A population viability analysis for the Island Fox on Santa Catalina Island,California |
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| Institution: | 1. Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, Ebertstrasse 1, D-07743 Jena, Germany;2. Department of Life Sciences, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy;1. Dipartimento di Scienze della Terra, Perugia University, Piazza Università, 06123 Perugia, Italy;2. Dipartimento di Scienze della Terra, Sapienza University of Rome, Piazzale A. Moro 5, 00185 Rome, Italy;3. Dipartimento di Scienze della Terra, Florence University, Via G. La Pira 4, 50121 Florence, Italy;1. Department of Cardiology, First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, China;2. Attardi Institute of Mitochondrial Biomedicine, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang 325035, China;3. Department of Cardiology, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, China;1. Key Laboratory of Bio-resources and Eco-environment (Ministry of Education), College of Life Sciences, Sichuan University, Chengdu 610064, PR China;2. Sichuan Laojunshan Natural Reserve, Pingshan, Sichuan 645350, PR China;3. Sichuan Key Laboratory of Conservation Biology on Endangered Wildlife, College of Life Sciences, Sichuan University, Chengdu 610064, PR China;4. Sichuan Good-doctor Pharmaceutical Group, Chengdu 610064, PR China;1. Institute for Sustainable Development and International relations (IDDRI), 27 rue Saint-Guillaume, 75337 Paris Cedex 07, France;2. Currently Commonwealth Secretariat, Previously Institute for Advanced Sustainability Studies (IASS);3. International Union for the Conservation of Nature (IUCN);4. Globelaw |
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| Abstract: | The island fox (Urocyon littoralis) on Santa Catalina Island is among the most imperiled species on the Channel Islands due to a recent outbreak of canine distemper virus (CDV). The western subpopulation, which was not exposed to CDV, is a crucial element in the recovery of foxes by providing a source of animals for translocation and captive breeding. Using the program VORTEX, we developed a population viability analysis for the Santa Catalina Island fox to (1) address the likelihood of population persistence, (2) estimate the current susceptibility of the population to catastrophic events, and (3) evaluate the efficacy of current restoration strategies of releasing captive bred foxes and transplanting wild animals. Overall, we found the population to be susceptible to catastrophic events; a 50% increase in mortality every 20 years was sufficient to elevate the extinction risk above 5%. Current management activities entail the transplanting of 12 juvenile foxes annually, which may reduce the viability of the western subpopulation. A minimum population size of at least 150 foxes should be maintained in each subpopulation to reduce the risk of extinction due to demographic stochasticity. Releases of translocated and captive bred animals affect the speed of recovery on the eastern half of Catalina Island, but not the probability of extinction, which is near zero under current conditions. We conducted a sensitivity analysis for demographic parameters by incrementally varying survival, fecundity and density-dependence parameters, while holding all other parameters constant. Sensitivity analyses identified mortality and mean litter size as the most sensitive parameters, while the implementation of density-dependence and environmental variation of model parameters did not seem to affect population performance. We conclude that the population of island foxes on Santa Catalina is currently at a critically low population level, but recovery of the species appears possible. |
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