Activity seascapes highlight central place foraging strategies in marine predators that never stop swimming
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Background: Central place foragers (CPF) rest within a central place, and theory predicts that distance of patches from this central place sets the outer limits of the foraging arena. Many marine ectothermic predators behave like CPF animals, but never stop swimming, suggesting that predators will incur ‘travelling’ costs while resting. Currently, it is unknown how these CPF predators behave or how modulation of behavior contributes to daily energy budgets. We combine acoustic telemetry, multi-sensor loggers, and hidden Markov models (HMMs) to generate ‘activity seascapes’, which combine space use with patterns of activity, for reef sharks (blacktip reef and grey reef sharks) at an unfished Pacific atoll. Results: Sharks of both species occupied a central place during the day within deeper, cooler water where they were less active, and became more active over a larger area at night in shallower water. However, video cameras on two grey reef sharks revealed foraging attempts/success occurring throughout the day, and that multiple sharks were refuging in common areas. A simple bioenergetics model for grey reef sharks predicted that diel changes in energy expenditure are primarily driven by changes in swim speed and not body temperature. Conclusions: We provide a new method for simultaneously visualizing diel space use and behavior in marine predators, which does not require the simultaneous measure of both from each animal. We show that blacktip and grey reef sharks behave as CPFs, with diel changes in activity, horizontal and vertical space use. However, aspects of their foraging behavior may differ from other predictions of traditional CPF models. In particular, for species that never stop swimming, patch foraging times may be unrelated to patch travel distance.
Papastamatiou , Y , Watanabe , Y , Demsar , U , Leos-Barajas , V , Bradley , D , Langrock , R , Weng , K , Lowe , C , Friedlander , A & Caselle , J 2018 , ' Activity seascapes highlight central place foraging strategies in marine predators that never stop swimming ' , Movement Ecology , vol. 6 , 9 . https://doi.org/10.1186/s40462-018-0127-3
© The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
DescriptionThis work was supported by the Marisla Foundation, the Grants-in-Aids for scientific research from the Japan Society for the Promotion of Science (25850138), the Hawaii Undersea Research Laboratory/NOAA Coral Reef Conservation Program (NA05OAR4301108, NA09OAR43002), and the Pelagic Fisheries Research Program/Joint Institute for Marine and Atmospheric Research (NA09OAR4320075).
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