The effects of depth on the cardiac and behavioural responses of double-crested cormorants (Phalacrocorax auritus) during voluntary diving

摘要: SUMMARY Heart rate and dive behaviour were monitored in double-crested cormorants (Phalacrocorax auritus) during shallow (1 m) deep diving (12 m), after breathing different gas mixtures, to investigate the role of depth accompanying changes blood levels cardiac behavioural control voluntary diving. Pre-dive heart both shallow- deep-diving birds was approximately three times resting (137.9±17.5 beats min–1; mean ± s.d., N=5), falling abruptly upon submersion around 200–250 beats min–1. During diving, initial reduction followed by a secondary, more gradual decline, level. In contrast, stabilised at dives similar duration, significantly lower (163.2±14.0 beats min–1) than (216.4±7.7 beats min–1), but cases above value. The difference response is probably due an increase arterial oxygen tension (PaO2) descent phase (compression hyperoxia). Exposure hyperoxic mixture before increased rate, while exposure hypoxic tanks reduced rate. hypercapnic had no significant effect on We suggest that strongly influenced throughout dive. Dive duration unaffected alterations inspired composition, surface interval decreased exposure. most efficient pattern (highest dive/pause ratio) observed Our study suggests level powerful stimulus facilitates adjustments foraging are important components strategy allowing maximise time spent under water and, hence, potential time.