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Andrew E. Derocher - One of the best experts on this subject based on the ideXlab platform.
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Polar Bear denning distribution in the Canadian Arctic
Polar Biology, 2020Co-Authors: Katie R. N. Florko, Andrew E. Derocher, Daryll Hedman, C-jae C. Breiter, Maha Ghazal, Jeff W. Higdon, Evan S. Richardson, Vicki Sahanatien, Vicki Trim, Stephen D. PetersenAbstract:Declines in Arctic sea ice associated with climate change have resulted in habitat loss for ice-adapted species, while facilitating increased human development at higher latitudes. Development increases land-use and shipping traffic, which can threaten ecologically and culturally important species. Female Polar Bears ( Ursus maritimus ) and cubs are susceptible to disturbance during denning; a better understanding of denning habitat distribution may aid management. We compiled existing location data on Polar Bear denning ( n = 64 sources) in Canada between 1967 and 2018, including traditional ecological knowledge (TEK) studies, government and consultant reports, peer-reviewed scientific articles, and unpublished data acquired through data-sharing agreements. We synthesized these data to create a map of known denning locations. Most coastal regions in northern Canada supported denning, but large areas exist where denning is unreported. Gaps remain in the knowledge of Polar Bear denning in Canada and filling these will aid the conservation and management of Polar Bears in a changing Arctic.
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Projected Polar Bear Sea Ice Habitat in the Canadian Arctic Archipelago
PloS one, 2014Co-Authors: Stephen G. Hamilton, Andrew E. Derocher, Vicki Sahanatien, Laura Castro De La Guardia, Bruno Tremblay, David HuardAbstract:Background Sea ice across the Arctic is declining and altering physical characteristics of marine ecosystems. Polar Bears (Ursus maritimus) have been identified as vulnerable to changes in sea ice conditions. We use sea ice projections for the Canadian Arctic Archipelago from 2006 – 2100 to gain insight into the conservation challenges for Polar Bears with respect to habitat loss using metrics developed from Polar Bear energetics modeling. Principal Findings Shifts away from multiyear ice to annual ice cover throughout the region, as well as lengthening ice-free periods, may become critical for Polar Bears before the end of the 21st century with projected warming. Each Polar Bear population in the Archipelago may undergo 2–5 months of ice-free conditions, where no such conditions exist presently. We identify spatially and temporally explicit ice-free periods that extend beyond what Polar Bears require for nutritional and reproductive demands. Conclusions/Significance Under business-as-usual climate projections, Polar Bears may face starvation and reproductive failure across the entire Archipelago by the year 2100.
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monitoring sea ice habitat fragmentation for Polar Bear conservation
Animal Conservation, 2012Co-Authors: Vicki Sahanatien, Andrew E. DerocherAbstract:Polar Bears are a sea ice-dependent carnivore, sensitive to sea ice habitat loss. Climate change has negatively affected sea ice habitat through much of this species' range. We applied landscape fragmentation analysis to quantify Polar Bear sea ice habitat loss and fragmentation trends (1979–2008) in Foxe Basin, Hudson Strait and Hudson Bay, Canada. Microwave satellite derived monthly mean sea ice concentration maps were classified into four habitat quality categories, and the trends in fragmentation metrics were analyzed. In all regions where preferred habitat declined, sea ice season length decreased and habitat fragmentation increased. The observed trends may affect Polar Bear movement patterns, energetics and ultimately population trends. Monitoring of sea ice habitat condition in combination with harvest data can provide a dynamic approach to population management and conservation.
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predicting climate change impacts on Polar Bear litter size
Nature Communications, 2011Co-Authors: Peter K Molnar, Tin Klanjscek, Andrew E. Derocher, Mark A. LewisAbstract:Predicting the ecological impacts of climate warming is critical for species conservation. Incorporating future warming into population models, however, is challenging because reproduction and survival cannot be measured for yet unobserved environmental conditions. In this study, we use mechanistic energy budget models and data obtainable under current conditions to predict Polar Bear litter size under future conditions. In western Hudson Bay, we predict climate warming-induced litter size declines that jeopardize population viability: ∼28% of pregnant females failed to reproduce for energetic reasons during the early 1990s, but 40–73% could fail if spring sea ice break-up occurs 1 month earlier than during the 1990s, and 55–100% if break-up occurs 2 months earlier. Simultaneously, mean litter size would decrease by 22–67% and 44–100%, respectively. The expected timeline for these declines varies with climate-model-specific sea ice predictions. Similar litter size declines may occur in over one-third of the global Polar Bear population. Predicting ecological impacts of climate change is complicated, because key biological parameters are unknown for future conditions. Using a mechanistic energy budget model to relate sea ice to Polar Bear reproduction, Molnaret al.predict decreases in litter size with anticipated changes in sea ice.
