Otariids such as the Steller sea lion (Eumetopias jubatus) are among the most manoeuvrable of
marine mammals (expressed as a minimum turning radius and speed during manoeuvres). They
evolved in terrestrial and aquatic environments that are structurally complex, and feed on prey
that are an order of magnitude smaller than themselves. Compared to other aquatic organisms,
Steller sea lions have an unstable body design and are presumed to invoke swimming techniques
that reflect their need to be highly manoeuvrable. Detailed information was experimentally
obtained about the turning techniques employed by otariids through jointly analysing kinematic
and kinetic parameters measured from video recordings of three captive Steller sea lions.
Centripetal force and thrust production were determined by examining body movements
throughout a series of turns. Results showed that most of the thrust was produced during the
power phase of the stroke cycle of the pectoral flippers. As opposed to previous findings, very
little or no thrust was generated during initial abduction of the pectoral flippers and during the
final drag-based paddling style of the stroke cycle. Peak of the thrust force was reached halfway
through the power phase, while the centripetal force reached its maximum value at the
beginning of the power phase. Kinematic aspects of the manoeuvres changed with the tightness
of the turns and the initial velocities. The degree of dorsal flexion of the body changed with the
turning radius and the degree of flipper abduction varied with swimming speed. However, the
general manoeuvring technique and turning sequence remained the same in all the recorded
manoeuvres. Contrasting the turning performance of the Steller sea lion with a simple dynamic
model of unpowered manoeuvres in aquatic animals showed significant departures from model
predictions due to the hydrodynamic effects of body movements. Overall, the turning sequence
of the Steller sea lion was found to be very consistent, and their manoeuvrability was found to
come from their ability to vary the duration and intensity of movements within the turning
sequence.Science, Faculty ofZoology, Department ofGraduat