If you saw a hibernating animal you might think it was dead. Sleeping all winter takes preparation and animals that hibernate begin preparing for it in the fall. They try to put on as much fat as possible because they won t be eating much during the winter. Animals that hibernate also put on a special kind of fat, called brown fat. Brown fat works fast to deliver quick energy to an animal coming out of hibernation.
Hibernation is still a bit of a mystery for scientists.
Scientists have found a special substance in the blood of hibernating animals. If blood is taken from a hibernating ground squirrel in the winter and injected into an active squirrel in the spring, the active squirrel goes into hibernation. There are different kinds of hibernation. A woodchuck s heart rate goes from 80 beats a minute when active to 4 or 5 beats a minute when in hibernation. Its body temperature drops from 98 degrees Fahrenheit to 38 degrees Fahrenheit.