Ventilation and oxygen extraction in the little penguin (Eudyptula minor), at different temperatures in air and water

Oxygen consumption, (VO2), carbon dioxide production (VCO2) and ventilation were measured in little penguins (Eudyptula minor) in air and water over a range of ambient temperatures. Barometrically measured minimum ventilation was very low (112 +/- 23 ml.min-1 over the range 15-20 degrees C, n = 9), principally due to a lower than predicted respiratory frequency (f) (6.9 +/- 1.1 min-1). This low ventilation resulted in a very high oxygen extraction (EO2) and low air convection requirement (VI/VO2). Despite large increases in metabolic rate in birds in cold water, VI/VO2 and hence EO2 did not vary in non-heat exposed penguins over a range of air and water temperatures. Mean extraction was 53.2 +/- 10.8% (n = 82) corresponding to an air convection requirement of 11.3 +/- 2.5 L.L-1. Above thermoneutrality there was a dramatic increase in ventilation and fall in EO2 resulting from increases in both f and tidal volume (VT). End-expired gases were measured at thermoneutrality and during heat exposure. At thermoneutrality FE'CO2 was 0.074 +/- 0.005, and FE'O2 0.115 +/- 0.009. During heat exposure end expired gases approached atmospheric levels.