Torpor in the Echidna, Tachyglossus aculeatus

Abstract

Echidnas maintained at 5°C without food became torpid after varying lengths of time, with minimum values of body temperature (T_E) 5.5°C, heart rate seven beats per minute, and oxygen consumption 0.03 ml 0₂ per gm body wt per hour. Initially the torpid animals were able to arouse at ambient temperature (T_A) 5°C, requiring about 20 hr to return T_B to within the normal awake range of 26 to 29 °C. However, arousal from repeated periods of torpor generally required an increase in T_A. Similar torpor was observed in one echidna maintained at 10°C without food in the laboratory and in another burrowed in the field at ground temperature 9°C. In both T_B fell to within 0.5°C of T_A. Under these conditions repeated spontaneous arousals are possible. On the basis of these physiological data the echidna appears to be a true mammalian hibernator.