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predicting climate change impacts on Polar Bear litter size
Nature Communications, 2011Co-Authors: Peter K Molnar, Tin Klanjscek, Andrew E. Derocher, Mark A. LewisAbstract:Predicting the ecological impacts of climate warming is critical for species conservation. Incorporating future warming into population models, however, is challenging because reproduction and survival cannot be measured for yet unobserved environmental conditions. In this study, we use mechanistic energy budget models and data obtainable under current conditions to predict Polar Bear litter size under future conditions. In western Hudson Bay, we predict climate warming-induced litter size declines that jeopardize population viability: ∼28% of pregnant females failed to reproduce for energetic reasons during the early 1990s, but 40-73% could fail if spring sea ice break-up occurs 1 month earlier than during the 1990s, and 55-100% if break-up occurs 2 months earlier. Simultaneously, mean litter size would decrease by 22-67% and 44-100%, respectively. The expected timeline for these declines varies with climate-model-specific sea ice predictions. Similar litter size declines may occur in over one-third of the global Polar Bear population.
Steven C. Amstrup - One of the best experts on this subject based on the ideXlab platform.
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fasting season length sets temporal limits for global Polar Bear persistence
Nature Climate Change, 2020Co-Authors: Peter K Molnar, Cecilia M Bitz, Marika M Holland, Jennifer E Kay, Stephanie R Penk, Steven C. AmstrupAbstract:Polar Bears (Ursus maritimus) require sea ice for capturing seals and are expected to decline range-wide as global warming and sea-ice loss continue1,2. Estimating when different subpopulations will likely begin to decline has not been possible to date because data linking ice availability to demographic performance are unavailable for most subpopulations2 and unobtainable a priori for the projected but yet-to-be-observed low ice extremes3. Here, we establish the likely nature, timing and order of future demographic impacts by estimating the threshold numbers of days that Polar Bears can fast before cub recruitment and/or adult survival are impacted and decline rapidly. Intersecting these fasting impact thresholds with projected numbers of ice-free days, estimated from a large ensemble of an Earth system model4, reveals when demographic impacts will likely occur in different subpopulations across the Arctic. Our model captures demographic trends observed during 1979–2016, showing that recruitment and survival impact thresholds may already have been exceeded in some subpopulations. It also suggests that, with high greenhouse gas emissions, steeply declining reproduction and survival will jeopardize the persistence of all but a few high-Arctic subpopulations by 2100. Moderate emissions mitigation prolongs persistence but is unlikely to prevent some subpopulation extirpations within this century. Polar Bear numbers are expected to decline as the sea ice they rely on to catch their prey declines with global warming. Projections show when fasts caused by declining sea ice are likely to lead to rapid recruitment and survival declines across the Polar Bear circumPolar range.
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efficacy of aerial forward looking infrared surveys for detecting Polar Bear maternal dens
PLOS ONE, 2020Co-Authors: Tom S Smith, Steven C. Amstrup, B J Kirschhoffer, G S YorkAbstract:Denned Polar Bears (Ursus maritimus) are invisible under the snow, therefore winter-time petroleum exploration and development activities in northern Alaska have potential to disturb maternal Polar Bears and their cubs. Previous research determined forward looking infrared (FLIR) imagery could detect many Polar Bear maternal dens under the snow, but also identified limitations of FLIR imagery. We evaluated the efficacy of FLIR-surveys conducted by oil-field operators from 2004-2016. Aerial FLIR surveys detected 15 of 33 (45%) and missed 18 (55%) of the dens known to be within surveyed areas. While greater adherence to previously recommended protocols may improve FLIR detection rates, the physical characteristics of Polar Bear maternal dens, increasing frequencies of weather unsuitable for FLIR detections-caused by global warming, and competing false positives are likely to prevent FLIR surveys from detecting maternal dens reliably enough to afford protections consonant with increasing global threats to Polar Bear welfare.
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efficacy of aerial forward looking infrared surveys for detecting Polar Bear maternal dens
bioRxiv, 2019Co-Authors: Tom S Smith, Steven C. Amstrup, B J Kirschhoffer, G S YorkAbstract:Abstract Denned Polar Bears are invisible under the snow, therefore winter-time petroleum exploration and development activities in northern Alaska have potential to disturb maternal Polar Bears and their cubs. Previous research determined forward looking infrared (FLIR) imagery could detect many Polar Bear maternal dens under the snow, but also identified limitations of FLIR imagery. We evaluated the efficacy of FLIR-surveys conducted by oil-field operators from 2004-2016. Aerial FLIR surveys detected 15 of 33 (45%) and missed 18 (55%) of the dens known to be within surveyed areas. While greater adherence to previously recommended protocols may improve FLIR detection rates, the physical characteristics of Polar Bear maternal dens, increasing frequencies of weather unsuitable for FLIR detections—caused by global warming, and competing “hot spots” are likely to prevent FLIR surveys from detecting maternal dens reliably enough to afford protections consonant with increasing global threats to Polar Bear welfare.
