CARDIOPULMONARY RESPONSES OF BURROWING OWLS (ATHENE CUNICULARIA) TO ACUTE HYPERCAPNIA AND HYPOXIA

While breathing air, burrowing owls had heart rates and blood gases similar to those of other birds, but had lower blood pressures and higher plasma bicarbonate concentrations. Heart rate, blood pressure, and bicarbonate levels of burrowing owls did not change significantly with inspired CO2. However, owls inhaling gases with a P1CO2 > 20 Torr had significantly elevated PaCO2 and PaO2 and were acidotic. Plasma bicarbonate concentration of burrowing owls declined significantly at P1O2 < 68 Torr, but heart rate was unaffected by hypoxia. PaO2 and PaCO2 declined during hypoxia and birds became alkalotic. The normal in vivo buffer line of burrowing owls represents a buffering capacity (31.5 mMol/l/pH unit) exceeding that of most birds, except divers. The cardiopulmonary responses of burrowing owls to hypercapnia and hypoxia are like those of non-burrow dwellers.