Prematurely induced arousal from hibernation alters key aspects of warming in golden-mantled ground squirrels, Callospermophilus lateralis

• Natural and prematurely induced arousal from torpor have been regarded as synonymous events by many hibernation researchers.
• Direct comparison of rewarming dynamics between natural and prematurely induced arousal revealed meaningful differences.
• Peak warming rates were greater during prematurely induced arousal, suggesting that regulatory constraints may be present during natural arousal.

Hibernation researchers have long been interested in the transitions between the dissimilar states of torpor and euthermy. Natural arousal from torpor occurs spontaneously with highly predictable timing. However, animals can also be induced to arouse prematurely in response to various disturbances. While many investigations have used natural and induced arousals synonymously, direct comparisons of these two types of arousal have been limited. We address the question of whether natural and prematurely induced arousals generate the same patterns of warming at the level of the whole organism. We compare the effects of ambient temperature on the dynamics of natural versus induced arousals. Arousal duration, maximum rewarming rate, and the variance associated with increases in body temperature differed between natural and induced arousals. Prematurely inducing arousal also alters the duration of the interbout aroused (IBA) period. We recommend that careful consideration be given to experimental design and data interpretation related to the arousal phase of a torpor bout.