Heart rate and rate of oxygen consumption of exercising macaroni penguins

Abstract

Twenty-four macaroni penguins (Eudyptes chrysolophus) from three groups, breeding males (N=9), breeding females (N=9) and moulting females (N=6), were exercised on a variable-speed treadmill. Heart rate (fH) and mass-specific rate of oxygen consumption (sV̇O2) were recorded from the animals, and both fH and sV̇O2 were found to increase linearly with increasing treadmill speed. A linear regression equation described the relationship between fH and sV̇O2 for each individual. There were no significant differences in these regressions between breeding and moulting females. There were significant differences in these relationships between all females and breeding males. fH and sV̇O2 were recorded from five of these animals for a total of 24 h. When fH was used to predict sV̇O2 for the 24 h period using the derived regressions, the estimate was not significantly different from the measured values, with an average error of -2.1%. When fH was used to predict sV̇O2 for the 5 min intervals used for the calibration in all 24 birds, the estimate was not significantly different from the observed values, and the average error was only +0.47 %. Since the fH/sV̇O2 relationship was the same during periods of the annual cycle when the animals were inactive/fasting and active/foraging, it seems reasonable that, as long as sex differences are taken into account, fH can be used to predict the metabolic rates of free-ranging macaroni penguins all year round.