Terrestrial Maternity Denning of Polar Bears in the Eastern Beaufort Sea Area

Observations on the location of polar bear (Ursus maritimus) maternity dens, the locations of females with young cubs on the sea ice just after leaving their dens, and observations of Inuvialuit hunters were recorded in the eastern Beaufort Sea area from late March to mid-May 1971-79 and 1985-87. Maternity denning occurs annually on the west and south coasts of Banks Island but it has been recorded less frequently along the mainland coast of the southern Beaufort Sea. This distribution pattern could have been influenced by the pattern of sea ice formation in the fall and anthropogenic factors. Denning females and females accompanied by young cubs have been protected for almost 20 years, and maternity denning along the mainland coast appears to be increasing as a result.Key words: polar bear, denning, Beaufort Sea, Banks IslandRÉSUMÉ. Des observations faites sur l’emplacement des tanières de mise bas d’ourses polaires (Ursus maritimus), l’emplacement des femelles avec leurs oursons sur la banquise juste après l’abandon de la tanière ainsi que des observations faites par des chasseurs Inuvialuit ont été enregistrées dans la mer de Beaufort de la fin mars à la mi-mai de 1971à 1979 et de 1985 à 1987. La mise bas dans les tanières à eu lieu chaque année sur la côte occidentale et méridionale de l’île Banks mais on l’a rapportée moins fréquemment le long du rivage continental du sud de la mer de Beaufort. Il se peut que ce schéma de distribution ait été influencé par le schéma de formation de la banquise à l’automne et par des facteurs anthropiques. Les femelles qui mettent bas et celles accompagnées de leur oursons sont protégées depuis au moins 20 ans, ce qui semblerait résulter en une augmentation de la mise bas dans des tanières le long du rivage continental.Mots clés: ours polaire, tanière de mise bas, mer de Beaufort, île Bank

Terrestrial Foraging by Polar Bears during the Ice-Free Period in Western Hudson Bay

Food habits of polar bears on land during the ice-free period in western Hudson Bay were examined between 1986 and 1992. In contrast to previous studies, feeding on vegetation during the ice-free period was common. Between August and October, evidence of feeding was found in 34% of the females and 26% of the males captured over 10 km inland from the coast. The primary forage was Vaccinium uliginosum and Empetrum nigrum berries. Feeding was most common in subadults and females. The incidence of feeding on berries varied annually from 2 to 41%. We were not able to determine the energetic importance of terrestrial foraging, but the intake may reduce the rate of weight loss of bears on land, particularly in years when berries are abundant.Key words: polar bears, Ursus maritimus, feeding, arctic food webOn a étudié les habitudes alimentaires des ours polaires à terre durant la période libre de glace dans l'ouest de la baie d'Hudson entre 1986 et 1992. Contrairement aux études antérieures, l'alimentation végétale durant la période libre de glace était commune. Entre août et octobre, on a pu documenter l'alimentation chez 34 p. cent des femelles et 26 p. cent des mâles capturés dans une zone s'étendant jusqu'à 10 km à l'intérieur des terres. Le fourrage principal était constitué des baies Vaccinium uliginosum et Empetrum nigrum. La nourriture était surtout consommée par les jeunes adultes et les femelles. L'incidence de l'alimentation constituée de baies variait annuellement de 2 à 41 p. cent. On n'a pas été en mesure de déterminer l'importance énergétique de l'alimentation végétale terrestre, mais son absorption pourrait réduire le taux de perte de poids des ours à terre, en particulier les années où il y a une abondance de baies.Mots clés : ours polaires, Ursus maritirnus, alimentation, réseau trophique arctiqu

What are the toxicological effects of mercury in Arctic biota?

This review critically evaluates the available mercury (Hg) data in Arctic marine biota and the Inuit population against toxicity threshold values. In particular marine top predators exhibit concentrations of mercury in their tissues and organs that are believed to exceed thresholds for biological effects. Species whose concentrations exceed threshold values include the polar bears (Ursus maritimus), beluga whale (Delphinapterus leucas), pilot whale (Globicephala melas), hooded seal (Cystophora cristata), a few seabird species, and landlocked Arctic char (Salvelinus alpinus). Toothed whales appear to be one of the most vulnerable groups, with high concentrations of mercury recorded in brain tissue with associated signs of neurochemical effects. Evidence of increasing concentrations in mercury in some biota in Arctic Canada and Greenland is therefore a concern with respect to ecosystem health

Age and sex composition of seals killed by polar bears in the eastern Beaufort Sea.

