Brain circuit that times a state of low metabolism could have implications for space travel

You have gone without food for days, and the temperature drops to near freezing. What do you do? For some animals, the answer is influenced by the brain's circadian clock. Hummingbirds, bats, and mice are among the animals that can enter torpor, which reduces body temperature and metabolism. Scientists suspected that the brain's circadian clock controls the timing of torpor, but until now the exact mechanism was not known.