The meeting of two dynamics : polar bears and sea ice

A geological event, the freezing of the Arctic ocean, resulted in speciation and the evolution of polar bears. The sea-ice landscape now maintains this diversity. Thus the past and present dynamics of sea ice are inextricably linked with the dynamics of polar bears. First, I investigated patterns of space use for polar bears of Baffin Bay during the ice-free period. Females with cubs-of-the-year were first to leave the ice for land and they rarely used snow shelters. In contrast, pregnant females were the last to leave the ice for land, and after about 1 week on land, they entered a maternal den for the winter. Most females with 1-year-olds entered a shelter after about 3 weeks on land and remained there for about 2 months. During the ice-free period, females with cubs-of-the-year were farther inland, closer to fjords, and less likely to use islands than males. Spatially, polar bears grouped into clusters that matched the fractal pattern of seasonal sea ice interspersed among arctic islands. The winter and spring seasons, before and during mating, respectively, best described groupings of polar bears based on separate analyses of ice and bears. A relationship between polar bear fractal movement patterns and the fractal dimension of sea ice indicated a possible mechanism linking geography and population structure. Last, I looked at polar bears on a temporal scale to understand how the cycles of sea ice affected the seasonal patterns of polar bears. As the location and accessibility of seals to bears depends on characteristics of ice, I used radio telemetry and satellite imageries to describe seasonal patterns of ice selection by female polar bears for two Canadian Arctic regions. Whereas the Arctic Archipelago remained mostly ice covered throughout the year, Baffin Bay cycled seasonally from 100% ice in winter to