Seasonal and annual movement patterns of polar bears on the sea ice of Hudson Bay

2006 ◽  
Vol 84 (9) ◽  
pp. 1281-1294 ◽  
Author(s):  
E.K. Parks ◽  
A.E. Derocher ◽  
N.J. Lunn
Keyword(s):  
Sea Ice ◽  
Polar Bear ◽  
Movement Patterns ◽  
Temporal Changes ◽  
Reproductive Status ◽  
Energy Output ◽  
Hudson Bay ◽  
Polar Bears ◽  
Western Hudson Bay ◽  
Break Up

Polar bears ( Ursus maritimus Phipps, 1774) move thousands of kilometres over sea ice searching for mates and hunting for seals, which are their primary prey. Recently, decreased sea ice extent and earlier ice break-up have been linked to shifts in seal distribution and abundance and to declines in polar bear condition and numbers in the western Hudson Bay polar bear population. We used geographic positioning system and satellite collars deployed between 1991 and 2004 to quantify movement patterns of adult female polar bears on the sea ice of Hudson Bay in relation to reproductive class and temporal variations in sea ice patterns. We tested whether reproductive status and season affected movement and whether temporal changes in movement were correlated with temporal changes in sea ice patterns in Hudson Bay. Movement patterns were not dependent on reproductive status but did change significantly with season. Annual distances moved and areas covered by bears in Hudson Bay have decreased since 1991, which suggests that measured declines in bear condition and numbers are due to reduced prey intake as opposed to increased energy output. These declines in bear movement are correlated with progressively earlier ice break-up in western Hudson Bay.

scholarly journals Trends in body condition in polar bears (Ursus maritimus) from the Southern Hudson Bay subpopulation in relation to changes in sea ice

2016 ◽  
Vol 2 (1) ◽  
pp. 15-32 ◽  
Author(s):  
M.E. Obbard ◽  
M.R.L. Cattet ◽  
E.J. Howe ◽  
K.R. Middel ◽  
E.J. Newton ◽  
...  
Keyword(s):  
Sea Ice ◽  
Body Condition ◽  
Survival Rates ◽  
Ursus Maritimus ◽  
Social Classes ◽  
The Arctic ◽  
Hudson Bay ◽  
Polar Bears ◽  
Western Hudson Bay ◽  
Break Up

Sea ice is declining over much of the Arctic. In Hudson Bay the ice melts completely each summer, and advances in break-up have resulted in longer ice-free seasons. Consequently, earlier break-up is implicated in declines in body condition, survival, and abundance of polar bears (Ursus maritimus Phipps, 1774) in the Western Hudson Bay (WH) subpopulation. We hypothesised that similar patterns would be evident in the neighbouring Southern Hudson Bay (SH) subpopulation. We examined trends 1980–2012 in break-up and freeze-up dates within the entire SH management unit and within smaller coastal break-up and freeze-up zones. We examined trends in body condition for 900 bears captured during 1984–1986, 2000–2005, and 2007–2009 and hypothesised that body condition would be correlated with duration of sea ice. The ice-free season in SH increased by about 30 days from 1980 to 2012. Body condition declined in all age and sex classes, but the decline was less for cubs than for other social classes. If trends towards a longer ice-free season continue in the future, further declines in body condition and survival rates are likely, and ultimately declines in abundance will occur in the SH subpopulation.

Future sea ice conditions in Western Hudson Bay and consequences for polar bears in the 21st century

2013 ◽  
Vol 19 (9) ◽  
pp. 2675-2687 ◽  
Author(s):  
Laura Castro de la Guardia ◽  
Andrew E. Derocher ◽  
Paul G. Myers ◽  
Arjen D. Terwisscha van Scheltinga ◽  
Nick J. Lunn
Keyword(s):  
Sea Ice ◽  
21St Century ◽  
Hudson Bay ◽  
Polar Bears ◽  
Ice Conditions ◽  
Western Hudson Bay

Sea ice cycle in western Hudson Bay, Canada, from a polar bear perspective

2017 ◽  
Vol 564 ◽  
pp. 225-233 ◽  
Author(s):  
L Castro de la Guardia ◽  
PG Myers ◽  
AE Derocher ◽  
NJ Lunn ◽  
AD Terwisscha van Scheltinga
Keyword(s):  
Sea Ice ◽  
Polar Bear ◽  
Hudson Bay ◽  
Western Hudson Bay

Effects of Earlier Sea Ice Breakup on Survival and Population Size of Polar Bears in Western Hudson Bay

2007 ◽  
Vol 71 (8) ◽  
pp. 2673-2683 ◽  
Author(s):  
ERIC V. REGEHR ◽  
NICHOLAS J. LUNN ◽  
STEVEN C. AMSTRUP ◽  
IAN STIRLING
Keyword(s):  
Sea Ice ◽  
Population Size ◽  
Hudson Bay ◽  
Polar Bears ◽  
Ice Breakup ◽  
Western Hudson Bay

scholarly journals The influence of sea ice dynamics on population energetics of Western Hudson Bay polar bears

Authorea ◽  
2020 ◽  
Author(s):  
Amy Johnson ◽  
Jody Reimer ◽  
Nicholas Lunn ◽  
Ian Stirling ◽  
David McGeachy ◽  
...  
Keyword(s):  
Sea Ice ◽  
Hudson Bay ◽  
Polar Bears ◽  
Ice Dynamics ◽  
Sea Ice Dynamics ◽  
Western Hudson Bay ◽  
Population Energetics

