Fat King Penguins Are Less Steady on Their Feet

Abstract

Returning to the shore after a feeding sojourn at sea, king penguins often undertake a relatively long terrestrial journey to the breeding colony carrying a heavy, mostly frontal, accumulation of fat along with food in the stomach for chick-provisioning. There they must survive a fasting period of up to a month in duration, during which their complete reliance on endogenous energy stores results in a dramatic loss in body mass. Our aim was to determine if the king penguin’s walking gait changes with variations in body mass. We investigated this by walking king penguins on a treadmill while instrumented with an acceleration data logger. The stride frequency, dynamic body acceleration (DBA) and posture of fat (pre-fasting; 13.2 kg) and slim (post fasting; 11 kg) king penguins were assessed while they walked at the same speed (1.4km/h) on a treadmill. Paired statistical tests indicated no evidence for a difference in dynamic body acceleration or stride frequency between the two body masses however there was substantially less variability in both leaning angle and the leaning amplitude of the body when the birds were slimmer. Furthermore, there was some evidence that the slimmer birds exhibited a decrease in waddling amplitude. We suggest the increase in variability of both leaning angle and amplitude, as well as a possibly greater variability in the waddling amplitude, is likely to result from the frontal fat accumulation when the birds are heavier, which may move the centre of mass anteriorly, resulting in a less stable upright posture. This study is the first to use accelerometry to better understand the gait of a species within a specific ecological context: the considerable body mass change exhibited by king penguins.

Chatham Island Paleocene fossils provide insight into the palaeobiology, evolution, and diversity of early penguins (Aves, Sphenisciformes)

“…Modern penguins use their cornified feet and tarsometatarsi for much more than walking or resting, including propelling themselves in prone positions on land or ice, gripping and holding onto icy surfaces, and are also very important in underwater flight, assisting with steering the bird as it swims Stonehouse, 1967;Bedford, 1970;Hui, 1985;Parfitt and Vincent, 2005). It has also been observed that the presence, shape, and position of feet in extant penguins during underwater flight reduced drag and completed a more hydrodynamic shape (Parfitt and Vincent, 2005), and may potentially facilitate heat retention when feet are placed in line with the body (Willener et al, 2016). Effectively, the evolution of the distinctive shortened tarsometatarsi in some of the earliest penguins may have evolved as an adaptation that augmented swimming capabilities (Willener et al, 2016).…”

“…It has also been observed that the presence, shape, and position of feet in extant penguins during underwater flight reduced drag and completed a more hydrodynamic shape (Parfitt and Vincent, 2005), and may potentially facilitate heat retention when feet are placed in line with the body (Willener et al, 2016). Effectively, the evolution of the distinctive shortened tarsometatarsi in some of the earliest penguins may have evolved as an adaptation that augmented swimming capabilities (Willener et al, 2016). While this likely led to greater reproductive success (Willener et al, 2016), a consequence of such shortened-hind limbs may have meant Kupoupou stilwelli n. gen. et sp., ?Crossvallia waiparensis and the Waipara Greensand giant were prone to high metabolic costs while walking, but also large lateral displacement of their feet, characteristic of an energetically conservative waddling gait observed in modern forms (Pinshow et al, 1977;Gauthier-Clerc et al, 2000), compared to the relatively less phylogenetically derived Waimanu manneringi and Muriwaimanu tuatahi.…”

Frontal plane dynamics of the centre of mass during quadrupedal locomotion on a split-belt treadmill

“…The lateral control of balance is particularly important in bipedal locomotion, e.g. in walking ducks [6], penguins [7], non-human primates [8] and humans [9,10], where the moving animal is only supported by a single limb for most of the walking cycle. During phases of single-limb support, the body may be modelled as an inverted pendulum [11].…”

pamlr: A toolbox for analysing animal behaviour using pressure, acceleration, temperature, magnetic or light data in R

“…Although all of these sensors have previously been integrated into GPS tags with an increasing number of methods available for identifying behavioural states using such sensors, these analyses rely heavily on (a) movement data and precise location estimates to infer behaviour from turning angles (e.g. Garriga et al, 2016; Munden et al, 2019; Potts et al, 2018; Seidel et al, 2018; Williams et al, 2020), (b) multi‐second tri‐axial acceleration and bearing (Bidder et al, 2015; Hernández‐Pliego et al, 2017; Willener et al, 2016; Williams et al, 2017) and/or (c) validation datasets for supervised machine learning (Leos‐Barajas et al, 2017; Resheff et al, 2014). PAM loggers, however, (a) cannot provide spatial information to infer turning angles.…”