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First published online September 9, 2005
Journal of Experimental Biology 208, 3451-3461 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01791

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Energetic costs of diving and thermal status in European shags (Phalacrocorax aristotelis)

Manfred R. Enstipp^1,*, David Grémillet¹ and Svein-Håkon Lorentsen²

¹ Centre d'Ecologie et Physiologie Energétiques, CNRS, 23 Rue Becquerel, F-67087 Strasbourg Cedex 2, France
² Norwegian Institute for Nature Research, Tungasletta 2, N-7485 Trondheim, Norway

View larger version (14K): [in a new window]   Fig. 1. Side view and dimensions of the dive trench and the set-up of the respirometry system within the laboratory container. The approximate underwater routes taken by the birds are indicated by the arrows, with arrowheads indicating the direction of locomotion.

View larger version (27K): [in a new window]   Fig. 2. Respirometry trace (A) and stomach temperature (B) of a European shag during a dive trial (post-absorptive). Arrows indicate when the bird entered and left the respirometry set-up. The trial lasted 32 min in water of 10.1°C. Note, the trace in A does not represent instantaneous metabolic rate but gives an indication of metabolic rate during a dive trial. See Materials and methods for details on how diving metabolic rate was calculated.

View larger version (24K): [in a new window]   Fig. 3. Metabolic rate of European shags during various activities. Basal metabolic rate (BMR) was measured in air temperatures between 10 and 19°C. All measurements in water were made at water temperatures between 5 and 13°C. Values are grand means ± 1 S.D., which were established from individual bird means. N=3 birds for all activities except `preening', where N=1 bird. Asterisks indicate a significant difference from BMR.

View larger version (16K): [in a new window]   Fig. 4. Metabolic rate of post-absorptive European shags during diving (triangles) and when resting on the water surface (circles) at various water temperatures. There was a significant negative relationship between metabolic rate and water temperature during diving. The regression line shows the average relationship for all shags, which takes into account variability between subjects. It is best described by y=28.461-0.671x (r2=0.69, N=3 birds, n=25 trials), where y is metabolic rate during diving and x is water temperature. During resting, there was a non-significant trend for metabolic rate to increase with a decrease in water temperature (N=3 birds, n=12 trials).

View larger version (14K): [in a new window]   Fig. 5. Stomach temperatures of European shags during rest at night and during the day and during diving. Values are grand means ± 1 S.D., which were established from individual bird means. N=3 birds. *Significantly different from day (rest) value. Significantly different from diving (peak) value.