| Consequences of buoyancy to the maneuvering capabilities of a foot-propelled aquatic predator, the great cormorant (Phalcrocorax carbo sinensis). | |
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MedLine Citation:
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PMID: 18775938 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Great cormorants are foot-propelled aquatic divers utilizing a region of the water column where their underwater foraging behavior is affected by their buoyancy. While swimming horizontally underwater, cormorants use downward lift forces generated by their body and tail to overcome their buoyancy. Here we assess the potential of this swimming strategy for controlling maneuvers in the vertical plane. We recorded the birds swimming through a submerged obstacle course and analyzed their maneuvers. The birds reduced swimming speed by only 12% to maneuver and were able to turn upward and then downward in the sagittal plane at a minimal turning radius of 32+/-4 cm (40% body length). Using a quasi-steady approach, we estimated the time-line for hydrodynamic forces and the force-moments produced while maneuvering. We found that the tail is responsible for the pitch of the body while motions of the body, tail, neck and feet generate forces normal (vertically) to the swimming direction that interact with buoyancy to change the birds' trajectory. Vertical maneuvers in cormorants are asymmetric in energy cost. When turning upward, the birds use their buoyancy but they must work harder to turn downward. Lift forces generated by the body were always directed ventrally. Propulsion improves the ability to make tight turns when the center of the turn is ventral to the birds. The neck produced only a small portion (10%) of the normal vertical forces but its length may allow prey capture at the end of pursuit, within the minimum turning radius. |
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Authors:
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Gal Ribak; Daniel Weihs; Zeev Arad |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: The Journal of experimental biology Volume: 211 ISSN: 0022-0949 ISO Abbreviation: J. Exp. Biol. Publication Date: 2008 Sep |
Date Detail:
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Created Date: 2008-09-08 Completed Date: 2008-12-02 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0243705 Medline TA: J Exp Biol Country: England |
Other Details:
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Languages: eng Pagination: 3009-19 Citation Subset: IM |
Affiliation:
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Department of Biology, Technion, Haifa 32000, Israel. gal.ribak@gmail.com |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Biomechanics Birds / anatomy & histology, physiology* Female Foot / physiology Male Models, Biological Neck / physiology Swimming / physiology* Tail / physiology Video Recording |
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