Distinguish torpor from hibernation and describe when each occurs.

• A. Torpor is a short-term daily drop in metabolic rate; hibernation is a sustained multi-day reduction.
• B. Torpor lasts weeks; hibernation lasts hours.
• C. Torpor occurs only in birds; hibernation in mammals.
• D. They are the same concept.

Answer: (A)

The key idea is that torpor and hibernation differ in how long and how deeply an animal lowers its metabolism. In torpor, the metabolic rate and body temperature drop briefly—typically on a daily basis—so the animal saves energy during short periods of cold or scarce food. It can wake up relatively quickly and resume normal activity. Hibernation, by contrast, is a prolonged state of energy saving that lasts days to weeks, with metabolism kept at a very low level and body temperature markedly reduced; arousals from this state are infrequent. This helps animals endure extended winters when food is scarce and conditions are harsh.

So the statement that torpor is a short-term daily drop and hibernation is a sustained multi-day reduction best captures the distinction. The other options mix up duration, applicability, or equate the two states as the same, which doesn’t fit how these energy-saving strategies actually operate.