Hibernation is a curious thing that is still not fully understood by biologists even today. They may understand why animals hibernate, but not how they manage to do it, and for so long.
Many creatures, including insects, reptiles, amphibians, and birds, either hibernate or go into a similar state of inactivity during cold weather. But perhaps the most fascinating are the hibernating mammals.
Unlike most of these other creatures, with the exception of birds, mammals are warm-blooded. Their core body temperature must remain regulated to stay healthy. Yet during hibernation, body temperature plummets, often mirroring that of the surrounding air temperature.
The most common reason for any species to hibernate is to survive the bleak winter months which often means a scarcity of food, as well as extreme cold that they may otherwise not be able to tolerate.
Hibernation differs greatly from ordinary sleep. Hibernation, or a less severe form of it called torpor, involves the animal becoming non-active, sometimes for as long as six months. The body basically shuts down, and the animal may appear to be dead. Heart rate, breathing, and metabolism slow way down and may even be undetectable to anyone not an expert. The animal is completely dormant, and yet entirely alive. They are basically in a state of suspended animation.
Prior to hibernating, the animal usually will stock up on food, eating much larger amounts of it to bulk up, as they will be living entirely on their fat stores. Most will retreat in a burrow, den, or other form of shelter, away from any predators.
Some animals such as bears are famous for hibernating. Yet bears enter torpor rather than true hibernation. This means that they can re-awaken fairly easily and may do so periodically to relieve themselves, eat, or drink before going back into a dormant state. Bears are easily disturbed, and are still dangerous even in this state.
A truly hibernating creature will be unaware if someone or something touches or moves it. Still, it is not a good idea to handle any potentially dangerous wild animal even if it appears oblivious to anything going on around it. Common sense applies here.
Many mammals such as certain rodents, bats, badgers, skunks, as well as the aforementioned bears, become dormant in winter. Since most of these animals can be dangerous, should you come upon any such hibernating creature, no matter how 'out of it' it may seem, leave it well enough alone. Intriguing and tempting as studying them up close may be, it's better to play it safe.