*2.1. Animals and Groups*

All animal procedures and care and handling protocols were in accordance with the approval granted by the Laboratory Animal Care Committee of the China Ministry of Health (approval No. MH-55). The Daurian ground squirrels used in the experimental procedures were captured from the Weinan region, Shaanxi Province, China. Upon return to the laboratory, all squirrels were maintained in an animal room under a temperature range of 18–25 ◦C and modified daily light conditions (coincident with local sunrise and sunset). After one month of adaptation, the adult individuals were weight-matched and divided into six groups (n = 6–8): (i) Summer active group (SA): samples were collected in mid-June; (ii) pre-hibernation group (PRE): samples were collected in mid-September; (iii) late torpor group (LT): after two months hibernation, animals entered into a new hibernation bout and were in continuous torpor for at least 5 d, with a stable body temperature (Tb) of 5–8 ◦C; (iv) inter-bout arousal group (IBA): after two months hibernation, animals entered into a new hibernation bout and were fully aroused, with the Tb returned to 34–37 ◦C for less than 12 h; (v) early torpor group (ET): after two months hibernation, animals entered into a new hibernation bout, with Tb maintained at 5–8 ◦C for less than 24 h; (vi) post-hibernation group in spring (POST): animals awaking from hibernation and maintaining a Tb of 36–38 ◦C for more than 3 d in March of the following year. Animals in the SA and PRE groups were maintained in an environment with a natural light:dark photoperiod until sacrifice. When the ground squirrels gradually entered torpor in early November, the animals were transferred to a 4–6 ◦C dark hibernaculum. Due to observations occurring twice a day under weak light, these animals were housed under a 2:22 light-dark cycle. The Tb of animals was measured using a visual thermometer with thermal imaging (Fluke, VT04, Everett, Washington, DC, USA). The different states of the animals used here are shown in Figure 1.

**Figure 1.** Representative images and sampling time of Daurian ground squirrels in different periods. SA, summer active; PRE, pre-hibernation; LT, late torpor; IBA, inter-bout arousal; ET, early torpor; POST, post-hibernation.
