Observations of Cannibalism by Polar Bears (Ursus maritimus) on Summer and Autumn Sea Ice at Svalbard, Norway

ARCTIC ◽  
2011 ◽  
Vol 64 (4) ◽  
Author(s):  
Ian Stirling ◽  
Jenny E. Ross
Keyword(s):  
Sea Ice ◽  
Ursus Maritimus ◽  
Polar Bears

scholarly journals Long-distance swimming by polar bears (Ursus maritimus) of the southern Beaufort Sea during years of extensive open water

2012 ◽  
Vol 90 (5) ◽  
pp. 663-676 ◽  
Author(s):  
A.M. Pagano ◽  
G.M. Durner ◽  
S.C. Amstrup ◽  
K.S. Simac ◽  
G.S. York
Keyword(s):  
Sea Ice ◽  
Adult Female ◽  
Open Water ◽  
Ursus Maritimus ◽  
Polar Bears ◽  
Long Distance ◽  
Gps Collars ◽  
Movement Data ◽  
Global Positioning ◽  
Ice Conditions

Polar bears ( Ursus maritimus Phipps, 1774) depend on sea ice for catching marine mammal prey. Recent sea-ice declines have been linked to reductions in body condition, survival, and population size. Reduced foraging opportunity is hypothesized to be the primary cause of sea-ice-linked declines, but the costs of travel through a deteriorated sea-ice environment also may be a factor. We used movement data from 52 adult female polar bears wearing Global Positioning System (GPS) collars, including some with dependent young, to document long-distance swimming (>50 km) by polar bears in the southern Beaufort and Chukchi seas. During 6 years (2004–2009), we identified 50 long-distance swims by 20 bears. Swim duration and distance ranged from 0.7 to 9.7 days (mean = 3.4 days) and 53.7 to 687.1 km (mean = 154.2 km), respectively. Frequency of swimming appeared to increase over the course of the study. We show that adult female polar bears and their cubs are capable of swimming long distances during periods when extensive areas of open water are present. However, long-distance swimming appears to have higher energetic demands than moving over sea ice. Our observations suggest long-distance swimming is a behavioral response to declining summer sea-ice conditions.

scholarly journals Testing the hypothesis that routine sea ice coverage of 3-5 mkm2 results in a greater than 30% decline in population size of polar bears (Ursus maritimus)

2017 ◽  
Author(s):  
Susan J Crockford
Keyword(s):  
Sea Ice ◽  
Population Size ◽  
Habitat Loss ◽  
Polar Bear ◽  
Population Decline ◽  
Ursus Maritimus ◽  
The Arctic ◽  
Polar Bears ◽  
Population Declines ◽  
Sea Ice Decline

The polar bear (Ursus maritimus) was the first species to be classified as threatened with extinction based on predictions of future conditions rather than current status. These predictions were made using expert-opinion forecasts of population declines linked to modeled habitat loss – first by the International Union for the Conservation of Nature (IUCN)’s Red List in 2006, and then by the United States Fish and Wildlife Service (USFWS) in 2008 under the Endangered Species Act (ESA), based on data collected to 2005 and 2006, respectively. Both assessments predicted significant population declines of polar bears would result by mid-century as a consequence of summer sea ice extent rapidly reaching 3-5 mkm2 on a regular basis: the IUCN predicted a >30% decline in total population, while the USFWS predicted the global population would decline by 67% (including total extirpation of ten subpopulations within two vulnerable ecoregions). Biologists involved in these conservation assessments had to make several critical assumptions about how polar bears might be affected by future habitat loss, since sea ice conditions predicted to occur by 2050 had not occurred prior to 2006. However, summer sea ice declines have been much faster than expected: low ice levels not expected until mid-century (about 3-5 mkm2) have occurred regularly since 2007. Realization of predicted sea ice levels allows the ‘rapid sea ice decline = population decline’ assumption for polar bears to be treated as a testable hypothesis. Data collected between 2007 and 2015 reveal that polar bear numbers have not declined as predicted and no subpopulation has been extirpated. Several subpopulations expected to be at high risk of decline remained stable and five showed increases in population size. Another at-risk subpopulation was not counted but showed marked improvement in reproductive parameters and body condition with less summer ice. As a consequence, the hypothesis that repeated summer sea ice levels of below 5 mkm2 will cause significant population declines in polar bears is rejected, a result that indicates the ESA and IUCN judgments to list polar bears as threatened based on future risks of habitat loss were scientifically unfounded and that similar predictions for Arctic seals and walrus may be likewise flawed. The lack of a demonstrable ‘rapid sea ice decline = population decline’ relationship for polar bears also potentially invalidates updated survival model outputs that predict catastrophic population declines should the Arctic become ice-free in summer.

