GOLDBOGEN, J.A.; OLESON, E.M.; CALAMBOKIDIS, J.; SHADWICK, R.E.; MCDONALD, M.A.; HILDEBRAND, J.A.; Scripps Institution of Oceanography, University of California, San Diego; Scripps Institution of Oceanography, University of California, San Diego; Cascadia Research Collective, Olympia, WA; Scripps Institution of Oceanography, University of California, San Diego; Whale Acoustics, Bellvue, CO; Scripps Institution of Oceanography, University of California, San Diego; ; : Lunge-feeding kinematics of fin whales

Fin whales (Balaenoptera physalus) are fast streamlined swimmers that regularly dive to depths greater than 100 m to feed on small schooling fish and planktonic crustaceans. Lunge-feeding is the primary mechanism of prey capture employed by these whales where large amounts of seawater are engulfed and filtered. This feeding process is hypothesized to be energetically costly and consequently limit dive duration, which theoretically scales with body size. Optimality models of dive behavior from depth profiles support this hypothesis, but very little is known regarding the swimming mechanics of engulfment feeding. Here we quantitatively describe the kinematics of foraging dives of fin whales in the Southern California Bight. High-resolution digital tags, equipped with a hydrophone, a depth gauge, and accelerometers, were attached to the backs of surfacing whales between the blowhole and the dorsal fin. Rotational accelerations about two orthogonal body axes allowed for pitch and roll to be calculated and bouts of active fluking were interpreted from smaller amplitude oscillations in the accelerometer signals. Animal speeds during glides were calculated from depth profiles and body orientation over time; the magnitude of turbulent flow sensed by the hydrophone may serve as an additional index for speed. These kinematic parameters depict a dynamic mechanical process that involves rapid changes in rotational and translational acceleration.