title: Bottlenose dolphins modify behavior to reduce metabolic effect of tag attachment.
abstract: Attaching bio-telemetry or -logging devices ('tags') to marine animals for research and monitoring adds drag to streamlined bodies, thus affecting posture, swimming gaits and energy balance. These costs have never been measured in free-swimming cetaceans. To examine the effect of drag from a tag on metabolic rate, cost of transport and swimming behavior, four captive male dolphins (Tursiops truncatus) were trained to swim a set course, either non-tagged (n=7) or fitted with a tag (DTAG2; n=12), and surface exclusively in a flow-through respirometer in which oxygen consumption VO₂ and carbon dioxide production (VO₂; ml kg(-1) min(-1)) rates were measured and respiratory exchange ratio (VO₂/resting VO₂) was calculated. Tags did not significantly affect individual mass-specific oxygen consumption, physical activity ratios (exercise /resting ), total or net cost of transport (COT; J m(-1) kg(-1)) or locomotor costs during swimming or two-minute recovery phases. However, individuals swam significantly slower when tagged (by ~11%; mean ± s.d., 3.31±0.35 m s(-1)) than when non-tagged (3.73±0.41 m s(-1)). A combined theoretical and computational fluid dynamics model estimating drag forces and power exertion during swimming suggests that drag loading and energy consumption are reduced at lower swimming speeds. Bottlenose dolphins in the specific swimming task in this experiment slowed to the point where the tag yielded no increases in drag or power, while showing no difference in metabolic parameters when instrumented with a DTAG2. These results, and our observations, suggest that animals modify their behavior to maintain metabolic output and energy expenditure when faced with tag-induced drag.
authors.affiliation: Massachusetts Institute of Technology-Woods Hole Oceanographic Institution Joint Program in Oceanography/Applied Ocean Science and Engineering, 77 Massachusetts Avenue, Cambridge, MA 02139, USA Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543, USA jvanderhoop@whoi.edu.
authors.forename: Julie M
authors.initials: JM
authors.lastname: van der Hoop
authors.affiliation: Texas A&M University Corpus Christi, 6300 Ocean Drive, Corpus Christi, TX 78412, USA.
authors.forename: Andreas
authors.initials: A
authors.lastname: Fahlman
authors.affiliation: Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hurst
authors.affiliation: Dolphin Quest Oahu, 5000 Kahala Avenue, Honolulu, HI 96816, USA.
authors.forename: Julie
authors.initials: J
authors.lastname: Rocho-Levine
authors.affiliation: University of Michigan, 2350 Hayward, Ann Arbor, MI 48109, USA.
authors.forename: K Alex
authors.initials: KA
authors.lastname: Shorter
authors.affiliation: University of Michigan, 2355 Bonisteel Boulevard, Ann Arbor, MI 48109, USA.
authors.forename: Victor
authors.initials: V
authors.lastname: Petrov
authors.affiliation: Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Moore
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D001696:Biomechanical Phenomena; D050681:Bottle-Nosed Dolphin / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism; D004734:Energy Metabolism; D057446:Hydrodynamics; D008297:Male; D010101:Oxygen Consumption; D005082:Physical Exertion; D013550:Swimming / Q000502:physiology*; D013686:Telemetry / Q000295:instrumentation*
chemical_list: D002245:Carbon Dioxide
keywords: Bio-logging; Cost of transport; DTAG; Drag; Respirometry; Tagging; Transmitter