Data from: Kinematic and hydrodynamic analyses of turning manoeuvres in penguins: Body banking and wing upstroke generate the centripetal force

Penguins perform lift-based swimming by flapping their wings. Previous
kinematic and hydrodynamic studies have revealed the basics of wing motion
and force generation in penguins. Although these studies have focused on
steady forward swimming, the mechanism of turning manoeuvres is not well
understood. In this study, we examined the horizontal turning of penguins
via 3D motion analysis and quasi-steady hydrodynamic analysis. Free
swimming of gentoo penguins (Pygoscelis papua) at an aquarium was
recorded, and body and wing kinematics were analysed. In addition,
quasi-steady calculations of the forces generated by the wings were
performed. Among the selected horizontal swimming manoeuvres, turning was
distinguished from straight swimming by the body trajectory for each
wingbeat. During the turns, the penguins maintained outward banking
through a wingbeat cycle and utilized a ventral force during the upstroke
as a centripetal force to turn. Within a single wingbeat during the turns,
changes in the body heading and bearing also mainly occurred during the
upstroke, while the subsequent downstroke accelerated the body forward. We
also found contralateral differences in the wing motion; i.e., the inside
wing of the turn became more elevated and pronated. Quasi-steady
calculations of the wing force confirmed that the asymmetry of the wing
motion contributes to the generation of the centripetal force during the
upstroke and the forward force during the downstroke. The results of this
study demonstrate that the hydrodynamic force of flapping wings, in
conjunction with body banking, is actively involved in the mechanism of
turning manoeuvres in penguins.