Daily Torpor Induced by Food Restriction in the Chinese Hamster, Cricetulus griseus

Daily torpor in small mammals can be triggered by a shortening of day length (spontaneous daily torpor), or by a reduced energy budget due to factors such as food deprivation (fasting-induced daily torpor). While some hamsters are known to enter torpor, and spontaneous daily torpor has been observed in the genus Cricetulus, it has been thought that the Chinese hamster (C. griseus) does not express torpor. In this study, we attempted to induce daily torpor in the Chinese hamster through food deprivation. We used 18 hamsters, dividing them into three groups (50% feeding, 25% feeding, and 0% feeding [fasting]), and conducted three trials of 24-h restricted feeding, with intervals for recovery. The results showed three torpor bouts within the trials: once in the 50% feeding group and twice in the 25% feeding group, but no bouts were observed in the fasting group. The mean daily minimum body temperature (Tb) decreased progressively across trials, with the lowest values being recorded during the third trial in all groups. This study reveals for the first time that fasting-induced daily torpor occurs in the genus Cricetulus, suggesting that species in this genus could use spontaneous and fasting-induced torpor mechanisms.