It is well known that the winter season introduces many changes in the way animals live and survive, such as the migration of whales, seals, turtles, eels, crabs, fish, butterflies, etc. Hibernation is a widely used term when referring to animals during the winter. Basically, animals hibernate in order to escape the harshness of time and lack of food in these months. They use it as a means to preserve the energy and heat of their body, which is naturally assisted by their own body system.True hibernation is a state of inactivity or deep sleep, to which some animals enter during the winter season. The animal's body goes through a number of changes, such as body temperature decreasing more than normal and heart palpitations and breathing slowing down dramatically. Contrary to popular belief, bears do not experience true hebernation, but enter a state of winter lethargy, in which their body temperature remains normal.
The bears enter this winter dormancy gradually, a process which follows if they are not disturbed; even in their sleep it is very easy to awaken them. This contrasts with the animals that really hibernate, which are very difficult to awaken and that fall asleep quickly. Before entering their winter shelter, bears must gain considerable weight. Accumulated fat is the only source that energizes their metabolic activity, providing the fluids they need.
The primary purpose of hibernation is, colloquially speaking, to skip the winter season, during which food is scarce. Thus, in order to conserve energy, bears do not eat, defecate, or urinate during their winter dormancy. However, when bears come out of their lethargy, they are much thinner than when they entered. Bears lose about 22% of their muscle strength during the 3 to 4 months without food they spend in hibernation.
SOME INTERESTING FACTS ABOUT HIBERNATION IN ANIMALS
The flow of oxygen to the gray matter of hibernating animals can decrease up to 2 percent from normal.
Metabolic activity and heart rate also plummet. The heart rate of a ground squirrel can drop from 300 beats per minute to three or four tics in the same amount of time during hibernation.
Not only winter hibernation: In tropical Madagascar, the fat-tailed dwarf lemur crawls through tree holes and sleeps for an average of seven months to cope with food and water shortages during the dry season.
Hibernation in warm weather, or estivation, is also used by lizards, snails and turtles.
Even fish can hibernate. Notothenia coriiceps, informally known as Antarctic cod, reduce their metabolism by two-thirds and hide under the seabed during the dark Antarctic winters.
A state of suppressed physiological activity is known as lethargy, and a handful of mice, bats and birds use it daily. The blonde-throated hummingbird can reduce its metabolism ten times during the night.
Hibernation is basically an extended form of lethargy, but lethargy alone does not qualify as hibernation.
Animals in a state of lethargy can lower their body temperature to surprising extremes. The Arctic squirrel cools to 27 degrees Fahrenheit.
Mammals that enter true hibernation have to find ways to warm up every few days or weeks.
A pregnant black bear can give birth without leaving hibernation. It doesn't even need to get up to take care of its young, but rather breast-feeds its cubs for months taking advantage of their stored fat reserves.
Tripping over a bear hibernating in the forest is more likely than you think. Some winter openly in 1.5-foot wide nests made of branches and foliage.
When spring arrives, or droughts end, most hibernators emerge from their dens or nests without significant muscle atrophy or loss of bone density.
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