Fig. 2. Histograms showing times of arousal (filled vertical bars) and times of re-entry into torpor (open vertical bars) by bats over their rest phase during exposure to a diurnal fluctuation in ambient temperature (T_a; shown at the top) that commenced heating at (A) 06:00 h, (B) 09:00 h or (C) 12:00 h. Bats were placed into respirometry chambers in the evening (T_a: 13°C) and all had entered torpor during the night or around the time of lights on. All bats aroused in response to passive rewarming when heating commenced at 09:00 h or 12:00 h. When heating commenced at 06:00 h, bats (n=3) remained in torpor throughout on 4 of 15 (27%) days. The horizontal black and white bars above indicate the photophase.