The number and distribution of polar bears in the western Barents Sea

Abstract

Polar bears have experienced a rapid loss of sea-ice habitat in the Barents Sea. Monitoring this subpopulation focuses on the effects on polar bear demography. In August 2015, we conducted a survey in the Norwegian Arctic to estimate polar bear numbers and reveal population substructure. DNA profiles from biopsy samples and ear tags identified on photographs revealed that about half of the bears in Svalbard, compared to only 4.5% in the pack ice north of the archipelago, were recognized recaptures. The recaptured bears had originally been marked in Svalbard, mostly in spring. The existence of a local Svalbard stock, and another ecotype of bears using the pack ice in autumn with low likelihood of visiting Svalbard, support separate population size estimation for the two areas. Mainly by aerial survey line transect distance sampling methods, we estimated that 264 (95% CI = 199-363) bears were in Svalbard, close to 241 bears estimated for August 2004. The pack ice area had an estimated 709 bears (95% CI = 334-1026). The pack ice and the total (Svalbard + pack ice, 973 bears, 95% CI = 334-1026) both had higher estimates compared to August 2004 (444 and 685 bears, respectively), but the increase was not significant. There is no evidence that the fast reduction of sea-ice habitat in the area has yet led to a reduction in population size. The carrying capacity is likely reduced significantly, but recovery from earlier depletion up to 1973 may still be ongoing.

Aquatic behaviour of polar bears (Ursus maritimus) in an increasingly ice-free Arctic

“…Coastal space use was overrepresented in this study: two-thirds of the polar bears were considered to belong to the local ecotype, while this group as a whole constitutes maybe only a tenth of the subpopulation 17 , 29 . While the analysis indicated broadly similar patterns in the amount and timing of swimming performed by local polar bears and offshore polar bears, differences may have been masked by the large individual variation in aquatic behaviour and relatively small sample for polar bears using the offshore strategy.…”

“…Monthly time in water was compared for the two main behavioural strategies that exist in the subpopulation 16 , 17 . Whether polar bears stay coastal or go offshore was classified by visual inspection of the tracking data.…”

Environmental contaminants modulate the transcriptional activity of polar bear (Ursus maritimus) and human peroxisome proliferator-activated receptor alpha (PPARA)

“…PFNA-mediated changes in PPARA functions are likely to increase in the future, as PFNA concentrations have increased 2.5% per year in Barents Sea polar bears during the period 2000–2014, whereas PFOS concentrations have been stable since 2009 72 . Furthermore, with the declining sea ice the Barents Sea, there is an increase in the use of offshore areas at the eastern Barents Sea by polar bears 73 , and bears using these areas have higher PFAS concentrations than those which stay close to the Svalbard Archipelago 74 .…”

Predation of Harp Seals, <i>Pagophilus groenlandicus</i>, by Polar Bears, <i>Ursus maritimus</i>, in Svalbard

“…Additionally, where other species of marine mammals are present and there are opportunities to prey or scavenge upon them, polar bears have also been recorded feeding on species as diverse as harp seals (Pagophilus groenlandicus), hooded seals (Cystophora cristata), beluga whales (Delphinapterus leucas), narwhals (Monodon monoceros), harbor seals (Phoca vitulina), walrus (Odobenus rosmarus), and bowhead whales (Balaena mysticetus) (Thiemann et al, 2008). However, as climate warming continues to have negative effects on sea ice throughout the circumpolar Arctic (Regehr et al, 2016) and the fast ice pupping habitat of ringed seals in particular (e.g., Stirling and Smith, 2004), the nutritional importance of species such as harp seals to small numbers of polar bears in the northern pack ice areas (Aars et al, 2017) may increase, even if only for brief periods during the summer.…”