Physiological Condition of Three Species of Bears in Winter Dens

Abstract

SUMMARY The concepts of this paper include: A. Winter dormancy of the black and grizzly bear is characterized by a slow heart beat or bradycardia more prolonged than that found during the dive of marine mammals. B. This dormancy of the black and the grizzly bear seems fairly complete with few of these two species active in midwinter. During this period of dor? mancy, for nearly six months in Alaska, these animals do not urinate, defecate, eat or drink. In a sense their dormancy is more complete than that found in the typical mammalian hibernator which reduces his body temperature and metabolism, but awakens sporadically every four to ten days and may, then, drink, eat, urinate or defecate. C. Two male polar bears demonstrated that they too have the capacity to re? duce physiological functions in midwinter. This was much harder to prove in these animals than in the other two species. Evidence is cited that many polar bears cannot prepare for this period of dormancy by laying down subcutaneous fat. This probably prevents them from taking on this state of dormancy, al? though it is quite possible that at least for a month at a time even on the Polar Ice Pack, bears may make use of their ability to reduce heart rate and perhaps body temperature and metabolism. D. The test of the configuration of the EKG pattern has been applied to three species of bears; this pattern appears to be more like that of mammalian hibernators than like'that of other types of mammals.