Seascapes of fear: evaluating sublethal predator effects experienced and generated by marine mammals |
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Authors: | Aaron J Wirsing Michael R Heithaus Alejandro Frid Lawrence M Dill |
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Institution: | Department of Biological Sciences, Florida International University, Biscayne Bay Campus, 3000 NE 151st Street, North Miami, Florida 33181, U.S.A. E-mail:; 352 Creek Road, Bowen Island, British Columbia VON 1G0, Canada; Behavioural Ecology Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada |
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Abstract: | The notion that predators can affect their prey without killing them is widely supported in the ecological literature yet rarely applied by marine mammal studies. We present three case studies in which patterns of time allocation by individual marine mammal foragers were used to index the sublethal effects of predators on bottlenose dolphins (Tursiops sp.), harbor seals (Phoca vitulina), and dugongs (Dugong dugon). In each case, foraging individuals optimized energy gain and safety from predators by spending less time in more profitable but dangerous patches or decreasing their use of risky feeding tactics that would increase net energy gain. By implication, marine mammals are subject to the non consumptive effects of their predators (i.e., to intimidation), and fear can mediate their impacts on their resources. We suggest, therefore, that future studies quantify patterns of time allocation to measure sublethal effects of predators on marine mammals, as well as the capacity of marine mammals to have sublethal effects on their own prey. We argue that such an approach is important because non consumptive effects may be of greater magnitude than lethal effects of predators, and information on sublethal effects of predators can inform conservation plans and studies of community structure. |
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Keywords: | bottlenose dolphin Tursiops dugong Dugong dugon harbor seals Phoca vitulina intimidation predation risk time allocation trait-mediated indirect interactions |
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