How does hibernation differ from torpor in mammals?

• A. Hibernation is a short daily reduction in metabolism; torpor is prolonged winter dormancy.
• B. Hibernation is a daily rest with brief inactivity; torpor involves no decreases in metabolism.
• C. Hibernation occurs only in tropical climates; torpor only in polar climates.
• D. Hibernation is prolonged, deep winter dormancy; torpor is short-term, often daily reduction in metabolism.

Answer: (D)

The main idea here is that the difference between hibernation and torpor is about how long and how deep the animal slows down its metabolism. Hibernation is a long, deep state of winter dormancy, with body processes kept at a very low level for weeks or months, often with only occasional brief arousals. Torpor is a short-term, much more flexible energy-saving state that can last hours to days and is frequently daily in some species, allowing quick returns to normal activity when conditions improve.

So the correct description aligns with that pattern: hibernation is prolonged, deep winter dormancy; torpor is a short-term, often daily reduction in metabolism. The other statements mix up duration, whether metabolism decreases, or climate associations, which don’t fit how these states actually work.