Cardiorespiratory and metabolic changes during hypoxic flight in bar‐headed geese (879.20)

The bar‐headed goose ( Anser indicus ) undergoes a biannual migration over the Himalayas, sustaining aerobic flight above 6,000 meters. The goal of our study was to collect cardiorespiratory and metabolic data during flight from geese flying in a wind tunnel in normoxia and two levels of hypoxia simulating altitude. In birds at rest, metabolic rate fell from 26.6 ± 1.3 mL min ‐1 kg ‐1 to 10.0 ± 0.9 mL min ‐1 kg ‐1 and 10.7 ± 4.8 mL min ‐1 kg ‐1 in normoxia, 10.5% O 2 and 7% O 2 respectively. It rose to 209.8 ± 5.2 mL min ‐1 kg ‐1 during flight in normoxia but decreased to 181.7 ± 5.0 mL min ‐1 kg ‐1 in 10.5% O 2 and to 131.7 ± 7.1 mL min ‐1 kg ‐1 in birds during flight in 7% O 2 . We found no change in heart rate across oxygen levels at rest or in flight. Heart rate at rest averaged 116.3 ± 35.4. While in flight, for any given metabolic rate we found a large range of heart rates in some individuals (184.5 to 457.0) and a very small range of heart rates in other individuals (256.8 to 375.7). There was, however, a strong positive correlation between metabolic rate and O 2 pulse (stroke volume x arterial‐venous O 2 content difference) at rest (slope=109.71; R 2 =0.57635) and in flight (slope=187.27; R 2 =0.65285) independent of the level of inspired O 2 in all birds. It appears that the bar‐heads increase metabolic efficiency during hypoxic flight and match O 2 supply to O 2 demand by a general increase in heart rate and specific increases in O 2 pulse. Grant Funding Source : NSERC of Canada; NSF, USA