How accurately can we estimate energetic costs in a marine top predator, the king penguin?
Résumé
King penguins (Aptenodytes patagonicus) are one of the greatest consumers of marine resources. However, while their influence on the marine ecosystem is likely to be significant, only an accurate knowledge of their energy demands will indicate their true food requirements. Energy consumption has been estimated for many marine species using the heart rate-rate of oxygen consumption [Formula: see text] technique, and the technique has been applied successfully to answer eco-physiological questions. However, previous studies on the energetics of king penguins, based on developing or applying this technique, have raised a number of issues about the degree of validity of the technique for this species. These include the predictive validity of the present [Formula: see text] equations across different seasons and individuals and during different modes of locomotion. In many cases, these issues also apply to other species for which the [Formula: see text] technique has been applied. In the present study, the accuracy of three prediction equations for king penguins was investigated based on validity studies and on estimates of [Formula: see text] from published, field f(H) data. The major conclusions from the present study are: (1) in contrast to that for walking, the [Formula: see text] relationship for swimming king penguins is not affected by body mass; (2) prediction equation (1), [Formula: see text] , derived in a previous study, is the most suitable equation presently available for estimating [Formula: see text] in king penguins for all locomotory and nutritional states. A number of possible problems associated with producing an [Formula: see text] relationship are discussed in the present study. Finally, a statistical method to include easy-to-measure morphometric characteristics, which may improve the accuracy of [Formula: see text] prediction equations, is explained.