Hibernation is an ingenious adaptation that some animals employ to survive difficult conditions in winter. This unit examines the differences between hibernation and torpor, and discusses the characteristic signs of hibernation behaviour. It explores the triggers that bring on hibernation, and whether internal signals or external season cues are predominant. It also examines the physiological adaptations that occur in hibernating animals. This unit builds on and develops ideas introduced in the openlearn unit on Animals at the extreme: the desert environment (S324_1). This study unit is just one of many that can be found on LearningSpace, part of OpenLearn, a collection of open educational resources from The Open University. Published in ePub 2.0.1 format, some feature such as audio, video and linked PDF are not supported by all ePub readers.