Abstract 159 – Sea Ice Phenology and Polar Bear Habitat Selection at the Southern Extent of the Species’ Range

Tyler Ross, Gregory W. Thiemann, Martyn E. Obbard, Kevin R. Middel, Joseph M.
Northrup

Accounting for differences in habitat use among individuals within sympatric populations is
important for identifying appropriate scales of management, particularly in the context of
climate change, which may differentially impact wildlife based on their spatial distribution. This
is especially relevant in the Arctic where temperatures are warming faster than the global
average. For sea-ice-dependent species such as polar bears (Ursus maritimus), understanding
regional differences in habitat use is essential for crafting adaptive conservation strategies that
reflect the different scales at which climate change may be affecting the species across its
range. Here, we examined long-term trends in sea ice phenology, and habitat selection of polar
bears in James Bay, the southern-most continuously occupied area of the species’ range.
Between 1979-2022, duration of the ice-free season increased at a rate of 2.9 days decade-1,
slower than the broader Southern Hudson Bay area, which experienced an increase of 4.7 days
decade-1 over the same period. Polar bears equipped with GPS-satellite collars between 2012-
2015 varied in the extent of their geographic home ranges, ranging from 23,596-263,679 km2.
The population-level home range encompassed 121,338 km2, and included areas extending
from the Belcher Islands to southern James Bay. Polar bears exhibited seasonal variation in
selection of finer-scale habitat characteristics within their home range. Bears routinely selected
areas with higher sea ice concentration, and appeared to prefer areas further from the coast
during the early winter, then switched to areas closer to shore during spring when prey
availability peaks. Documenting sea ice conditions and patterns of polar bear habitat selection
is important to establish baseline information against which future changes can be compared.
This is particularly important for polar bears at the southern extent of their range where near-
term changes are expected to be greatest.