ABSTRACT
Alternative strategies to survive the severe winter in mammalian hibernators are spending the winter solitarily or gregariously, or accumulating body fat or hoarding food in nests. Although chipmunks (Eutamias) are well known as hibernators hoarding food in nests, their hibernation has scarcely been studied. This chapter analyzes ecological factors affecting timing of hibernation commencement and of spring emergence in the Siberian chipmunk E. sibiricus. The date of commencement fluctuated year by year, and displayed a parallel shift between adult males and adult females. A similar tendency was found also in spring emergence. The fluctuation of commencement in adults of both sexes generally paralleled that of the commencement of snow cover in autumn; similarly emergence paralleled the date of snow cover disappearance in spring. High female density and air temperature may be related to hibernation commencement. Mortality during hibernation in solitary hibernators is higher for juveniles than for adults.
