Polar bears (Ursus maritimus)

Marine mammals 2013
Typography
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Polar bears have a circumpolar Arctic distribution, which includes the entire northern Barents Sea south to Novaya Zemlya. They are heavily dependent on sea ice for foraging and for travelling to and from terrestrial denning areas; they depend on thick layers of snow in maternity denning areas. They prefer first-year ice that develops over shelf seas for hunting, where ice-associated seals (their primary prey) are most abundant (Derocher et al., 2002). 

Coastal land-fast sea ice is particularly important to mothers with young cubs when they emerge from their dens in the spring (Freitas et al., 2012). Nineteen polar bear populations are currently recognised, varying in size from a few hundred to a few thousand animals; the global population size is ≈26,000 animals (IUCN, 2015). The Barents Sea population, which extends from Svalbard eastwards to Franz Josef Land, is genetically distinct from polar bears in east Greenland and elsewhere. Satellite telemetry has documented routine movements of some bears throughout the entire Barents Sea region (Mauritzen et al., 2002), confirming genetic analyses that suggested there is no geographic distinction between animals from Svalbard and Franz Josef Land (Paetkau et al., 1999; Zeyl et al., 2009; Peacock et al., 2015). Polar bears were exploited in the Barents Region from the late 18th century onward (Uspensky, 1969; Lønø, 1970; Prestrud and Stirling, 1994). Following extreme overexploitation of the stock, hunting was banned in 1956 in Russia and in 1973 in Norway. The first population survey, in 2004, estimated that ~2,650 (95% CI 1,900-3,550) bears reside in the northern Barents Sea (Table 4.2.2, Aars et al., 2009); population trends are currently unknown, but a second survey was flown within Norwegian territory in the northern Barents Sea in 2015, which will provide a new estimate. Population declines are expected in coming decades for most polar bear populations, including that in the Barents Sea because of declining sea ice conditions (e.g. Wiig et al., 2008; Durner et al., 2009; Hunter et al., 2010). In Svalbard, polar bear body condition has not changed over recent decades, nor has the number of cubs-of-the-year per adult female or the number of yearlings per adult female (MOSJ, unpublished data).