Emperor penguin oxygen consumption, heart rate and plasma lactate levels during graded swimming exercise

Oxygen consumption (V˙O•), heart rate and blood chemistry were measured in four emperor penguins, Aptenodytes forsteri (Gray), during graded swimming exercise. The maximum V˙O • obtained, 52 ml O2 kg21 min21, was 7.8 times the measured resting V˙O • of 6.7 ml O2 kg21 min21 and 9.1 times the predicted resting V˙O•. As the swimming effort rose, a linear increase in surface and submerged heart rates (fH) occurred. The highest average maximum surface and submersion heart rates of any bird were 213 and 210 beats min21, respectively. No increase in plasma lactate concentrations occurred until V˙O • was greater than 25 ml O2 kg21 min21. At the highest V˙O • values measured, plasma lactate concentration reached 9.4 mmol l21. In comparison with other animals of approximately the same mass, the aerobic capacity of the emperor penguin is less than those of the emu and dog but about the same as those of the seal, sea lion and domestic goat. For aquatic animals, a low aerobic capacity seems to be consistent with the needs of parsimonious oxygen utilization while breath-holding