Date of Graduation

Summer 2026

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

Committee Chairperson

Frank Fish, PhD

Committee Member

Jennifer Maresh, PhD

Committee Member

Michael Rosario, PhD

Abstract

The fore- and hindflippers of the family Phocidae have been largely ignored with respect to their hydrodynamics, despite their unique motions for aquatic locomotion. Foreflippers, capable of spreading (abducting) during turning maneuvers, function as control surfaces that generate lift. Hindflippers are laterally alternated between a closed (adducted) leading flipper and an abducted trailing flipper, the latter playing a crucial role in propulsion by maximizing surface area and generating thrust during each stroke. Questions remain regarding the interaction between the leading flipper and the trailing flipper and whether the leading flipper aids or interferes with stability. This study investigates the hydrodynamics of fore- and hindflippers in three seals: harbor (Phoca vitulina), harp (Pagophilus groenlandicus), and grey (Halichoerus grypus) seals through analysis of lift (CL) and drag (CD) in abducted and adducted configurations. Flipper models, created by 3D scanning and printing, were tested in a flow tank with a multi-axis force transducer. Results show that abducted foreflippers generate higher CL (up to 1.39), supporting maneuverability, while adducted foreflippers reduce drag (0.24-0.33), favoring efficiency through streamlining. Hindflippers increased CL and L/D in abducted form (up to 2.65) compared to adducted (2.13), showing importance for thrust production. In the combined hindflipper model, CD  was reduced (0.02) while increasing CL, indicating that the leading flipper enhances streamlining without interfering with propulsion. Species differences suggest ecological adaptations, with harbor seals favoring maneuverability for coastal environments and grey seals relying on powerful thrust for the open ocean. These findings demonstrate how hydrodynamic mechanisms work in phocid locomotion.

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