The thermal physiology of the Mountain Pygmy-possum Burramys parvus (Marsupialia: Burramyidae).

Abstract

The Mountain Pygmy-possum Burramys parvus is restricted to the Australian alpine region. Laboratory studies of the thermo-physiology of this species found that body temperature (Tb) was tightly regulated at 36.1oC, but animals quickly become hyperthermic at ambient temperatures (Ta) above 30oC, causing the thermal neutral zone to be truncated. Basal metabolic rate was 2.15 W kg -0.75 (mean body mass 44.3 g) and weight-specific thermal conductance was 0.112 ml O2, g-1 h-1 oC-1. These values are 9% and 44% lower, respectively, than the mass predicted value for a marsupial, showing that the overall rate of energy expenditure is considerably reduced in this species. Huddling also reduces individual rates of energy expenditure. Burramys parvus enters prolonged bouts of deep torpor lasting up to one week, during which Tb is very low and close to Ta and the rate of oxygen consumption greatly reduced. Spontaneous arousal occurred from a Tb as low as 6oC and the overall rate of rewarming was 0.17 oC /min. Attainment of a critical body mass appeared to be necessary before an animal would enter torpor. Burramys parvus shows physiological adjustments similar to that described in many placental mammals from cold climates and this species represents a true marsupial hibernator.