Which physiological change initiates arousal from hibernation when animal body temperature reaches near freezing?

💡 Explanation

Upon reaching a near-freezing threshold, non-shivering thermogenesis mediated by uncoupling protein 1 (UCP1) in brown adipose tissue is triggered because sympathetic nervous system activity increases, generating heat and stimulating metabolic rate. Thus, non-shivering thermogenesis occurs, as opposed to vasoconstriction, ventilatory increases, or osmotic changes which are more prominent during hibernation onset.

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