The Conditions for Torpor
It is a curious thing that although lowered body temperature must be among the defining characteristics of mammalian hibernation (see Hoffman, 1964a), it is not so firmly entrenched in the animal’s biology as other aspects of the cycle. Reproductive rhythms (Johnson, Foster, and Coco, 1933) and weight rhythms may persist in hibernating species without the animals ever becoming torpid. Certain individuals never hibernate even when in a cold room (p. 200). The present chapter considers what factors, internal or external, necessary or sufficient, bring into action the mechanisms for lowering body temperature and controlling it during hibernation. The nature of these mechanisms and their probable location in the anterior hypothalamus was the subject of the last chapter. Now it is necessary to face up to the unpredictability of when these mechanisms will operate.
KeywordsGround Squirrel Arctic Ground Squirrel Periodic Arousal Hibernation Season Weight Cycle
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