The influence of ambient temperature on spontaneous daily torpor in pouched mice ( Saccostomus campestris: Rodentia—cricetidae) from Southern Africa

Abstract

1. 1.|Eighteen pouched mice ( Saccostomus campestris), from three different localities in southern Africa, responded to a daily decline in ambient temperature ( T a) from 20 to 5°C by increasing metabolic heat production, thermolability and entering bouts of torpor. 2. 2.|The incidence of torpor increased with decreasing T a although torpor was only observed in a total of 8 individuals at temperatures below those prevailing in their winter burrows. 3. 3.|The minimum body temperature ( T bmin) of torpid individuals ranged between 30.0 and 21.0°C, but metabolic heat production during torpor increased to maintain T bmin as T a declined. 4. 4.|Torpor duration was correlated with minimum oxygen consumption V ̇ O 2min , but the energy savings associated with torpor were not correlated to either torpor duration, T bmin or V ̇ O 2min . 5. 5.|Individuals from all three localities entered torpor, while there appeared to be some geographical variation in the expression of torpor. 6. 6.|Male pouched mice had significantly lower values of T bmin and V ̇ O 2min than females and 6/9 males entered torpor compared to 2/9 females.