Almost all species of bears hibernate , spending most of the winter in their dens, sleeping in a dormant state, awaiting the arrival of spring, the heat and the flowering of nature. The phenomenon has been studied by scientists. How do they manage to survive for so many months without eating or drinking or urinating, doing nothing but sleep?
The Washington State University team has used an echocardiogram and analyzed heart tissue from bears and found that proteins in the heart change to match the slow rate of heartbeat when bears hibernate. The contractions of the heart muscle are controlled by a protein called myosin. This protein comes in two varieties: alpha, which produces a faster but weaker heartbeat, and beta. When they hibernate, the muscle in the left atrium of the heart of bears produces more alpha protein, so that the beat is weaker and does not damage the heart.
Hibernation of the Bear
An article has been published in the journal Physiological and Biochemical Zoology that explains what happens to the heart of bears when they hibernate and that explains the phenomenon. The heart of bears undergoes some changes in grizzly bears ( Ursus arctos horribilis ), the species of bear that has been studied by scientists.
This particular species hibernates between five and six months a year. During that time, the heart rate drops from the normal rate, a speed of about 84 beats per minute, to 19 beats per minute. Many animals, including humans, would be on the brink of death if their heart rate dropped to that level. But bears live. They not only live, they need it to get through the winter.
Such a slow heartbeat , logically, causes the blood flow to be altered, with fatal consequences. For example, the atria and ventricles could become flooded. In a person, these cavities would expand and the muscle would be weaker and less efficient. Eventually, heart failure would occur and death would ensue. However, this is not what happens to bears. Now they have discovered why.