Seasonal pattern and energetics of short daily torpor in the Djungarian hamster, Phodopus sungorus.

In Phodopus sungorus spontaneous shallow daily torpor occurred only during winter. Frequency of torpor was not affected by low ambient temperature but the seasonal cueing seems primarily dependent on photoperiodic control. Maximum torpor frequency was found in January with 30% of all hamsters living inside or outside being torpid at a time. It is calculated that torpor will reduce long term energy requirements of Phodopus by only 5%. Therefore it is concluded that torpor is not primarily aimed to reduce energy requirements but to guarantee survival of a fraction of a population during short periods of extreme cold load or inaccessability of food.