Patterns of activity and inactivity in echidnas (Tachyglossus aculeatus) free-ranging in a hot dry climate: correlates with ambient temperature, time of day and season

Abstract

Echidnas occur throughout Australia. They exhibit daily fluctuations in body temperature (T_b) and use torpor to various degrees throughout much of their range. Echidnas elsewhere are commonly diurnal except during hot weather. This study used temperature-sensitive radio-transmitters to investigate the activity patterns and temperature relations of echidnas in the relatively hot, dry climate of south-west Queensland with respect to temperature and photoperiod.

During activity, echidnas were characterised by rising, but not necessarily high, T_bs. Activity was seen only within an ambient temperature range (as measured in a nearby Stevenson Screen: T_ss) of 9–33°C so that activity was seen during the day and at night during the cool weather but only at night in summer. Echidnas used caves, burrows and logs when inactive. T_bs of inactive echidnas declined except when affected by rising ambient temperatures, as determined within these shelters (T_a). In summer, T_bs of echidnas in these shelters changed little or rose with increasing T_a to levels even higher than in active echidnas.

Torpor was used by echidnas for periods up to nine days during winter and occasionally for up to one day during summer. Due to the difficulty of identifying the occurrence of torpor from T_b alone in warm conditions, the possibility that echidnas utilise torpor for less than one day remains inconclusive. Nevertheless, at least five bouts of torpor were identified in four (of eight) echidnas during winter/spring and two bouts of torpor from two echidnas in summer.