Torpor expression and patterns in 3 sympatric rodents from Inner Mongolia.

The diversity of rodents in Asian deserts is high. Nevertheless, little is known about their use of daily torpor and hibernation, which are employed by many small mammals worldwide for energy and water conservation to permit survival under adverse environmental conditions. We quantified for the first time, using temperature transponders and data loggers, long-term torpor expression and patterns in sympatric desert hamsters Phodopus roborovskii, striped hamsters Cricetulus barabensis and 3-toed jerboas Dipus sagitta under controlled conditions. Animals were live-trapped in Inner Mongolia in August and held in captivity under short photoperiods and low ambient temperatures (T _as) for about 6 months. Both hamster species (~half of individuals) expressed spontaneous (food available) daily torpor. Daily torpor in desert hamsters was less frequent and shallower than that in striped hamsters, which also had longer torpor bouts during torpor at T _a 15.8 ± 0.4 °C. Only one individual jerboa entered hibernation spontaneously at T _a 6.2 ± 0.5°C, but all hibernated after food deprivation. The 2 hamster species only slightly changed their body mass during the acclimation, whereas jerboas greatly increased their body mass by 27.9% during the first 2 months of acclimation probably as a preparation for the hibernating season. Our data show that short photoperiod and moderately low T _a induces spontaneous daily torpor in the 2 hamster species, suggesting that it is used regularly in the wild. Hibernation in Jerboas occurred at T _a 6.2 ± 0.5 °C especially when food was withheld suggesting limited food availability is the proximate trigger of their hibernation.