Buoyancy under control: underwater locomotor performance in a deep diving seabird suggests respiratory strategies for reducing foraging effort

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dc.contributor.authorCook, Timothée Ren_ZA
dc.contributor.authorKato, Akikoen_ZA
dc.contributor.authorTanaka, Hidejien_ZA
dc.contributor.authorRopert-Coudert, Yanen_ZA
dc.contributor.authorBost, Charles-Andréen_ZA
dc.date.accessioned2015-11-10T14:47:50Z
dc.date.available2015-11-10T14:47:50Z
dc.date.issued2010en_ZA
dc.description.abstractBACKGROUND: Because they have air stored in many body compartments, diving seabirds are expected to exhibit efficient behavioural strategies for reducing costs related to buoyancy control. We study the underwater locomotor activity of a deep-diving species from the Cormorant family (Kerguelen shag) and report locomotor adjustments to the change of buoyancy with depth. METHODOLOGY/PRINCIPAL FINDINGS: Using accelerometers, we show that during both the descent and ascent phases of dives, shags modelled their acceleration and stroking activity on the natural variation of buoyancy with depth. For example, during the descent phase, birds increased swim speed with depth. But in parallel, and with a decay constant similar to the one in the equation explaining the decrease of buoyancy with depth, they decreased foot-stroke frequency exponentially, a behaviour that enables birds to reduce oxygen consumption. During ascent, birds also reduced locomotor cost by ascending passively. We considered the depth at which they started gliding as a proxy to their depth of neutral buoyancy. This depth increased with maximum dive depth. As an explanation for this, we propose that shags adjust their buoyancy to depth by varying the amount of respiratory air they dive with. Conclusions/Significance Calculations based on known values of stored body oxygen volumes and on deep-diving metabolic rates in avian divers suggest that the variations of volume of respiratory oxygen associated with a respiration mediated buoyancy control only influence aerobic dive duration moderately. Therefore, we propose that an advantage in cormorants - as in other families of diving seabirds - of respiratory air volume adjustment upon diving could be related less to increasing time of submergence, through an increased volume of body oxygen stores, than to reducing the locomotor costs of buoyancy control.en_ZA
dc.identifier.apacitationCook, T. R., Kato, A., Tanaka, H., Ropert-Coudert, Y., & Bost, C. (2010). Buoyancy under control: underwater locomotor performance in a deep diving seabird suggests respiratory strategies for reducing foraging effort. <i>PLoS One</i>, http://hdl.handle.net/11427/14831en_ZA
dc.identifier.chicagocitationCook, Timothée R, Akiko Kato, Hideji Tanaka, Yan Ropert-Coudert, and Charles-André Bost "Buoyancy under control: underwater locomotor performance in a deep diving seabird suggests respiratory strategies for reducing foraging effort." <i>PLoS One</i> (2010) http://hdl.handle.net/11427/14831en_ZA
dc.identifier.citationCook, T. R., Kato, A., Tanaka, H., Ropert-Coudert, Y., & Bost, C. A. (2010). Buoyancy under control: underwater locomotor performance in a deep diving seabird suggests respiratory strategies for reducing foraging effort. PloS one, 5(3), e9839. doi:10.1371/journal.pone.0009839en_ZA
dc.identifier.ris TY - Journal Article AU - Cook, Timothée R AU - Kato, Akiko AU - Tanaka, Hideji AU - Ropert-Coudert, Yan AU - Bost, Charles-André AB - BACKGROUND: Because they have air stored in many body compartments, diving seabirds are expected to exhibit efficient behavioural strategies for reducing costs related to buoyancy control. We study the underwater locomotor activity of a deep-diving species from the Cormorant family (Kerguelen shag) and report locomotor adjustments to the change of buoyancy with depth. METHODOLOGY/PRINCIPAL FINDINGS: Using accelerometers, we show that during both the descent and ascent phases of dives, shags modelled their acceleration and stroking activity on the natural variation of buoyancy with depth. For example, during the descent phase, birds increased swim speed with depth. But in parallel, and with a decay constant similar to the one in the equation explaining the decrease of buoyancy with depth, they decreased foot-stroke frequency exponentially, a behaviour that enables birds to reduce oxygen consumption. During ascent, birds also reduced locomotor cost by ascending passively. We considered the depth at which they started gliding as a proxy to their depth of neutral buoyancy. This depth increased with maximum dive depth. As an explanation for this, we propose that shags adjust their buoyancy to depth by varying the amount of respiratory air they dive with. Conclusions/Significance Calculations based on known values of stored body oxygen volumes and on deep-diving metabolic rates in avian divers suggest that the variations of volume of respiratory oxygen associated with a respiration mediated buoyancy control only influence aerobic dive duration moderately. Therefore, we propose that an advantage in cormorants - as in other families of diving seabirds - of respiratory air volume adjustment upon diving could be related less to increasing time of submergence, through an increased volume of body oxygen stores, than to reducing the locomotor costs of buoyancy control. DA - 2010 DB - OpenUCT DO - 10.1371/journal.pone.0009839 DP - University of Cape Town J1 - PLoS One LK - https://open.uct.ac.za PB - University of Cape Town PY - 2010 T1 - Buoyancy under control: underwater locomotor performance in a deep diving seabird suggests respiratory strategies for reducing foraging effort TI - Buoyancy under control: underwater locomotor performance in a deep diving seabird suggests respiratory strategies for reducing foraging effort UR - http://hdl.handle.net/11427/14831 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/14831
dc.identifier.urihttp://dx.doi.org/10.1371/journal.pone.0009839
dc.identifier.vancouvercitationCook TR, Kato A, Tanaka H, Ropert-Coudert Y, Bost C. Buoyancy under control: underwater locomotor performance in a deep diving seabird suggests respiratory strategies for reducing foraging effort. PLoS One. 2010; http://hdl.handle.net/11427/14831.en_ZA
dc.language.isoengen_ZA
dc.publisherPublic Library of Scienceen_ZA
dc.publisher.departmentPercy FitzPatrick Institute of African Ornithologyen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.rightsThis is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.en_ZA
dc.rights.holder© 2010 Cook et alen_ZA
dc.rights.urihttp://creativecommons.org/licenses/by/4.0en_ZA
dc.sourcePLoS Oneen_ZA
dc.source.urihttp://journals.plos.org/plosoneen_ZA
dc.subject.otherBuoyancyen_ZA
dc.subject.otherBirdsen_ZA
dc.subject.otherSwimmingen_ZA
dc.subject.otherBiological locomotionen_ZA
dc.subject.otherAerial respirationen_ZA
dc.subject.otherAccelerationen_ZA
dc.subject.otherForagingen_ZA
dc.subject.otherSeabirdsen_ZA
dc.titleBuoyancy under control: underwater locomotor performance in a deep diving seabird suggests respiratory strategies for reducing foraging efforten_ZA
dc.typeJournal Articleen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceArticleen_ZA
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