scholarly journals Testing the hypothesis that routine sea ice coverage of 3-5 mkm2 results in a greater than 30% decline in population size of polar bears (Ursus maritimus)

2017 ◽  
Author(s):  
Susan J Crockford
Keyword(s):  
Sea Ice ◽  
Population Size ◽  
Habitat Loss ◽  
Polar Bear ◽  
Population Decline ◽  
Ursus Maritimus ◽  
The Arctic ◽  
Polar Bears ◽  
Population Declines ◽  
Sea Ice Decline

The polar bear (Ursus maritimus) was the first species to be classified as threatened with extinction based on predictions of future conditions rather than current status. These predictions were made using expert-opinion forecasts of population declines linked to modeled habitat loss – first by the International Union for the Conservation of Nature (IUCN)’s Red List in 2006, and then by the United States Fish and Wildlife Service (USFWS) in 2008 under the Endangered Species Act (ESA), based on data collected to 2005 and 2006, respectively. Both assessments predicted significant population declines of polar bears would result by mid-century as a consequence of summer sea ice extent rapidly reaching 3-5 mkm2 on a regular basis: the IUCN predicted a >30% decline in total population, while the USFWS predicted the global population would decline by 67% (including total extirpation of ten subpopulations within two vulnerable ecoregions). Biologists involved in these conservation assessments had to make several critical assumptions about how polar bears might be affected by future habitat loss, since sea ice conditions predicted to occur by 2050 had not occurred prior to 2006. However, summer sea ice declines have been much faster than expected: low ice levels not expected until mid-century (about 3-5 mkm2) have occurred regularly since 2007. Realization of predicted sea ice levels allows the ‘rapid sea ice decline = population decline’ assumption for polar bears to be treated as a testable hypothesis. Data collected between 2007 and 2015 reveal that polar bear numbers have not declined as predicted and no subpopulation has been extirpated. Several subpopulations expected to be at high risk of decline remained stable and five showed increases in population size. Another at-risk subpopulation was not counted but showed marked improvement in reproductive parameters and body condition with less summer ice. As a consequence, the hypothesis that repeated summer sea ice levels of below 5 mkm2 will cause significant population declines in polar bears is rejected, a result that indicates the ESA and IUCN judgments to list polar bears as threatened based on future risks of habitat loss were scientifically unfounded and that similar predictions for Arctic seals and walrus may be likewise flawed. The lack of a demonstrable ‘rapid sea ice decline = population decline’ relationship for polar bears also potentially invalidates updated survival model outputs that predict catastrophic population declines should the Arctic become ice-free in summer.

