Hibernation

Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate.

Hibernating animals conserve energy, especially during winter when food is short, tapping energy reserves, body fat, at a slow rate.

It's the animal's slowed metabolic rate which leads to a drop in body temperature and not the other way around.

The first exhibit I'd like to present is the Animal Hibernation focusing on bears and their muscle tissues:

Animals that hibernate include bats, some species of ground squirrels and other rodents but the most famous considered hibernator is the bear. Many bears of northern regions are assumed to hibernate in the winter. While many bear species do go into a physiological state called hibernation or winter sleep, it is not true hibernation. In true hibernators, body temperatures drop to near ambient and heart rate slows drastically, but the animals periodically rouse themselves to urinate or defecate and to eat from stored food.

The body temperature of bears, on the other hand, drops only a few degrees from normal and heart rate slows only slightly. They normally do not wake during this "hibernation", and therefore do not eat, drink, urinate or defecate the entire period. Higher body heat and being easily roused may be adaptations, because females give birth to their cubs during this winter sleep.

It can therefore be considered a more efficient form of hibernation because they don't need to be awake through the entire period, but they are more quickly and easily awakened at the end of their hibernation. They have to stay in a den for the whole hibernation.

Bears Muscle tissue during hibernation:

One issue that has aroused curiosity between physiologists for years is how hibernating mammals, such as bears, avoid extreme muscle wasting during hibernation.

How does a mammal prevent its muscles from degrading after going for months without eating? A new study offers some clues. A group from the University of Barcelona studied hibernating bears and identified specific blood plasma components which prevent protein breakdown. The bears' metabolisms preferentially burn their stored fat and therefore preserve muscle mass that would otherwise be rapidly degraded and broken down for energy.

The researchers conducted an experiment in which they injected rats with bear plasma, and observed a 40% reduction in chemical reactions that cause animals consume muscles for energy.

The Second Exhibit- Hedgehogs Hibernation:

The triggers that cause hedgehogs to hibernate are cold and a lack of food, and males are thought to hibernate first, although they will wake up earlier than females.

Hedgehogs have two sorts of fat, brown and white - the white fat (which is about 1/3 the total body fat just before hibernation) supplies the energy during hibernation, while the brown fat supplies the energy used when the hedgehog may wake up for brief periods during the winter, and when the hedgehog comes out of hibernation in the spring.

If the hedgehog does not have sufficient fat stores, it will not survive hibernation - hedgehogs should weigh at least 700 grams (about 1 & 1/2 lbs) if they are to hibernate successfully.

Hedgehogs sleep in a nest or hibernaculum - the hedgehog brings grass and leaves to its nesting site, builds a pile and then burrows inside and turns round and round packing the leaves flat and ending up with walls up to 10cm thick. A new nest is built in this way every winter.