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First published online April 8, 2004
Journal of Experimental Biology 207, 1615-1624 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00952

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Metabolic rates of captive grey seals during voluntary diving

Carol E. Sparling^* and Michael A. Fedak

Sea Mammal Research Unit, Gatty Marine Laboratory, University of St Andrews, St Andrews, Scotland, UK, KY16 8LB

View larger version (13K): [in a new window]   Fig. 1. Schematic diagram of the open-flow respirometry system. The arrows show the direction of air-flow through the system.

View larger version (7K): [in a new window]   Fig. 2. Schematic of the pool used in the measurement of diving metabolic rate. The entire surface of the pool is covered by aluminium mesh so that the seal can only surface and breathe in the box situated in one corner. The pool is divided into lanes using nets, so that during measurement the seals can travel a maximum of 168 m away from the breathing box. The depth of the pool is 2.5 m.

View larger version (14K): [in a new window]   Fig. 3. The distribution of dive and surface times for all dives from all eight seals (767 dives in total).

View larger version (11K): [in a new window]   Fig. 4. Frequency distribution of dive durations from satellite-tagged UK grey seals (total number of dives was >219 000 from 108 seals).

View larger version (8K): [in a new window]   Fig. 5. Diving metabolic rates (DMR) in relation to mass. Each point is the mean DMR of an individual seal (N=8 seals). The solid line is the line fitted by least-squares regression, weighted by the number of dives from each individual. The equation for this line is: log DMR = log mass (0.76-1.79) (r2=0.92, P<0.0001). The broken line represents Kleiber's prediction of BMR in terrestrial mammals.

View larger version (8K): [in a new window]   Fig. 6. Mean (+S.D.) metabolic rates (the multiple of the basal metabolism predicted by Kleiber's allometric equation; Kleiber, 1975) of seven grey seals during diving (DMR) or during rest (RMR) at the water surface. Resting values are for alert, inactive animals breathing continuously. These data are compared with values for the same individuals, on the same day, during diving. The difference is significant (paired t-test, t=3.86, P=0.003).

View larger version (56K): [in a new window]   Fig. 7. 3-D surface plot of the relationship between diving metabolic rate (DMR), dive duration and mean speed during a dive (from all dives from all animals). Surface fitted to data using running median smoothing of the values at neighbouring points.

View larger version (13K): [in a new window]   Fig. 8. Variation in metabolic rate as a function of dive duration. Metabolic rates are oxygen consumption over the whole dive plus surface period expressed as a multiple of Kleiber's (1975) predicted basal metabolic rate. Dives from all eight seals are shown.

View larger version (22K): [in a new window]   Fig. 9. Log-transformed diving metabolic rate (DMR) plotted against dive duration for all dives. Also indicated is the boundary defined by quantile regression of the 95th percentile plus upper and lower 95% confidence limits to this line. The regression is significant at P<0.05. The thick, broken line represents the relationship between maximum possible aerobic log DMR and dive duration, based on maximum utilisation of body oxygen stores during the dive.

View larger version (26K): [in a new window]   Fig. 10. Test of the model's predictions of post-dive oxygen consumption (O2). Each point is an individual dive, with a different symbol for each animal. The predicted post-dive O2 is the O2 predicted by the model for that dive using the model that was fitted excluding all the dives from that animal. The broken line represents a 1:1 relationship between predicted and observed oxygen consumption.