Modes of Thermal Protection in Polar Bear Cubs - at Birth and upon Emergence from the Den

• Main Authors: Blix,Arnoldus Schytte, Lentfer,Jack W
• Other Authors: ARCTIC INST OF NORTH AMERICA ARLINGTON VA
• Format: Text
• Language: English
• Published: 1978
• Subjects: Stress Physiology; *METABOLISM; *TOLERANCES(PHYSIOLOGY); *HEAT PRODUCTION(BIOLOGY); LOW TEMPERATURE; ALASKA; RATES; PROTECTION; HEAT; THERMAL INSULATION; BODY TEMPERATURE; FUR; Polar bears; Anchorage; Arctic; Fairbanks; Barrow; Point Barrow; Alaska
• Online Access: http://www.dtic.mil/docs/citations/ADA099683; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA099683

At birth in late December the polar bear is small (700 g), uninsulated and helpless. It probably has a modest capacity for metabolic heat production and depends on the female and a snow den in which it is born for thermal protection. The microclimate of an artificial polar bear den was investigated at Point Barrow, Alaska, and the temperature therein found to stay around 0 C provided a heat source (200 W) equivalent to an adult polar bear was introduced. When the bears desert the den in early April the cub has grown to about 10 kg and has a well developed fur insulation, but almost no subcutaneous fat. The cub has a high resting metabolic rate (14.2 ml/min/kg) which is supported by the fat polar bear milk. Its lower critical temperature is about -30 C, and an ambient temperature of -45 C results in only a 33% increase in metabolism. The cub can tolerate a windchill of 2000 kcal/sq m/h without apparent stress or drop in rectal temperature. If the cub is immersed in ice-water rectal temperature drops 11 C in 30 min. It is concluded that the cub can tolerate extremely low temperatures in air due to fur insulation and high metabolic heat production, but is unable to cope with the chill of ice-water for any prolonged period of time. (Author) Prepared in cooperation Alaska Univ., Fairbanks. Inst. of Marine Science and Arctic Biology and U.S. National Fish and Wildlife Lab., Anchorage, AK.