Sea ice-associated decline in body condition leads to increased concentrations of lipophilic pollutants in polar bears ( Ursus maritimus ) from Svalbard, Norway

2017 ◽  
Vol 576 ◽  
pp. 409-419 ◽  
Author(s):  
Sabrina Tartu ◽  
Sophie Bourgeon ◽  
Jon Aars ◽  
Magnus Andersen ◽  
Anuschka Polder ◽  
...  
Keyword(s):  
Sea Ice ◽  
Body Condition ◽  
Ursus Maritimus ◽  
Polar Bears

scholarly journals Changes in winter and spring resource selection by polar bears Ursus maritimus in Baffin Bay over two decades of sea-ice loss

2018 ◽  
Vol 36 ◽  
pp. 1-14 ◽  
Author(s):  
KL Laidre ◽  
H Stern ◽  
EW Born ◽  
P Heagerty ◽  
S Atkinson ◽  
...  
Keyword(s):  
Sea Ice ◽  
Resource Selection ◽  
Ursus Maritimus ◽  
Polar Bears ◽  
Baffin Bay

scholarly journals Predation of Harp Seals, Pagophilus groenlandicus, by Polar Bears, Ursus maritimus, in Svalbard

ARCTIC ◽  
2019 ◽  
Vol 72 (2) ◽  
pp. 197-202 ◽  
Author(s):  
Thomas G. Smith ◽  
Ian Stirling
Keyword(s):  
Sea Ice ◽  
Polar Bear ◽  
Barents Sea ◽  
Population Level ◽  
Open Water ◽  
Ursus Maritimus ◽  
Polar Bears ◽  
Pagophilus Groenlandicus ◽  
Large Numbers ◽  
Pack Ice

Harp seals (Pagophilus groenlandicus) that breed in February and March in the White Sea migrate to open water around Svalbard and Franz Josef Land in the Barents Sea, feeding pelagically while following the receding ice edge northward to the edge of the polar pack. Although harp seals are present throughout the area during the summer, they are primarily pelagic and do not appear to be extensively preyed upon by polar bears (Ursus maritimus). However, occasionally, large numbers of harp seals may haul out and rest on the pack ice or feed in the water below the ice and surface to breathe between the floes. When approached by a polar bear while on the ice, harp seals do not exhibit the instant flight response characteristic of the polar bear’s primary prey species, ringed (Pusa hispida) and bearded seals (Erignathus barbatus). In this situation, polar bears may make multiple kills without either consuming their own prey or scavenging seals killed by other bears. This behavior appears not to frighten other nearby harp seals, whether hauled out on the ice or in the water below the floes. These unusual concentrations of harp seals hauled out on sea ice may be related to the distribution and abundance of fish or other epontic prey. Their lack of an escape response to predators on the surface of the sea ice is probably a result of briefly hauling out in large numbers in spring while whelping on the sea ice in areas where the consequences of potential polar bear predation are insignificant. The rare events of harp seal mortality from bears killing them on the surface of pack ice during the summer do not appear to have a significant impact at the population level of either species.

Spatial relationships and behavior of polar bears (Ursus maritimus Phipps) concentrated on land during the ice-free season of Hudson Bay

1981 ◽  
Vol 59 (9) ◽  
pp. 1763-1774 ◽  
Author(s):  
Paul B. Latour
Keyword(s):  
Social Behavior ◽  
Sea Ice ◽  
Social Systems ◽  
Ursus Maritimus ◽  
Hudson Bay ◽  
Polar Bears ◽  
Adult Males ◽  
Single Population ◽  
A Site ◽  
And Behavior

I observed polar bears (Ursus maritimus Phipps) at Cape Churchill, Manitoba, a site where polar bears congregate during the autumn when Hudson Bay is ice free. Adult males, subadult males, and subadult females were spatially segregated to a degree that depended primarily on density. The higher the density, the greater the degree of segregation. Adult males showed the closest intraclass association. Subadult females spent more time in activity than did either adult or subadult males; this may be due to subadult females being approached more by other subadults. Much of an individual's social behavior occurred with members of its own age–sex class, perhaps as a result of spatial segregation. In the noncompetitive situation of this study, polar bears aggregated and were more social than when hunting on the sea ice. This study provides further evidence for the flexibility of carnivore social systems, not only between populations of the same species, but also within a single population.

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