title: Ultra-High Foraging Rates of Harbor Porpoises Make Them Vulnerable to Anthropogenic Disturbance.
abstract: The question of how individuals acquire and allocate resources to maximize fitness is central in evolutionary ecology. Basic information on prey selection, search effort, and capture rates are critical for understanding a predator's role in its ecosystem and for predicting its response to natural and anthropogenic disturbance. Yet, for most marine species, foraging interactions cannot be observed directly. The high costs of thermoregulation in water require that small marine mammals have elevated energy intakes compared to similar-sized terrestrial mammals [1]. The combination of high food requirements and their position at the apex of most marine food webs may make small marine mammals particularly vulnerable to changes within the ecosystem [2-4], but the lack of detailed information about their foraging behavior often precludes an informed conservation effort. Here, we use high-resolution movement and prey echo recording tags on five wild harbor porpoises to examine foraging interactions in one of the most metabolically challenged cetacean species. We report that porpoises forage nearly continuously day and night, attempting to capture up to 550 small (3-10 cm) fish prey per hour with a remarkable prey capture success rate of >90%. Porpoises therefore target fish that are smaller than those of commercial interest, but must forage almost continually to meet their metabolic demands with such small prey, leaving little margin for compensation. Thus, for these "aquatic shrews," even a moderate level of anthropogenic disturbance in the busy shallow waters they share with humans may have severe fitness consequences at individual and population levels.
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, Building 1131, C.F. Moellers Alle 3, 8000 Aarhus C, Denmark; Marine Mammal Research, Department of Bioscience, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark. Electronic address: danuta.wisniewska@bios.au.dk.
authors.forename: Danuta Maria
authors.initials: DM
authors.lastname: Wisniewska
authors.affiliation: Scottish Oceans Institute, East Sands, University of St Andrews, St Andrews KY16 8LB, Scotland.
authors.forename: Mark
authors.initials: M
authors.lastname: Johnson
authors.affiliation: Marine Mammal Research, Department of Bioscience, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark.
authors.forename: Jonas
authors.initials: J
authors.lastname: Teilmann
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, Building 1131, C.F. Moellers Alle 3, 8000 Aarhus C, Denmark.
authors.forename: Laia
authors.initials: L
authors.lastname: Rojano-Doñate
authors.affiliation: Scottish Oceans Institute, East Sands, University of St Andrews, St Andrews KY16 8LB, Scotland.
authors.forename: Jeanne
authors.initials: J
authors.lastname: Shearer
authors.affiliation: Marine Mammal Research, Department of Bioscience, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark.
authors.forename: Signe
authors.initials: S
authors.lastname: Sveegaard
authors.affiliation: Sound and Behaviour Group, Institute of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark.
authors.forename: Lee A
authors.initials: LA
authors.lastname: Miller
authors.affiliation: Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover, Werftstrasse 6, 25761 Buesum, Germany.
authors.forename: Ursula
authors.initials: U
authors.lastname: Siebert
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, Building 1131, C.F. Moellers Alle 3, 8000 Aarhus C, Denmark; Murdoch University Cetacean Research Unit, School of Veterinary and Life Sciences, Murdoch University, Perth, WA 6150, Australia.
authors.forename: Peter Teglberg
authors.initials: PT
authors.lastname: Madsen
mesh_terms: D000818:Animals; D003247:Conservation of Natural Resources; D003718:Denmark; D005260:Female; D020387:Food Chain; D008297:Male; D050741:Phocoena / Q000502:physiology*; D011235:Predatory Behavior