Hibernating animals can go on living although their body temperature
falls to the same degree as the cold temperature outside. How do they manage this?
Mammals are warm-blooded. This means that under normal conditions,
their body temperature always remains constant because the natural thermostat in their
body keeps on regulating this temperature. However, during hibernation, the normal body
heat of small mammals, like the squirrel rat with a normal body heat of 40 degrees, drops
down to a little bit above the freezing point as if adjusted by some kind of a key. The
body metabolism slows down to a great extent. The animal starts breathing very slowly and
its normal heartbeat, which is 300 times a minute, falls to 7-10 beats a minute. Its
normal body reflexes stop and the electrical activities in its brain slow down almost to
undetectability.
One of the dangers of motionlessness is the freezing of tissues in very
cold weather and their being destroyed by ice crystals. Hibernating animals however are
protected against this danger thanks to the special features they are endowed with. The
body fluids of hibernating animals are retained by chemical materials having high
molecular masses. Thus, their freezing point is decreased and they are protected from
harm.