Dr Andrew Trites
Heart rate as a monitor for metabolic rate in captive juvenile Steller sea lions (Eumetopias jubatus)
The potential use of heart rate to monitor energy expenditure in free-ranging Steller sea lions (Eumetopias jubatus) was investigated by establishing whether a relationship exists between heart rate (fH) and oxygen consumption in captive sea lions while swimming and resting.
Four trained Steller sea lions (2 males and 2 females; mass 87.4 -194.4 kg; ages 16 months–3 years) were equipped with a datalogger and two dorsal electrodes to record ECG (from which fH was calculated). Four styles of electrodes were developed and tested before selecting a final subcutaneous design. (measured with open-circuit respirometry) was simultaneously recorded while the previously-fasted animal was at rest within an enclosed dry metabolic chamber or while it swam in an enclosed swim mill against water currents of various speeds (0-1.5 m.s-1). The mean regression equation describing the relationship between fH (beats.min-1) and (ml.min-1.kg-0.73) for all four animals was = (0.68fH ± 0.07 s.e.) – (15.07 ± 6.20) (r2=0.72, p<0.01).
The possibility that the fH/ relationship could be affected by digestion was investigated by feeding one of the male Steller sea lions either 6 or 12 kg of herring prior to entering the swim mill. increased over time after ingestion, while heart rate usually remained stable or decreased. The resulting relationship, = (0.24fH ± 0.03) – (18.49 ± 02.68) (r2=0.19, p<0.01), differed significantly from the relationship derived while the animal was fasted, indicating that digestion may alter the relationship between fH and . Fasting and feeding intervals must therefore be taken into account when considering the use of fH/ relationships to estimate energy expenditure from heart rate of free-ranging sea lions.
The relationship demonstrated between fH and while fasting suggests that heart rate can potentially be used to monitor energy consumption in free-ranging Steller sea lions. However, additional research should be conducted to further elucidate how the relationship is affected by such factors as digestion, sex, stress, and development.
Heart rate as a monitor for metabolic rate in captive juvenile Steller sea lions (Eumetopias jubatus). McPhee, C.P. 2001. Masters thesis, University of British Columbia, Vancouver BC. 86 pages (PDF)
Predicting metabolic rate from heart rate for juvenile Steller sea lions Eumetopias jubatus.
McPhee, J.M., D.A.S. Rosen, R.D. Andrews and A.W. Trites. 2003.
Journal of Experimental Biology 206:1941-1951.