Measurements were made of the relation between body temperature, respiration, diving pattern, and water temperature using three adult harp seals (Phoca groenlandica). Core temperature, ventilation, gas exchange, and diving pattern were not affected by water temperature ranging from 1.8 to 28.2 °C. The basal metabolic rate of the seals in this study was not significantly different than that predicted for terrestrial mammals of equivalent size. Expired heat loss and convective heat loss from the body accounted for 16% of the heat loss and were independent of water temperature. The remaining 84% of the heat was lost from the flippers which accounted for less than 14% of the surface area. Calculations of the ratio of convective heat transfer coefficients of the blubber layer indicate that internal conduction rather than external convection governed heat loss.
Assimilation efficiency of energy in juvenile harp seals was 92.5–95.0% of gross energy intake when fed Atlantic herring and 72.2% when fed shrimp. Faecal energy losses increased directly with intake. Metabolizable energy (ME) ranged from 85.5 to 88.7% of gross energy intake for a diet of herring. Urinary energy losses increased directly with apparent digestible nitrogen intake. Faecal and urinary losses were not affected significantly by feeding frequency. Urine excretion indicated that feeding causes a diuresis, associated with increased energy, nitrogen, and ash excretion. A significant interaction was found for rate of weight change between feeding frequency and energy intake. Seals lost more weight at energy intakes below their maintenance level when fed four meals rather than two meals per day. Differences in rate of weight change with feeding frequency were not observed at other levels of energy intake. Maintenance energy requirements were estimated at 2658 kcal ME daily for seals fed two meals per day and 3514 kcal ME daily when fed four meals per day. Seals required approximately 3 times as much shrimp as herring of high lipid content to meet their energy requirements.
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