MEPS 328:275-284 (2006)  -  doi:10.3354/meps328275

Electrocardiogram recordings in free-ranging gannets reveal minimum difference in heart rate during flapping versus gliding flight

Yan Ropert-Coudert1,*, Rory P. Wilson2, David Grémillet3, Akiko Kato1, Sue Lewis4, Peter G. Ryan5

1National Institute of Polar Research 1-9-10 Kaga, Itabashi-ku, Tokyo 173-8515, Japan
2School of Biological Sciences, University of Wales—Swansea, Singleton Park, Swansea SA2 8PP, UK
3Centre National de la Recherche Scientifique, Département d’Ecologie, Physiologie et Ethologie, Institut Pluridisciplinaire Hubert Curien, 23 rue Becquerel, 67087 Strasbourg Cedex 02, France
4Centre for Ecology and Hydrology, Banchory Research Station, Hill of Brathens, Banchory, Aberdeenshire AB31 4BW, UK
5DST/NRF Centre of Excellence at the Percy FitzPatrick Institute, University of Cape Town, Rondebosch 7701, South Africa

ABSTRACT: Gliding flight is one of the major features that allows flying animals to cover extensive distances while minimising their energy expenditures. This has been supported by studies recording heart rate as a proxy for energy expended, but the exact amount of flapping and gliding during flight is often not taken into account, making a genuine assessment of the heart rate evolution with flight modes problematic. We used miniature accelerometers and electrocardiogram recorders attached externally to free-ranging Cape gannets Morus capensis to examine how heart rate varies when birds use gliding or flapping flight. Flapping phases (in beats per minute; 255.5 bpm) showed consistently higher heart rates than gliding phases (217.2 bpm), with the changes in heart rate at the onset of a new phase (flapping or gliding) being almost instantaneous, irrespective of the duration of the subsequent phase. Surprisingly though, the difference between the heart rates measured during flapping and gliding flights only amounted to about 20%. Such a small difference does not accord with the fact that gannets are known to have elevated flight costs. This discrepancy suggests that heart rate and metabolic rate are not correlated linearly in M. capensis. Cardio-vascular adjustments, such as a variable stroke volume (following Fick’s law), might have evolved because local wind conditions and gannet foraging strategies are not always compatible with gliding flight.

KEY WORDS: Heart rate · Locomotion · Externally attached data-logger · Flap and glide flight · Sulidae · Morus capensis · Bio-logging

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