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32nd Annual Arctic Workshop Abstracts
March 14-16, 2002
INSTAAR, University of Colorado at Boulder

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SCOTT, PETER A.. Churchill Northern Studies Centre.

Polar bears spend most of their life on the polar sea ice. At the southern edges of the arctic, populations are found on land during the period when the ice is melting or absent. The western Hudson Bay population has traditionally been without sea ice for approximately 100 days each year during which time the bears fast to conserve energy. Because of the summer fast, the birth and primary development of young polar bears requires at least 8 months of fasting by a female every two or three years. During the 1970s and 1980s the bears of western Hudson Bay were found to be the most productive known and yet they hunted for 100 days less than bears of northern populations did each year. The advantage of food quality or quantity is not justified as the diets are similar, the bears are of similar size, and the bear populations are at similar size and density. This indicates that energy conservation during the maternity period is a critical factor in the productivity of a population. Perhaps one advantage is the noted difference in den selection. While most polar bears den on the sea ice or nearby shore, western Hudson Bay bears den in frozen peat banks found in the riparian habitats south of Churchill, Manitoba, Canada. The author monitored temperature conditions in an assortment of these dens during the fall/winter maternity period. In addition, dens dug in gravel and snow were monitored to examine the differences in temperature. In winter, the peat dens were the same temperature as the surrounding permafrost (-2C) while snow and gravel dens were found to be colder. The past high productivity of the western Hudson Bay population appears to be, in part, because of the use of peat dens as a reproductive strategy.


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