Ventilatory physiology of the numbat (Myrmecobius fasciatus).

This study examines the ventilatory physiology of the numbat (Myrmecobius fasciatus), a small to medium-sized (550 g) termitivorous marsupial. Ventilatory parameters at thermoneutrality reflect the slightly low (83% of predicted) basal metabolic rate of the numbat, with ventilation frequency (fR; 30.6+/-3.65 breaths min(-1)), tidal volume [VT; 6.0+/-0.66 ml at body temperature and pressure, saturated (BTPS)] and consequently minute volume (VI; 117.7+/-15.22 ml min(-1); BTPS) all being 80-87% of that expected for a marsupial of similar body mass. Oxygen extraction was 27.7+/-1.37% in the thermoneutral zone. As is typical of marsupials, numbats accommodated increased oxygen consumption rates at ambient temperatures (Ta) below the thermoneutral zone by increasing minute volume (up to 411.2+/-43.98 ml min(-1); BTPS at Ta=10 degrees C) rather than oxygen extraction. Minute volume at 10 degrees C increased more by changes in ventilation frequency (up to 45.5+/-4.85 breaths min(-1)) than tidal volume (9.4+/-1.03 ml, BTPS), as is also typical for a small-medium sized marsupial.