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First published online February 15, 2008
Journal of Experimental Biology 211, 699-708 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.009852

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Feeding kinematics, suction and hydraulic jetting capabilities in bearded seals (Erignathus barbatus)

Christopher D. Marshall^1,*, Kit M. Kovacs² and Christian Lydersen²

¹ Texas A&M University at Galveston, Department of Marine Biology, 5007 Avenue U, Galveston, TX 77551, USA
² Norwegian Polar Institute, N-9296 Tromsø, Norway

^* Author for correspondence (e-mail: marshalc{at}tamug.edu)

Accepted 6 December 2007

Feeding kinematics, suction and hydraulic jetting capabilities of bearded seals (Erignathus barbatus) were characterized during controlled feeding trials. Feeding trials were conducted both on land and in water, and allowed a choice between suction and biting, but food was also presented that could be ingested by suction alone. Four feeding phases, preparatory, jaw opening, hyoid depression and jaw closing were observed; the mean feeding cycle duration was 0.54±0.22 s, regardless of feeding mode (P>0.05). Subjects feeding on land used biting and suction 89.3% and 10.7% of the time, respectively. Subjects feeding in water used suction and hydraulic jetting 96.3% and 3.7% of the time, respectively. No biting behavior was observed underwater. Suction feeding was characterized by a small gape (2.7±0.85 cm), small gape angle (24.4±8.13°), pursing of the rostral lips to form a circular aperture, and pursing of the lateral lips to occlude lateral gape. Biting was characterized by large gape (7.3±2.2 cm), large gape angle (41.7±15.2°), and lip curling to expose the teeth. An excavation behavior in which suction and hydraulic jetting were alternated was used to extract food from recessed wells. The maximum subambient and suprambient pressures recorded were 91.2 and 53.4 kPa, respectively. The inclusion of suction data for phocids broadens the principle that suction feeding kinematics is conserved among aquatic vertebrates. Furthermore, bearded seals support predictions that mouth size, fluid flow speed, and elusiveness of prey consumed are among a suite of traits that determine the specific nature of suction feeding among species.

Key words: pinnipeds, feeding kinematics, suction feeding