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The influence of locomotion on air-sac pressures in little penguins

D. F. Boggs^1,*, R. V. Baudinette², P. B. Frappell³ and P. J. Butler⁴

¹ Department of Biology, Hall of Sciences 258, Eastern Washington University, Cheney, WA 99004, USA,
² Department of Environmental Biology, University of Adelaide, Adelaide, South Australia 5005, Australia,
³ Department of Zoology, La Trobe University, Melbourne, Victoria 3083, Australia and
⁴ School of Biosciences, The University of Birmingham, Birmingham B15 2TT, UK

View larger version (36K): [in a new window]   Fig. 1. Differential pressure fluctuations occurring with wing beats indicated by contractions of the pectoralis and supracoracoideus muscles. A breath (marked) is associated with the penguin raising its head above the surface while still swimming. No abdominal muscle activity was apparent during swimming or with the expiratory phase of the breath shown here.

View larger version (15K): [in a new window]   Fig. 2. Posterior thoracic air-sac pressure exhibits fluctuations with steps as this penguin walks at 0.4 m s–1 on a treadmill. Footfall of the left foot was recorded by an observer pushing an event marker (signal down). Abdominal muscle activity is related to step cycle and may contribute to the pressure oscillations.