| Summary: | This study investigated whether exposure to low ambient temperature could be used as an alternative to exercise for calibrating heart rate ( f H) against rate of oxygen consumption ( V ˙ O 2 ) for subsequent use of f H to estimate V ˙ O 2 in free-ranging animals. Using the relationship between the oxygen pulse (OP, the amount of oxygen used per heart beat) and an index of body condition (or nutritional index, NI), a relationship between f H and V ˙ O 2 was established for resting king penguins exposed to a variety of environmental temperatures. Although there was a small but significant increase in the OP above and below the lower critical temperature (-4.9°C), there was no difference in the relationship obtained between the OP and body condition (NI) obtained above or below the lower critical temperature. These results were then compared with those obtained in a previous study in which the relationship between f H and V ˙ O 2 had been established for king penguins during steady-state exercise. The relationship between OP and NI in the present study was not significantly different from the relationship between resting OP and NI in the previous study. However, the relationship was different from that between active OP and NI. We conclude that, at least for king penguins, although thermoregulation does not affect the relationship between resting OP and NI, temperature cannot be used as an alternative to exercise for calibrating f H against V ˙ O 2 for subsequent use of f H to estimate V ˙ O 2 in free-ranging animals.
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