Metabolism in diving birds: studies in the laboratory and the field

Abstract

Heart rate has long been used as an indicator of the major physiological responses that many animals show to submersion. With the advent of modern techniques, particularly telemetry, it has been shown that the classical diving bradycardia, elicited by forced submersion, is not normally fully expressed during spontaneous diving. The classical bradycardia was shown to be a result of an oxygen-conserving response, the metabolic depression and associated anaerobiosis being easily demonstrated during forced submersion. Unfortunately, it is not yet feasible to measure directly the metabolic rate of voluntarily diving animals during the periods of apnoea. It is, however, possible to estimate oxygen consumption during a dive from the measurement of oxygen uptake between dives. By developing and using this technique, it has been shown that natural dives in two species of bird are primarily aerobic in nature. Anaerobic metabolism, previously thought to be of major importance during diving, now appears to be reserved for emergency situations.