Daily torpor during the active phase in free-ranging rock elephant shrews (Elephantulus myurus)

Abstract

In highly seasonal environments animals that use daily torpor usually do so during the rest phase. In subtropical and tropical environments, however, daily torpor may not necessarily be confined to the animals' rest phase. Animals may display torpor during the active phase. We investigated the daily rhythms and seasonal rhythms of body temperature (T_b) in normothermic and torpid free-ranging rock elephant shrews Elephantulus myurus at Weenen Game Reserve, KwaZulu-Natal, South Africa. T_bs were recorded using miniature dataloggers from May 2001 to May 2002. Daily patterns of T_b in normothermic E. myurus suggested polyphasic T_b patterns that nevertheless suggested a rest phase that was coincident with the daytime. When the elephant shrews used torpor, the lowest T_bs were observed during the night-time, such that torpor was used during the coldest part of the night and arousal was associated with the 3-h period around sunrise. We suggest that the principal benefit of a flexible daily rhythm of T_b was that it facilitated arousal by passive exogenous heating using ambient temperature cycles.