Polar bears (Ursus maritimus) of the Beaufort Sea enter hyperphagia in spring and gain fat reserves to survive periods of low prey availability. We collected information on seals killed by polar bears (n=650) and hunting attempts on ringed seal (Pusa hispida) lairs (n=1396) observed from a helicopter during polar bear mark-recapture studies in the eastern Beaufort Sea in spring in 1985-2011. We investigated how temporal shifts in ringed seal reproduction affect kill composition and the intraspecific vulnerabilities of ringed seals to polar bear predation.Polar bears primarily preyed on ringed seals (90.2%) while bearded seals (Erignathus barbatus) only comprised 9.8% of the kills, but 33% of the biomass. Adults comprised 43.6% (150/344) of the ringed seals killed, while their pups comprised 38.4% (132/344). Juvenile ringed seals were killed at the lowest proportion, comprising 18.0% (62/344) of the ringed seal kills. The proportion of ringed seal pups was highest between 2007-2011, in association with high ringed seal productivity. Half of the adult ringed seal kills were ≥ 21 years (60/121), and kill rates of adults increased following the peak of parturition. Determination of sex from DNA revealed that polar bears killed adult male and adult female ringed seals equally (0.50, n=78). The number of hunting attempts at ringed seal subnivean lair sites was positively correlated with the number of pup kills (r(2) =0.30, P=0.04), but was not correlated with the number of adult kills (P=0.37).Results are consistent with decadal trends in ringed seal productivity, with low numbers of pups killed by polar bears in spring in years of low pup productivity, and conversely when pup productivity was high. Vulnerability of adult ringed seals to predation increased in relation to reproductive activities and age, but not gender

Relationship between attempted hunts on subnivean ringed seal lairs (digs) observed per flight day and ringed seal kills.

<p>5a: pups (0+ years, <i>r²</i> = 0.30, <i>P</i> = 0.04). 5b: adults (≥7 years, <i>P</i> = 0.37). Observations were pooled (<i>n = </i>14) into early (▴, ≤ April 25) and late season (▪, ≥ April 26). Data shown untransformed; see text.</p

Mean daily number of kills observed per five-day period in the eastern Beaufort Sea between 1985–2011.

<p>4a: Mean daily number of all kills observed (± SE); error represents combined daily and annual variation in observations. Grey shading indicates peak ringed seal whelping in the Beaufort Sea <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041429#pone.0041429-Smith1" target="_blank">[12]</a>. 4b: Mean number of ringed seal pup (0+ years), juvenile (1–6 years) and adult (≥7 years) kills observed.</p

Proportions of ringed seals killed by polar bears in the eastern Beaufort Sea between 1971–2011, categorized by pup (0+ years), juvenile (1–6 years) and adult (≥7 years) age classes (95% CI shown).

<p>Data from 1971–1975 reproduced with permission from Stirling and Archibald <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041429#pone.0041429-Stirling2" target="_blank">[11]</a>. *Years with lower ringed seal reproduction as recorded at Sachs Harbour and Ulukhaktok <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041429#pone.0041429-Kingsley1" target="_blank">[24]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041429#pone.0041429-Harwood1" target="_blank">[25]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041429#pone.0041429-Harwood2" target="_blank">[63]</a>.</p

What are the toxicological effects of mercury in Arctic biota?

This review critically evaluates the available mercury (Hg) data in Arctic marine biota and the Inuit population against toxicity threshold values. In particular marine top predators exhibit concentrations of mercury in their tissues and organs that are believed to exceed thresholds for biological effects. Species whose concentrations exceed threshold values include the polar bears (Ursus maritimus), beluga whale (Delphinapterus leucas), pilot whale (Globicephala melas), hooded seal (Cystophora cristata), a few seabird species, and landlocked Arctic char (Salvelinus alpinus). Toothed whales appear to be one of the most vulnerable groups, with high concentrations of mercury recorded in brain tissue with associated signs of neurochemical effects. Evidence of increasing concentrations in mercury in some biota in Arctic Canada and Greenland is therefore a concern with respect to ecosystem health