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Maneuverability by the sea lion Zalophus californianus: turning performance of an unstable body design

Frank E. Fish^1,*, Jenifer Hurley² and Daniel P. Costa³

¹ Department of Biology, West Chester University, West Chester, PA 19383, USA
² Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039-9647, USA
³ Department of Biology and Institute of Marine Sciences, University of California, Santa Cruz, CA 95064, USA

View larger version (12K): [in a new window]   Fig. 1. Plot of relative turning radius and turning velocity for two sea lions.

View larger version (18K): [in a new window]   Fig. 2. Relationship between turning rate and centripetal acceleration in two sea lions. Acceleration increased directly with turning rate. The shaded area represents limits of turning performance for cetaceans from data presented by Fish (2002).

View larger version (16K): [in a new window]   Fig. 3. Relationship between centripetal force and turning velocity for the two sea lions. Solid regression lines were computed by the least-squares method for each sea lion. Regressions were statistically significant at P<0.001. Regression equations are provided in the text.

View larger version (15K): [in a new window]   Fig. 4. Illustrations of the flipper design and location for the sea lion from lateral (A) and dorsal (B) views. The position of the center of gravity (CG) is indicated by the filled circle. Rotational and translational instabilities associated with a three-dimensional axis system are projected on the lateral view of the sea lion. Rotational instabilities include roll (rotation around the x-axis), pitch (rotation around the y-axis), and yaw (rotation around the z-axis). Translational instabilities include movement along the three axes as surge (x-axis), heave (y-axis) and slip (z-axis).

View larger version (127K): [in a new window]   Fig. 5. Body flexibility in the sea lion demonstrated by dorsal bending.

View larger version (14K): [in a new window]   Fig. 6. Comparison of the relationship between turning radius and turning velocity for two sea lions and cetaceans. Data for the sea lion are indicated by solid circles for the male and solid triangles for the female. The shaded area represents limits of turning performance for cetaceans from data presented by Fish (2002).