A. Example of dynamic body acceleration (DBA) data in three axes for a king penguin walking during 15 seconds. B. The DBA data for the z axis over three seconds of the same data set.

<p>Open circles represent maximum values and closed circles indicate minimum values identified by an automated, custom-written program. These maxima represent the initial contact of one of the king penguin’s feet with the ground. The dashed lines indicate the calculations of DBA amplitude based on these maximum and minimum values. <b>Right:</b> Visual representation of the DBA axes and angle movements (Modified from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0147784#pone.0147784.ref016" target="_blank">16</a>])</p

Dynamic body acceleration recorded over time in a king penguin in the z (vertical) axis (full line), along with waddling angle amplitude (pointed line; positive numbers mean right incline, negative number left incline) and backward leaning angle amplitude (dashed line).

<p>A grey shaded area followed by an unshaded area comprises a stride of the left leg, starting at the initial contact of the foot with the ground, represented by a grey vertical line. The maximum and minimum leaning angles within two initial contacts (i.e. two ‘steps’) are represented by black circles, while the maximum and the minimum waddling angle during one stride are represented by white circles. (Modified from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0147784#pone.0147784.ref016" target="_blank">16</a>])</p

Theoretical change in the location of the centre of mass between light (left) and heavy (right) king penguins in a standing posture.

<p>This difference will produce a resultant force in heavy birds which may cause it to fall forward during each step. The greater momentum associated with this increased mass may cause an increase in variability in trunk motion.</p

The mean amplitude of DBA in each axis measured by an accelerometry instrumented to king penguins while walking at 1.4 km/hour, when light and when heavy.

<p>The mean amplitude of DBA in each axis measured by an accelerometry instrumented to king penguins while walking at 1.4 km/hour, when light and when heavy.</p

Fish_Phylogeny

Phylogeny used for the analysis by Killen et al. 2016, American Naturalist

Killen et al Am Nat Table S1

Data used for the analysis by Killen et al. 2016, American Naturalist