The body temperature and hibernation pattern of the chipmunk Eutamias sibiricus across various ambient temperature ranges

The aim of this research was to investigate the hibernation pattern of the Siberian chipmunk across a broad range of temperatures, to determine the optimal temperature for hibernation, and to assess their ability to hibernate in relatively low environmental temperatures. In late August, three chipmunks had thermochron temperature sensors (DS-1922L-F5) surgically implanted to monitor their body temperature. The hibernation cycles of four chipmunks were studied by altering the temperature in their nesting materials. When the animals were moved to an underground lab with a temperature of –4 °C, the difference between their body temperature and the surrounding temperature increased by nearly 8 °C, reaching 12 °C to 14 °C as the ambient temperature dropped further. The length of hypothermia periods decreased while the frequency of awakenings increased. The lowest recorded body temperature was at least 1 °C. The longest hypothermia durations occurred in chipmunks exposed to temperatures between –4 °C and 4 °C, lasting 226 to 283 hours (9.4 to 11.8 days). For two chipmunks hibernating at temperatures below –6 °C, the hypothermia intervals averaged 73 and 99 hours, while other individuals had intervals of 174 to 188 hours. The optimal hibernation temperature range for chipmunksin Yakutia is between –4 °C to –6 °C and +5 °C to +6 °C. Hibernation ceases at ambient temperatures above 12 °C to 14 °C. When temperatures drop below –6 °C to –10 °C, the hibernation rhythm changes, resulting in shorter hypothermia intervals,similar to those observed at higher positive temperatures. Thisresearch enhances our understanding of how relatively small mammals can hibernate in low ambient temperatures (down to –10 °C). The findings may also be relevant for comparative studies on the hibernation of other small winter-hibernating mammals, such as hamsters and dormice, weighing up to 100 grams.