Hibernation in the American Black Bear

Abstract

During recent years considerable interest has been shown in the study of hibernation. However, there seems to be some confusion as to the meaning of the word when applied to different Funk and Wagnalls's dictionary (1949) defines as the ability to the winter . . . in a secluded place and in a torpid state, as certain animals. Torpid is defined as lost, partially or wholly, sensibility or power of motion, as a hibernating animal. Thus the term hibemationi may include the partial loss as well as the whole loss of sensibility or power of motion. Dormant is described as being in a state resembling sleep; torpid; hibernating in a state of lethargy as bears and some other animals in winter. Lethargy is defined by the same authority as a state of complete repose or torpor as an animal hibernating. Although bears are generally considered to be the classical animal which demonstrate hibernation, some authors in recent years (Matson, 1946; Lyman and Chatfield, 1950) have questioned the fact that these camivores actually pass the winter in a state of hibernation. However, their interpretation of the word is somewhat different from that designated by Funk and Wagnall. Lyman and 'Chatfield state that for the purpose of their article, hibernation is defined as a condition characterized by a marked lowering of the body temperature with a concurrent drop in metabolism, heart rate, respiration and other vital functions. By this definition the most famous 'hibernating' animal, the black bear, does not hibernate at all. It is true that the bear spends a great deal of the winter in a dormant condition, but its body temperature always remains high. Although no one has actually taken a bear's temperature to prove this point (for understandable reasons), there is plenty of indirect evidence. For example, many hunters have reported having found bears curled up on the ground with new fallen snow melted from their backs. Moreover, when disturbed, the bears make off, which would be impossible if the body temperature were near freezing. The most decisive proof is that the she-bear gives birth to her cub in midwinter. How she could give birth and suckle the cub with her body temperature allegedly near freezing has never been explained. Matson (1946) states that it is a scientifically accepted fact that the carnivorous animals (including bears, 'coons, skunks, badgers, etc.), do not hibernate. They do go into deep sleep, but their respiration, rate of heart beat and body temperature are not drastically reduced as they are in hibernation. They are relatively easily aroused from sleep and seem to have full sensibilities and use of their faculties. Although efforts have been made, I do not know of a successful attempt to take the temperature and pulse of a wild dormant bear. The fact that falling snow vanishes from the back of a dormant bear at low temperatures indicates their body temperature does not fall to a great extent. He describes a bear discovered in its hibernating den