Accession Number:

ADA099683

Title:

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

Descriptive Note:

Corporate Author:

ARCTIC INST OF NORTH AMERICA ARLINGTON VA

Report Date:

1978-01-01

Pagination or Media Count:

29.0

Abstract:

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 mlminkg 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 kcalsq mh 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

Subject Categories:

  • Stress Physiology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE