Habitat Selection and Intrapopulation Spatial Segregation in an Arctic Top Predator at the Southern Limit of Its Range.

Accounting for spatial structure within populations is critical for defining appropriate scales of management, particularly in the Arctic, where habitats of ice-dependent species such as the polar bear (Ursus maritimus) are being transformed at an accelerated rate. We examined broad-scale patterns of space use and finer-scale habitat selection by adult female polar bears in James Bay, located at the southernmost extent of the species' global range. Using satellite telemetry data collected during the annual on-ice period from 2012 to 2017, we estimated individual- and population-level utilization distributions (UDs) and applied hierarchical clustering to assess whether individuals formed distinct spatial groups based on the degree of UD overlap. We also fit step-selection functions (SSFs) to evaluate selection for sea-ice concentration, ocean depth, and distance to coast. Fifteen bears with data spanning at least one complete on-ice period had individual 95% UDs averaging 74,770 km2 (SE = 11,663). Results of hierarchical clustering identified two distinct spatial groups: three "resident" bears remained within southern James Bay, whereas 12 "non-resident" bears had larger UDs extending into Hudson Bay. Overlap between groups remained near zero throughout winter, including during the breeding season. Step-selection analyses, which included an additional four bears (ntotal = 19), indicated consistent positive selection for high sea-ice concentration, with individual variation in selection strength. For non-resident bears, selection for distance to coast and ocean depth varied seasonally, with bears selecting areas farther from the Ontario coast during freeze-up, closer to the coast during April-May, and deeper offshore areas during breakup. Together with previous genetic evidence, our results suggest resident southern James Bay bears represent a spatially structured component of the broader subpopulation that warrants continued monitoring and explicit consideration in future harvest-risk assessments and conservation planning, particularly as sea-ice loss continues to alter habitat availability.