey species (Salo et al., 2007), the impact of native predators on prey can also be sig- nificant under certain conditions (e.g., meso-predator release, sub- sidized predators [Crooks and Soulé, 1999; Gommper and Vanak, 2008]). Indeed, anthropogenic influences can result in an increase in food availability and cover, thereby increasing predator carrying capacity. Also, the effects of predation can be magnified if the abun- dance of prey species is reduced due to overharvest, pollution, com- petition from introduced species, or habitat loss or fragmentation. 0006-3207/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2010.04.023 * Corresponding author. Address: 100 8th Ave. SE, St. Petersburg, FL 33701, USA. Tel.: +1 727 896 8636; fax: +1 727 83 9176. E-mail addresses: julienm@ufl.edu (J. Martin), oconnell@usgs.gov (A.F. O’Con- nell), wkendall@usgs.gov (W.L. Kendall), mrunge@usgs.gov (M.C. Runge), tsimons@ ncsu.edu (T.R. Simons), ahwaldst@ncsu.edu (A.H. Waldstein), shiloh.schulte@ gmail.com (S.A. Schulte), sconverse@usgs.gov (Sarah. J. Converse), gwsmith@usgs. gov (G.W. Smith), timothy_pinion@nps.gov (T. Pinion), mrikard@nps.gov (M. Rikard), ezipkin@usgs.gov (E.F. Zipkin). Biological Conservation 143 (2010) 1751–1758 Contents lists available at ScienceDirect Biological Conservation journal homepage: www.elsevier.com/locate/biocon