Feeding kinematics, suction, and hydraulic jetting performance of harbor seals (Phoca vitulina)

Christopher D Marshall; Sven Wieskotten; Wolf Hanke; Frederike D Hanke; Alyssa Marsh; Brian Kot; Guido Dehnhardt

doi:10.1371/journal.pone.0086710

Feeding kinematics, suction, and hydraulic jetting performance of harbor seals (Phoca vitulina)

PLoS One. 2014 Jan 24;9(1):e86710. doi: 10.1371/journal.pone.0086710. eCollection 2014.

Authors

Christopher D Marshall¹, Sven Wieskotten², Wolf Hanke², Frederike D Hanke², Alyssa Marsh³, Brian Kot³, Guido Dehnhardt²

Affiliations

¹ Department of Marine Biology, Texas A&M University, Galveston, Texas, United States of America ; Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, United States of America.
² Institute for Biosciences, Sensory and Cognitive Ecology Group, University of Rostock, Rostock, Germany.
³ Department of Marine Biology, Texas A&M University, Galveston, Texas, United States of America.

Abstract

The feeding kinematics, suction and hydraulic jetting capabilities of captive harbor seals (Phoca vitulina) were characterized during controlled feeding trials. Feeding trials were conducted using a feeding apparatus that allowed a choice between biting and suction, but also presented food that could be ingested only by suction. Subambient pressure exerted during suction feeding behaviors was directly measured using pressure transducers. The mean feeding cycle duration for suction-feeding events was significantly shorter (0.15±0.09 s; P<0.01) than biting feeding events (0.18±0.08 s). Subjects feeding in-water used both a suction and a biting feeding mode. Suction was the favored feeding mode (84% of all feeding events) compared to biting, but biting comprised 16% of feeding events. In addition, seals occasionally alternated suction with hydraulic jetting, or used hydraulic jetting independently, to remove fish from the apparatus. Suction and biting feeding modes were kinematically distinct regardless of feeding location (in-water vs. on-land). Suction was characterized by a significantly smaller gape (1.3±0.23 cm; P<0.001) and gape angle (12.9±2.02°), pursing of the rostral lips to form a circular aperture, and pursing of the lateral lips to occlude lateral gape. Biting was characterized by a large gape (3.63±0.21 cm) and gape angle (28.8±1.80°; P<0.001) and lip curling to expose teeth. The maximum subambient pressure recorded was 48.8 kPa. In addition, harbor seals were able to jet water at food items using suprambient pressure, also known as hydraulic jetting. The maximum hydraulic jetting force recorded was 53.9 kPa. Suction and hydraulic jetting where employed 90.5% and 9.5%, respectively, during underwater feeding events. Harbor seals displayed a wide repertoire of behaviorally flexible feeding strategies to ingest fish from the feeding apparatus. Such flexibility of feeding strategies and biomechanics likely forms the basis of their opportunistic, generalized feeding ecology and concomitant breadth of diet.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Biomechanical Phenomena
Eating / physiology*
Feeding Behavior
Fishes
Male
Phoca / physiology*
Pressure

Grants and funding

This work was supported by a Texas A&M University International Research Travel Assistance Grant to CDM, a VolkswagenStiftung grant to GD, a DAAD German Academic Student Exchange Scholarship (Deutscher Akademischer Austausch Dienst, DAAD), the Cologne Zoo, the Texas A&M University Department of Marine Biology, the University of Rostock Institute of Biosciences, and the University of Bochum Department of Biology. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.