Scaling of swim speed and stroke frequency in geometrically similar penguins: they swim optimally to minimize cost of transport

Citation:
Sato, K, Shiomi K, Watanabe Y, Watanuki Y, Takahashi A, Ponganis PJ.  2010.  Scaling of swim speed and stroke frequency in geometrically similar penguins: they swim optimally to minimize cost of transport. Proceedings of the Royal Society B-Biological Sciences. 277:707-714.

Date Published:

Mar

Keywords:

accelerometer, adelie penguins, angles, buoyancy, depth, dives, emperor penguins, energy, free ranging, isometric model, morphology, predict, water

Abstract:

It has been predicted that geometrically similar animals would swim at the same speed with stroke frequency scaling with mass(-1/3). In the present study, morphological and behavioural data obtained from free-ranging penguins (seven species) were compared. Morphological measurements support the geometrical similarity. However, cruising speeds of 1.8-2.3 m s(-1) were significantly related to mass(0.08) and stroke frequencies were proportional to mass(-0.29). These scaling relationships do not agree with the previous predictions for geometrically similar animals. We propose a theoretical model, considering metabolic cost, work against mechanical forces (drag and buoyancy), pitch angle and dive depth. This new model predicts that: (i) the optimal swim speed, which minimizes the energy cost of transport, is proportional to (basal metabolic rate/drag)(1/3) independent of buoyancy, pitch angle and dive depth; (ii) the optimal speed is related to mass(0.05); and (iii) stroke frequency is proportional to mass(-0.28). The observed scaling relationships of penguins support these predictions, which suggest that breath-hold divers swam optimally to minimize the cost of transport, including mechanical and metabolic energy during dive.

Notes:

n/a

Website

DOI:

10.1098/rspb.2009.1515