Distribution of polar bears (Ursus maritimus) during the ice-free period in western Hudson Bay

1990 ◽  
Vol 68 (7) ◽  
pp. 1395-1403 ◽  
Author(s):  
Andrew E. Derocher ◽  
Ian Stirling
Keyword(s):  
Energy Conservation ◽  
Sea Ice ◽  
Ursus Maritimus ◽  
North Coast ◽  
Hudson Bay ◽  
Polar Bears ◽  
Adult Males ◽  
The North ◽  
Western Hudson Bay ◽  
Age And Sex

The distribution and movements of polar bears (Ursus maritimus) during the ice-free period in western Hudson Bay were studied using mark and recapture and radiotelemetry locating of animals of known age and sex collected between 1966 and 1987. Polar bears segregated themselves by age, sex, and reproductive status. Adult males occupied coastal areas. Family groups and pregnant females occupied areas farther inland. Subadult females and males occupied similar habitats which overlapped with those of adult males. Avoidance of conspecifics, energy conservation, philopatry, denning habitat, and habitat selection appeared to influence observed patterns. A southward shift in the population was evident early in the ice-free period and was followed by a return movement northward during October and November. This may be due to ice-formation patterns which permit earlier access to the sea ice along the north coast and hunting habitat to the northeast. All bears moved less than bears on the sea ice, and movements were consistent with a strategy of energy conservation. Most bears appear to have travelled directly from the sea ice to the study area and remained until the sea ice reformed. Little exchange with adjacent populations and a high degree of philopatry were evident for all age and sex groups; this may be a function of the distribution of denning habitat, the winter distribution of sea ice habitat and seals, and the noncompetitive conditions that prevail during the ice-free period which make dispersal of limited benefit.

Distribution and abundance of ringed (Phoca hispida) and bearded seals (Erignathus barbatus) in western Hudson Bay

1997 ◽  
Vol 54 (4) ◽  
pp. 914-921 ◽  
Author(s):  
N J Lunn ◽  
I Stirling ◽  
S N Nowicki
Keyword(s):  
Polar Bear ◽  
Hudson Bay ◽  
Phoca Hispida ◽  
Current Estimate ◽  
Ringed Seals ◽  
Erignathus Barbatus ◽  
The Mean ◽  
Western Hudson Bay ◽  
The Relationship ◽  
Bearded Seals

We flew a medium-altitude, systematic, strip-transect survey for ringed (Phoca hispida) and bearded seals (Erignathus barbatus) over western Hudson Bay in early June 1994 and 1995. The mean density (per square kilometre) of ringed seals hauled out on the ice was four times higher in 1995 (1.690) than in 1994 (0.380). The 1994 survey appeared to underestimate seal abundance because it was flown too late. Ringed seals preferred high ice cover habitat (6 + /8 ice) and, within this habitat, favoured cracking ice and large floes. We found no consistent effect of either wind or cloud cover on habitat preference. We estimated a total of 1980 bearded seals and 140<|>880 ringed seals hauled out on the sea ice in June 1995. A recent review of the relationship between ringed seal and polar bear (Ursus maritimus) populations suggests that a visible population of this size should support a population of up to 1300 polar bears, which is in general agreement with the current estimate of 1250-1300 bears in western Hudson Bay.

scholarly journals Conservation status of polar bears ( Ursus maritimus ) in relation to projected sea-ice declines

2016 ◽  
Vol 12 (12) ◽  
pp. 20160556 ◽  
Author(s):  
Eric V. Regehr ◽  
Kristin L. Laidre ◽  
H. Resit Akçakaya ◽  
Steven C. Amstrup ◽  
Todd C. Atwood ◽  
...  
Keyword(s):  
Sea Ice ◽  
Polar Bear ◽  
Extinction Risk ◽  
Conservation Status ◽  
Iucn Red List ◽  
Arctic Sea Ice ◽  
Polar Bears ◽  
Near Term ◽  
Conservation Assessments ◽  
Global Population

Loss of Arctic sea ice owing to climate change is the primary threat to polar bears throughout their range. We evaluated the potential response of polar bears to sea-ice declines by (i) calculating generation length (GL) for the species, which determines the timeframe for conservation assessments; (ii) developing a standardized sea-ice metric representing important habitat; and (iii) using statistical models and computer simulation to project changes in the global population under three approaches relating polar bear abundance to sea ice. Mean GL was 11.5 years. Ice-covered days declined in all subpopulation areas during 1979–2014 (median −1.26 days year −1 ). The estimated probabilities that reductions in the mean global population size of polar bears will be greater than 30%, 50% and 80% over three generations (35–41 years) were 0.71 (range 0.20–0.95), 0.07 (range 0–0.35) and less than 0.01 (range 0–0.02), respectively. According to IUCN Red List reduction thresholds, which provide a common measure of extinction risk across taxa, these results are consistent with listing the species as vulnerable. Our findings support the potential for large declines in polar bear numbers owing to sea-ice loss, and highlight near-term uncertainty in statistical projections as well as the sensitivity of projections to different plausible assumptions.

Heritability of body size in the polar bears of Western Hudson Bay

2018 ◽  
Vol 18 (4) ◽  
pp. 854-866 ◽  
Author(s):  
René M. Malenfant ◽  
Corey S. Davis ◽  
Evan S. Richardson ◽  
Nicholas J. Lunn ◽  
David W. Coltman
Keyword(s):  
Body Size ◽  
Hudson Bay ◽  
Polar Bears ◽  
Western Hudson Bay
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