Cardiovascular responses to diving and involuntary submergence in the rhinoceros auklet (Cerorhinca monocerata Pallas)

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Abstract
Cardiovascular responses during diving behaviour were recorded via a cannulated carotid artery in five rhinoceros auklets. Heart rate and mean arterial blood pressure were unchanged from predive values during both escape and feeding dives. The responses to feeding dives and escape dives did not differ. Acidosis, accompanying elevated steady-state plasma lactate levels during escape diving activity, was partially compensated by lung ventilation between dives. The absence of progressive accumulation of lactate in the blood implies that an aerobic steady state was attained, despite the short intervals between dives (2.4 ± 0.4 s). Arterial blood oxygen tension was maintained at reduced levels (50–60 mmHg; 1 mmHg = 133.322 Pa) for up to 32 min of continuous escape diving activity. Immersion of restrained auklets or capture of diving auklets in a net provoked a rapid and intense bradycardia. Growth of hand-reared auklet nestlings peaked at a time corresponding to the natural fledging age for this species but the urge to leave the nest box was not triggered by reduced food availability, as has been suggested for wild semi-precocial alcids. Potential pitfalls in the maintenance and use of alcids in physiological research are discussed.

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