Competitive Asymmetries in the Use of Supplementary Food by the Endangered Iberian Lynx (Lynx pardinus) Jose ´ V. Lo ´ pez-Bao*, Alejandro Rodrı´guez, Francisco Palomares Department of Conservation Biology, Estacio ´ n Biolo ´ gica de Don ˜ ana (CSIC), Seville, Spain Abstract Background: As a conservation tool, supplementary feeding programs may be directed to specific individuals or sectors of the target population whose productivity or survival is thought to be limited by food scarcity. However, the use of supplemental food by different sex and age classes has received little attention. We studied individual variation in the access of the endangered Iberian lynx (Lynx pardinus) to supplementary food. Methodology/Principal Findings: From 5349 pictures taken with automatic cameras placed in 25 feeding stations, we identified 28 individuals whose sex and age were known. All individuals known to live in areas subjected to supplementation regularly visited feeding stations. Food consumption was not proportional to expected variations in energy demand within sex and age classes. Food consumption by males was higher than by females, and increased with age, in agreement with a despotic distribution. Food consumption also increased with lynx body mass, and this pattern held for individuals sharing the same breeding territories. The access of inferior competitors increased with the number of feeding stations available within lynx territories. Conclusions/Significance: All lynx exposed to food supplementation made a regular use of extra food but individuals predicted to be competitively dominant visited stations more frequently than subordinates of the same breeding territory. Our results suggest that insufficient provision of supplementary food could restrict the access of juveniles, or even adult females, to feeding stations. Limited consumption by these target individuals may compromise the efficiency of the supplementary feeding programme at the population level, in endangered species that, as the Iberian lynx, exhibit marked sexual dimorphism in body size. Citation: Lo ´ pez-Bao JV, Rodrı ´guez A, Palomares F (2009) Competitive Asymmetries in the Use of Supplementary Food by the Endangered Iberian Lynx (Lynx pardinus). PLoS ONE 4(10): e7610. doi:10.1371/journal.pone.0007610 Editor: Michael Somers, University of Pretoria, South Africa Received April 15, 2009; Accepted October 2, 2009; Published October 28, 2009 Copyright: ß 2009 Lo ´ pez-Bao et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This research was funded by the projects CGL2004-00346/BOS (Spanish Ministry of Education and Science) and 17/2005 (Spanish Ministry of the Environment; National Parks Research Programme), and BP-Oil Spain. The Regional Government of Andalusia (CMA, Junta de Andalucı ´-a) partially funded the supplementary feeding programme under the European Union LIFE project LIFE-02NAT/8609. Land-Rover Espan ˜ a S.A. kindly lended two vehicles for this work. JVLB was supported by a FPU fellow (Ministry of Education). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: jvlb@ebd.csic.es Introduction Food supplementation experiments have long been used to explore whether predictors of fitness such as condition [1] and productivity [2], or population parameters such as survival [3] and recruitment [4], depend upon food availability. To a lesser extent, food supplementation has been employed for a number of applied purposes, including prevention of crop damage by wildlife [5], retention of translocated animals [6], or conservation of endangered populations [7,8]. In a conservation context, supple- mentation is often targeted at specific sectors of a target population (i.e. sex and age classes) during periods when food limitation is thought to be critical [9]. The endangered Iberian lynx (Lynx pardinus) feeds almost exclusively upon European rabbits (Oryctolagus cuniculus; [10]), and rabbit scarcity has been identified as a major factor of lynx decline [11]. Even in protected areas inhabited by lynx, most sites do not reach the threshold rabbit density that allows lynx reproduction [12,13] or settlement, which reduces the per capita productivity, extends the duration of natal dispersal, increases subadult mortality rates, and reduces recruitment [14,15]. This situation prompted a rabbit supplementation programme [16] whose major aims included improving reproductive rates of Iberian lynx within existing territories as well as creating new ones by promoting disperser settlement. By enhancing territory quality, supplementary food should increase body condition and produc- tivity of adult females, thus improving the reproductive output of the population. Food supplementation should also transform empty areas into potential territories, offering more opportunities for subadults to settle down, and to do it earlier, thus reducing dispersal time and associated high risk of mortality [14]. Since female settlement precedes male arrival and subsequent breeding, the supplementation programme implicitly identifies adult and juvenile females as target individuals. The overall biomass of supplemented rabbits taken by lynx has been estimated to be twice that required to satisfy the energy requirements of the population fraction exposed to this resource [16], according to a model of metabolic cost [17]. However, it is PLoS ONE | www.plosone.org 1 October 2009 | Volume 4 | Issue 10 | e7610