Foraging effort in Magellanic penguins: balancing the energy books for survival?
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The determination of activity-specific energy expenditure of wild animals is key in ecology and conservation sciences. Energy management is crucial for seabirds during the breeding season when they need to maintain a positive balance between energy intake and the metabolic costs for them and their young. We analysed information from accelerometers to estimate the energy expenditure of Magellanic penguins (Spheniscus magellanicus) foraging at sea during the early chick-rearing period from four Patagonian colonies (i.e. Punta Norte, Bahía Bustamante, Puerto Deseado and Puerto San Julián). We studied how activity-specific energy consumption affected total energy expenditure during foraging and considered how this related to the current status and trends of breeding populations. The derived diving energy expenditure of penguins differed between sites, with inter-colony differences being primarily due to variability during the bottom and ascent phases of the dives: bottom phase energy expenditure was largely determined by the total distances travelled during the search, pursuit, and capture of prey, rather than the time per se allocated to this phase. Those colonies where the rate of population change was lowest also expended the most energy per trip due to greater times spent underwater and/or undertaking a higher number of dives per trip. Finally, the total energy consumption as well as the rate of energy expenditure per trip was good indicators of trends in breeding populations.
KeywordsTotal Energy Expenditure Daily Diary Bottom Phase Metabolic Power Estimate Energy Expenditure
Research was funded by grants from the Wildlife Conservation Society (WCS), Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina (CONICET), and Agencia Nacional de Promoción Científica y Tecnológica to FQ and by a Rolex Award for Enterprise awarded to RPW. We want to thank the POGO (Partnership for Observation of the Global Oceans, http://www.ocean-partners.org/) for the award to Juan Emilio Sala to enable him to conduct a training period at Swansea University (2010). We want to especially thank A. Gómez-Laich for her invaluable assistance in statistical analysis using R. We also thank the respective Conservation Agencies from the provinces of Chubut and Santa Cruz for the permits to work in the different protected areas, and the Centro Nacional Patagónico (CENPAT-CONICET) for institutional and logistical support. J. E. Sala is supported by a postdoctoral fellowship from CONICET. Finally, we particularly thank those anonymous reviewers who provided valuable comments and contributed to a significant improvement of this paper and to Dr. Lorien Pichegru for her positive approach to refereeing and the abtterment of science.
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