We found some surprising answers: yes, humans can hibernate if needed, and maybe even on purpose! Tibetan monks can lower their oxygen needs about 60% when they are meditating. Scientists have isolated a gas called hydrogen sulfide that induces a hibernation-like state in mammals with only 10% of the oxygen needs during regular sleep. Could come in handy when traveling to Mars, or after a surgery to allow the body to heal. (Growth hormone releases increase during sleep which makes sleeping the time we do a lot of healing.)
The basic cycle of a hibernating bear in Minnesota - normal activity, hyperphagia (eating a lot), preparation for hibernation (by reducing food, but drinking more), hibernation and "walking hibernation" (the wake-up phase where low amounts of food are consumed) - is modified in warmer climates like North Carolina, where the bears will wake up several times during winter. And if weather gets too cold in Minnesota, the dropping temperatures in the bear's hibernaculum (or den) signal it to wake up and begin to shiver so it stays warm. So climate seems to play a role in whether or not a particular species hibernates in the traditional sense. But there are degrees of "sleepiness" based on where the animal lives.
We recorded how our pulse speeds up with activity and slows down with resting, as does our breathing rate. We tested how cold winter winds affect our body temperatures, and built a hibernaculum (winter shelter) to protect us.
Research question for the week is: What do you line the bottom of your den with in order to keep the cold from the earth from seeping up while you sleep? Hint: it creates air pockets.