Well this winter is turning out to be quite the season. First it pounded us with the snow. Now it seems that the thermometer rarely rises into the double digits on the positive side. I recently read that the lake ice is covering more than 85 percent of Lake Superior.
That probably explains why we haven't been seeing much for lake effect snow lately. It also doesn't seem to be buffering us from the cold jet stream coming down from Canada. You have that cold temperature mixed in with a little bit of a breeze and I can understand why many folks and creatures migrate to warmer climates. It also makes sense why some of the critters and perhaps folks as well, go into a dormant state of hibernation.
There is a lot of debate as to what can be technically defined as hibernation. I'm not sure it will ever be settled, but basically it is period of dormancy with slowed metabolism. These periods can be very short to over a year in some cases. These periods are typically a way to survive times of cold or scarcity of food. For us, I think we can assume it's to get through the winter. Hibernation usually starts with the animal finding a suitable "hibernaculum" that protects them from the elements and predators. For me, that would be my bed surrounded with a pile of good books. For something like a small rodent, it's a burrow or nest. The animal then remains there till the stress is over.
Bears seem to be at the front and center of the hibernation debate. They do fatten up before winter and spend their time in a den. They even drop in body temperature and their metabolism slows. They don't ever drop to ambient temperature, only a few degrees, and will rouse if disturbed. That is part of the debate, but also, the sows give birth to cubs around this time of year and feed them till spring so there is some activity going on under that snow.
Skunks, although they don't birth during the winter, behave much like bears and are also part of the hibernation debate.
Other critters have less of a debate over their true hibernation. Smaller rodents will drop to nearly freezing for extended periods during their hibernation. They do occasionally warm themselves up and possibly hit their cached food but then return to the dormant state till it warms up. The reptiles and amphibians in the area are interesting in their hibernation. Some frogs, notably the wood frog and spring peeper, nearly freeze solid. They survive this by filling their internal organs with high levels of glucose which acts as an antifreeze to protect their organs. Other more aquatic frogs will lay on the bottom of a body of water and go dormant till things warm up. There is apparently enough oxygen in the water to allow them to require little to no breathing.
Turtles also typically burrow into the mud on the bottom of a pond or stream.
They have specialized skin that allows oxygen absorption from the water that prevents them from drowning.