How is torpor different from true hibernation?

In the context of biology, the terms torpor and hibernation are related but distinct states of energy conservation used by animals to survive adverse environmental conditions.12

Torpor

Torpor is a state of lowered body temperature and metabolic activity. It is a flexible, short-term response that can last for only a few hours—such as overnight in hummingbirds—or extend for longer periods. Because it is a temporary physiological adjustment, animals in a state of torpor can often transition back to full activity relatively quickly.12

True Hibernation

True hibernation is a more profound, sustained form of dormancy adopted by certain mammals to survive winter. Unlike general torpor, true hibernation involves:34
* Extreme Physiological Suppression: The animal’s body temperature drops significantly (often near 0°C), and respiration and heart rates slow to a level where the animal may appear dead.53
* Complex Preparation: True hibernators undergo significant metabolic and physiological adjustments, such as accumulating body fat and altering endocrine gland activity, before entering the state.54
* Controlled Arousal: While true hibernators can rouse themselves to feed or move about during brief intervals, the process of fully awakening from deep hibernation is gradual and energy-intensive, often requiring an hour or more.32

While the term "hibernation" is sometimes used loosely to describe any winter dormancy, true hibernation is a specialized adaptation that allows an animal to "turn off its thermostat" while retaining the ability to regulate its internal state when necessary.34