3 . Humans can make do with scarves, coats and gloves in cold weather. Some animals can hibernate (冬眠) for the winter. A new study finds that reptiles (爬行动物) and birds do something that is similar to hibernation, but a little different. In very cold weather, their body temperatures greatly drop into an energy-saving state in order to survive. The ability to thermoregulation (体温调节) for reptiles and birds is possible.

In Texas, where the city of Beaumont reached a low of 18 degrees Fahrenheit last month, it looked as if alligators (短吻鳄) had died of cold — yet alive in iced-over water. By ensuring their long noses stayed above the water line, the cold-blooded creatures were able to lower their body temperatures to survive the sudden short period of very cold weather. The process, in the case of cold-blooded animals like reptiles, is called brumation — it’s like a short state of hibernating. While in this state, reptiles become sleepy and they can go for a long time without eating or drinking. For example, alligators can be in brumation from just a few hours to months.

Like reptiles and mammals, birds can go into a state called torpor in order to save energy under very cold conditions. “Torpor is somewhere between a short sleep and hibernation,” said Justin Baldwin, a PhD candidate in biology at Washington University in St. Louis. Baldwin studied 29 species of hummingbirds living in Colombia. Researchers found that hummingbirds can enter into deep or shallow torpor, depending on several factors, including their size and weather conditions. In deep torpor, the birds are much more likely to be affected by disease. And what’s more, they would be easily harmed by their enemies.

Some bird lovers want to help the birds when they are in torpor. For example, the Bird Alliance of Oregon offers a few tips on how to keep the birds from danger.