ABSTRACT
Various physiological and morphological adaptations, such as reproductive quiescence, reduced body weight, and improved fur insulation, enable small temperate zone rodents to reduce energy expenditure during winter. In several species, e.g., the Djungarian hamster (Phodopus sungorus) and the white-footed mouse (Peromyscus leucopus), many of these winter-adjustments are induced by the perception of a shortening photoperiod during fall. In this chapter, the authors adopt a new approach to evaluate the role of daily torpor as an energy saving mechanism in Djungarian hamsters. They focus on differences between individuals in the incidence of torpor episodes and the concomitant consequences for long-term energy requirements. To address the problem of possible interactions between daily torpor and nocturnal activity, the authors measure temporal patterns of activity and feeding in long day and short day-adapted hamsters. They subsequently monitor body temperature, locomotion, and oxygen consumption in short-day housed animals to evaluate the relation between torpor-tendency, nocturnal activity, and metabolic rate.
