Fig. 7. An approximate model of the change in the critical threshold T_a that triggers arousal (thermal cue for arousal; thick dashed line) over the rest phase (daytime) in male N. geoffroyi. Torpor is entered before or near dawn. Arousal and active rewarming of body temperature (solid line) from torpor is predicted to occur if and when T_a (thin dotted line) reaches the thermal cue for arousal. Bats re-enter torpor in response to cooling of T_a. Torpid bats arouse near dusk.