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1. Thermoregulatory behavior of fed and fasted desert hamsters (Phodopus roborovskii) acclimated to summer- [16 light (L):8 dark (D), ambient temperature (T-a) = 26.5 degrees C] and winter-like (8L-:16D, T-a = 10 degrees C) conditions was studied. Body temperature (T-b), selected temperature and activity were measured in hamsters placed in a thermal gradient system for 48 h.

2. Acclimation to winter-like days led to the decrease in body mass by 14% and in body temperature by 1 degrees C. On the contrary, selected T-a was higher by about 3 degrees C than in summer-like acclimated hamsters. Fasting affected only temperatures selected by night in winter-like acclimated hamsters.

3. Winter-like acclimation led to physiological changes, which may facilitate surviving long winter season. In the face of food shortage, behavioral thermoregulation may markedly reduce the energetic cost of normothermy. (c) 2007 Published by Elsevier Ltd.