Wikipedia defines hibernation as; "a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate."

From frogs to the tuatara (a lethargic lizard-like animal found in New Zealand), snakes (such as rattlesnakes and copperheads) to woodchucks, and ground squirrels to bears, hibernation is key to their winter survival.

According to the definition however, there are two types of hibernation. True hibernation and false hibernation (also known as torpor).

While the list for hibernating mammals is relatively small, the body temperatures of animals such as ground squirrels, marmots and woodchucks will 1.) plummet until only a few degrees above the cold climate, 2.) their breathing will drop from several hundred times a minute, to one in five minutes, 3.) their heartbeat will go from several hundred a minute to one or two beats a minute, 4.) they will move only slightly every few hours, although their muscles will retain their tone, and 5.) their digestive and excretory systems will continue to work.

So deep is this sleep, that often times the hibernating animal is insensible to sound or touch!

Several studies have also shown that this deep sleep seems to make the hibernators immune to many dangers. For example, in one case study scientist placed a hibernating marmot in an airtight jar filled with carbon dioxide. After four hours, the marmot had suffered no adverse effects from the experiment.

In addition, a sleeping hedgehog was immersed under water more than twenty times without drowning! - True hibernation at it's finest.

Compared to ground squirrels, frogs (who hibernate in unfrozen mud at the bottom of lakes, rivers, and ponds), snakes (who hibernate in hollow logs, caves or dens), and other true hibernators however, the hibernation pattern of many bears is only a series of naps.

Since the body temperature of bears remains high (which burns an estimated 4,000 food calories a day) and their breathing remains at a normal rate, their winter sleep can easily be disturbed. Some bears even wake up during their winter nap and prowl around for hours, sometimes days. Thereby, making bears (even chipmunks) mammals that are not true hibernators (or torpor).

Although able to exist for three months or more without food or water; during the Bear's entire hibernating time, he/she neither urinates or defecates. While this can seem quite dangerous (since accumulated waste could cause uremic poisoning), the bear has a built-in waste-disposal recycling system.

Essentially, this process involves the bear diverting nitrogen from pathways, that combines urine into pathways that produce amino acids and new proteins. This process is completed when metabolized fats and recycled nitrogen are used as building blocks.

In retrospect, whether creatures in the animal kingdom participate in true hibernation or false (torpor), it's main purpose is ultimately met; to sucessfully survive the harsh effects of winter.