Twenty-four macaroni penguins (Eudyptes chrysolophus) from three groups, br
eeding 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 (s(V)over dotO(2)) were recorded from the anima
ls, and both fH and s(V)over dotO(2) were found to increase linearly with i
ncreasing treadmill speed. A linear regression equation described the relat
ionship between fH and s(V)over dotO(2), 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 s(V)over dotO(2), were recorded fro
m five of these animals for a total of 24 h, When fH was used to predict s(
V)over dotO(2), for the 24 h period using the derived regressions, the esti
mate was not significantly different from the measured values, with an aver
age error of -2.1 %. When fH was used to predict s(V)over dotO(2), 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/s(V)over dotO(2), 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 a
re taken into account,fH can be used to predict the metabolic rates of free
-ranging macaroni penguins all year round.