Data from: Range contraction and increasing isolation of a polar bear subpopulation in an era of sea-ice loss

Climate change is expected to result in range shifts and habitat
fragmentation for many species. In the Arctic, loss of sea ice will reduce
barriers to dispersal or eliminate movement corridors, resulting in
increased connectivity or geographic isolation with sweeping implications
for conservation. We used satellite telemetry, data from individually
marked animals (research and harvest), and microsatellite genetic data to
examine changes in geographic range, emigration, and interpopulation
connectivity of the Baffin Bay (BB) polar bear (Ursus maritimus)
subpopulation over a 25-year period of sea-ice loss. Satellite telemetry
collected from n = 43 (1991–1995) and 38 (2009–2015) adult females
revealed a significant contraction in subpopulation range size (95%
bivariate normal kernel range) in most months and seasons, with the most
marked reduction being a 70% decline in summer from 716,000 km2 (SE
58,000) to 211,000 km2 (SE 23,000) (p < .001). Between the 1990s
and 2000s, there was a significant shift northward during the on-ice
seasons (2.6° shift in winter median latitude, 1.1° shift in spring median
latitude) and a significant range contraction in the ice-free summers.
Bears in the 2000s were less likely to leave BB, with significant
reductions in the numbers of bears moving into Davis Strait (DS) in winter
and Lancaster Sound (LS) in summer. Harvest recoveries suggested both
short and long-term fidelity to BB remained high over both periods (83–99%
of marked bears remained in BB). Genetic analyses using eight polymorphic
microsatellites confirmed a previously documented differentiation between
BB, DS, and LS; yet weakly differentiated BB from Kane Basin (KB) for the
first time. Our results provide the first multiple lines of evidence for
an increasingly geographically and functionally isolated subpopulation of
polar bears in the context of long-term sea-ice loss. This may be
indicative of future patterns for other polar bear subpopulations under
climate change.