As the periods of daylight shorten and temperatures drop, certain animals produce a hormone that triggers hibernation. During this time, they enter a state of metabolic suppression – that is, their bodies slow down, reducing energy consumption by disabling nonessential functions and focusing on the minimum required to keep the animal alive.
How animals hibernate
While hibernating, breathing and heart rate are suppressed and the body temperature drops. This reduces the amount of energy wasted, keeping the animal warm, and puts nonessential organs into a state of stasis. Reducing blood flow to the extremities conserves the little body heat that is generated; small arteries in the skin constrict, restricting the amount of blood that can flow through and diverting most of it to the essential organs. This diversion of blood raises the blood pressure, helping to maintain adequate blood flow despite the fact that the heart rate has slowed down.