Mercury in the brain of polar bears (Ursus maritimus ) and ringed seals (Pusa hispida).

The paucity of observations of wild polar bears (Ursus maritimus) caching of food (including hoarding, i.e., burying and remaining with a kill for up to a few days) has led to the conclusion that such behavior does not occur or is negligible in this species. We document 19 observations of short-term hoarding by polar bears between 1973 and 2018 in Svalbard, Greenland, and Canada. Short-term hoarding appears to be influenced by size of the kill and its remaining energetic value after the first meal has been consumed. Fat and meat from smaller seals, such as pup or yearling ringed seals (Pusa hispida), are largely devoured immediately, leaving little to hoard. Carcasses of adult ringed seals, harp seals (Pagophilus groenlandicus), and bearded seals (Erignathus barbatus) may be covered with snow to reduce the chance of kleptoparasitism by another bear or other scavengers visually detecting a dark spot on the ice, while the hoarding bear lies nearby. Hoarding of other species, such as beluga (Delphinapterus leucas) (calves or parts) or other polar bears, appears opportunistic. We review differences in caching, including short-term hoarding behavior between polar bears and brown bears (U. arctos), and hypothesize about factors that may have influenced their evolution.

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Relationships between estimates of ringed seal (Phoca hispida) and polar bear (Ursus maritimus) populations in the Canadian Arctic

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f95-849 ◽

1995 ◽

Vol 52 (12) ◽

pp. 2594-2612 ◽

Cited By ~ 107

Author(s):

Ian Stirling ◽

Nils Are Øritsland

Keyword(s):

Metabolic Rate ◽

Population Size ◽

Polar Bear ◽

Population Level ◽

Ursus Maritimus ◽

Polar Bears ◽

Phoca Hispida ◽

Ringed Seals ◽

Reproductive Rates ◽

The Relationship

Analysis of estimates of population size of ringed s,eals (Phoca hispida) and polar bears (Ursus maritimus) from several areas indicated that estimates of one predicted the range of expected population size of the other in areas where ringed seals constitute the primary prey. In some areas, the closeness of this relationship indicates where estimates of either seals or bears may be inaccurate. The number of seals required to support a population of polar bears of predetermined size was estimated independently using both behavioral and energetic data. Behavioral estimates of the number of seals killed may overestimate energetic requirements and vice versa. Predation and energy matrices indicated that high levels of predation on seals are sustainable only if most animals killed are young-of-the-year. The field metabolic rate of the polar bear appears to be about twice the basal metabolic rate. Densities of seals vary in response to overall productivity of the ecosystem in different areas, and fluctuations in their numbers and reproductive rates between years can be used to monitor changes in productivity of the ecosystem. These changes also cause variation in productivity of bears, which indicates the sensitivity, at the population level, of the relationship between ringed seals and polar bears.

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Midsummer observations on the behavior of wild polar bears (Ursus maritimus)

Canadian Journal of Zoology ◽

10.1139/z74-157 ◽

1974 ◽

Vol 52 (9) ◽

pp. 1191-1198 ◽

Cited By ~ 100

Author(s):

Ian Stirling

Keyword(s):

Diurnal Rhythm ◽

Intraspecific Competition ◽

Ursus Maritimus ◽

Polar Bears ◽

Phoca Hispida ◽

Devon Island ◽

Adult Females ◽

Ringed Seals ◽

Single Animal ◽

The Mean

Wild polar bears (Ursus maritimus) were observed from Caswall Tower, Devon Island (74°43′ N; 91°10′ W), from 24 July to 8 August 1973. A total of 602.7 bear hours of observations was recorded. Two types of hunting were observed, stalking and still-hunting. Of 288 hunts observed, 65 (22.6%) were stalks and 233 (77.4%) were still-hunts. All cubs observed hunted, but they exhibited great variety in patience and apparent skill. Scavenging and intraspecific competition for possession of kills were observed. When threatened, adult females with cubs were not subordinate to tears of any other age or sex classes. A diurnal rhythm was recorded in which bears slept most during the latter third of the 24-h cycle and least in the first third. The average of 17 sleeps longer than 60 min was 465 ± 301.3 min.Basking ringed seals (Phoca hispida) alternated between lying flat and raising their heads to look about for predators. The mean duration of the lying and looking phases was 26.3 and 7.0 s respectively (n = 591 and 580). The variation between individual seals was greater than within individuals. If a group of seals hauled out together, all individuals maintained watchful behavior; no single animal acted as a "sentry" for the others.

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The influence of climate variability on polar bear (Ursus maritimus) and ringed seal (Pusa hispida) population dynamics

Canadian Journal of Zoology ◽

10.1139/z06-001 ◽

2006 ◽

Vol 84 (3) ◽

pp. 357-364 ◽

Cited By ~ 10

Author(s):

A Rosing-Asvid

Keyword(s):

Polar Bear ◽

Ursus Maritimus ◽

Early Spring ◽

Ringed Seal ◽

Polar Bears ◽

Lactation Period ◽

Long Time ◽

Pusa Hispida ◽

By Catch ◽

Catch Statistics

Unusually high polar bear (Ursus maritimus Phipps, 1774) predation on ringed seal (Pusa hispida (Schreber, 1775)) pups and increased survival of polar bear cubs during mild springs is documented in published articles. Strong predation on newborn ringed seal pups in early spring, however, is likely to lower the overall energy intake of polar bears if ringed seal pups are their main food, because the energetic value of ringed seal pups increases 7–8 times during the 6 week lactation period. So although hunting success in early spring increases cub survival during the period after den emergence,when they are most vulnerable, it is likely to increase the number of starving bears later in the season. This negative-feedback effect of strong spring predation will not occur in areas where other seal species are abundant during summer, and polar bears in such areas are likely to exhibit population growth during periods with milder springs, at least until the ringed seal population has been depleted. Long time series of population estimates that can be used to test this hypothesis do not exist, but it is strongly supported by catch statistics for polar bears and ringed seals from east Greenland.

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Aspects of Predation of Seals by Polar Bears

Journal of the Fisheries Research Board of Canada ◽

10.1139/f77-169 ◽

1977 ◽

Vol 34 (8) ◽

pp. 1126-1129 ◽

Cited By ~ 156

Author(s):

Ian Stirling ◽

W. Ralph Archibald

Keyword(s):

High Arctic ◽

Ursus Maritimus ◽

Polar Bears ◽

Phoca Hispida ◽

Ringed Seals ◽

Arctic Foxes ◽

Large Numbers ◽

Erignathus Barbatus ◽

Western Arctic ◽

Bearded Seals

Data were collected from 227 ringed seals (Phoca hispida) and bearded seals (Erignathus barbatus) killed by polar bears (Ursus maritimus) in the western arctic and the eastern high arctic. During periods of high ringed seal productivity, pups constituted at least half of the seals killed in both areas during the spring. Bearded seals were taken less often than ringed seals in both areas but were more important as prey to polar bears in the western arctic. Carcass utilization was significantly higher in the eastern high arctic than in the western arctic although the reason was not apparent. Scavenging of unutilized seal remains is probably of great importance to the survival of large numbers of arctic foxes (Alopex lagopus) through the winter. Key words: Ursus maritimus, Phoca hispida, Erignathus barbatus, predation, interspecific relationships, Arctic Ocean mammals

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