printed in Great Britain VENTILATION AND OXYGEN EXTRACTION IN THE BAT PTEROPUS GOULDII DURING REST AND STEADY FLIGHT

Tidal volume (VT) breathing frequency (/) and oxygen consumption(j£)8) were simultaneously measured in the bat Pteropus gouldii during quiet rest at 24 °C, and oxygen extraction (E) values were calculated from these data. VT and / were also measured at 24 °C from P. gouldii undertaking steady wind-tunnel flight at different speeds and angles, and this information together with appropriate POt data reported previously for this bat were used to calculate flight E values. The oxygen extraction of resting P. gouldii was similar to that of a resting non-flying mammal of comparable size but lower than that of a resting bird. P. gouldii increases VT and/almost equally in going from quiet rest to level flight to achieve a 17-fold increase in minute ventilation. Compared to the resting bat, flying P. gouldii hyperventilates its respiratory system relative to its metabolic requirements. The level flight VT of P. gouldii compares favourably with that expected for a flying bird of the same body mass, and represents almost 90 % of the total lung capacity predicted for a non-flying mammal of comparable size. Because of the increased breathing frequency during flight, the minute ventilation requirement of P. gouldii during level flight exceeds that predicted for a similar-sized flying bird. E values cal-culated for flying P. gouldii are significantly lower than those reported for birds flying at comparable temperatures and flight conditions