title: Great hammerhead sharks swim on their side to reduce transport costs.
abstract: Animals exhibit various physiological and behavioural strategies for minimizing travel costs. Fins of aquatic animals play key roles in efficient travel and, for sharks, the functions of dorsal and pectoral fins are considered well divided: the former assists propulsion and generates lateral hydrodynamic forces during turns and the latter generates vertical forces that offset sharks' negative buoyancy. Here we show that great hammerhead sharks drastically reconfigure the function of these structures, using an exaggerated dorsal fin to generate lift by swimming rolled on their side. Tagged wild sharks spend up to 90% of time swimming at roll angles between 50° and 75°, and hydrodynamic modelling shows that doing so reduces drag-and in turn, the cost of transport-by around 10% compared with traditional upright swimming. Employment of such a strongly selected feature for such a unique purpose raises interesting questions about evolutionary pathways to hydrodynamic adaptations, and our perception of form and function.
authors.affiliation: National Institute of Polar Research, Tachikawa 190-8518, Japan.|Department of Life Sciences, University of Roehampton, London SW15 4JD, UK.
authors.forename: Nicholas L
authors.initials: NL
authors.lastname: Payne
authors.affiliation: Faculty of Aerospace Engineering, Technion, Haifa 32000, Israel.
authors.forename: Gil
authors.initials: G
authors.lastname: Iosilevskii
authors.affiliation: College of Marine and Environmental Sciences, James Cook University, Cairns, Queensland 4878, Australia.
authors.forename: Adam
authors.initials: A
authors.lastname: Barnett
authors.affiliation: Ocearch, Park City, Utah 84068, USA.
authors.forename: Chris
authors.initials: C
authors.lastname: Fischer
authors.affiliation: MarAlliance, San Pedro, PO Box 283, Belize.
authors.forename: Rachel T
authors.initials: RT
authors.lastname: Graham
authors.affiliation: School of Veterinary and Life Sciences, Centre for Fish and Fisheries Research, Murdoch University, Murdoch, Western Australia 6150, Australia.
authors.forename: Adrian C
authors.initials: AC
authors.lastname: Gleiss
authors.affiliation: National Institute of Polar Research, Tachikawa 190-8518, Japan.|SOKENDAI (The Graduate University for Advanced Studies), Tachikawa 190-8518, Japan.
authors.forename: Yuuki Y
authors.initials: YY
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D057446:Hydrodynamics; D009068:Movement; D012754:Sharks / Q000502:physiology*; D013550:Swimming / Q000502:physiology*