Fig. 1.
Body temperature trace of a 13-lined ground squirrel from August through July of the following year. Seasonal and physiological groups are labeled; these colors are used throughout. Groups (n = 6) are fall active [FA: late September–mid-October, Tb = 32–37°C, 3 of these animals had not yet exhibited torpor (56), the other 3 had been torpid for short periods, no more than 7 h and with a minimum Tb of no less than 19°C]; fall torpor [FT: same dates as FA, except all had exhibited previous multiday torpor bouts of at least 2.5 days with Tb <10°C; 4 of these animals were torpid (Tb = 6–7°C) and the other 2 had Tb of 19 or 36°C]; early arousing (E-Ar: Tb = 6–12.8°C); interbout aroused (IBA: Tb ∼37°C, 3 h after inflection point demarking the end of rapid rewarming), entrance (Ent: Tb = 27–23°C); late torpor (LT: Tb = 5–6°C, time torpid = 80–95% of previous bout); spring dark (SpD: Tb = 37°C for >10 days after spontaneous termination of hibernation); summer active (SA: animals in July-August). Tb, body temperature.