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greenhouse gas mitigation can reduce sea ice loss and increase Polar Bear persistence
Nature, 2010Co-Authors: Steven C. Amstrup, George M. Durner, David C Douglas, Eric T Deweaver, Bruce G Marcot, Cecilia M Bitz, David A BaileyAbstract:Polar Bears live only in marine regions of the Northern Hemisphere where sea-ice cover persists for long enough to allow them sufficient opportunity to access their marine mammal prey. Recent declines in summer Arctic sea ice have coincided with declines in some Polar Bear populations, and a US Geological Survey report in 2007 projected that with 'business as usual' emissions, Polar Bears could be extinct throughout their range by the end of the century. Some observers have suggested that summer Arctic sea ice might already have crossed a tipping point from beyond which habitats might not recover. But a new analysis suggests that it is not too late to save the Polar Bear. The rapid summer ice losses seen of late may represent increased volatility of a thinning sea-ice cover, rather than a tipping point. Greenhouse-gas mitigation could yet halt sea-ice loss and preserve the Arctic ecosystem. The dramatic loss of Arctic sea ice with climate change has led to the prediction of a tipping point beyond which ice loss is irreversible and Polar Bear habitat will be catastrophically lost. By contrast, this study shows a linear relationship between temperature and sea-ice coverage that overcomes the albedo effect that would cause a tipping point. As a result, reducing greenhouse gas emissions can have a positive effect on Polar Bear populations. On the basis of projected losses of their essential sea-ice habitats, a United States Geological Survey research team concluded in 2007 that two-thirds of the world’s Polar Bears (Ursus maritimus) could disappear by mid-century if business-as-usual greenhouse gas emissions continue1,2,3. That projection, however, did not consider the possible benefits of greenhouse gas mitigation. A key question is whether temperature increases lead to proportional losses of sea-ice habitat, or whether sea-ice cover crosses a tipping point and irreversibly collapses when temperature reaches a critical threshold4,5,6. Such a tipping point would mean future greenhouse gas mitigation would confer no conservation benefits to Polar Bears. Here we show, using a general circulation model7, that substantially more sea-ice habitat would be retained if greenhouse gas rise is mitigated. We also show, with Bayesian network model outcomes, that increased habitat retention under greenhouse gas mitigation means that Polar Bears could persist throughout the century in greater numbers and more areas than in the business-as-usual case3. Our general circulation model outcomes did not reveal thresholds leading to irreversible loss of ice6; instead, a linear relationship between global mean surface air temperature and sea-ice habitat substantiated the hypothesis that sea-ice thermodynamics can overcome albedo feedbacks proposed to cause sea-ice tipping points5,6,8. Our outcomes indicate that rapid summer ice losses in models9 and observations6,10 represent increased volatility of a thinning sea-ice cover, rather than tipping-point behaviour. Mitigation-driven Bayesian network outcomes show that previously predicted declines in Polar Bear distribution and numbers3 are not unavoidable. Because Polar Bears are sentinels of the Arctic marine ecosystem11 and trends in their sea-ice habitats foreshadow future global changes, mitigating greenhouse gas emissions to improve Polar Bear status would have conservation benefits throughout and beyond the Arctic12.
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climate change threatens Polar Bear populations a stochastic demographic analysis
Ecology, 2010Co-Authors: Christine M Hunter, Michael C Runge, Eric V. Regehr, Steven C. Amstrup, Hal Caswell, Ian StirlingAbstract:The Polar Bear (Ursus maritimus) depends on sea ice for feeding, breeding, and movement. Significant reductions in Arctic sea ice are forecast to continue because of climate warming. We evaluated the impacts of climate change on Polar Bears in the southern Beaufort Sea by means of a demographic analysis, combining deterministic, stochastic, environment- dependent matrix population models with forecasts of future sea ice conditions from IPCC general circulation models (GCMs). The matrix population models classified individuals by age and breeding status; mothers and dependent cubs were treated as units. Parameter estimates were obtained from a capture-recapture study conducted from 2001 to 2006. Candidate statistical models allowed vital rates to vary with time and as functions of a sea ice covariate. Model averaging was used to produce the vital rate estimates, and a parametric bootstrap procedure was used to quantify model selection and parameter estimation uncertainty. Deterministic models projected population growth in years with more extensive ice coverage (2001-2003) and population decline in years with less ice coverage (2004-2005). LTRE (life table response experiment) analysis showed that the reduction in k in years with low sea ice was due primarily to reduced adult female survival, and secondarily to reduced breeding. A stochastic model with two environmental states, good and poor sea ice conditions, projected a declining stochastic growth rate, log ks, as the frequency of poor ice years increased. The observed frequency of poor ice years since 1979 would imply log ks ' � 0.01, which agrees with available (albeit crude) observations of population size. The stochastic model was linked to a set of 10 GCMs compiled by the IPCC; the models were chosen for their ability to reproduce historical observations of sea ice and were forced with ''business as usual'' (A1B) greenhouse gas emissions. The resulting stochastic population projections showed drastic declines in the Polar Bear population by the end of the 21st century. These projections were instrumental in the decision to list the Polar Bear as a threatened species under the U.S. Endangered Species Act.
Peter K Molnar - One of the best experts on this subject based on the ideXlab platform.
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fasting season length sets temporal limits for global Polar Bear persistence
Nature Climate Change, 2020Co-Authors: Peter K Molnar, Cecilia M Bitz, Marika M Holland, Jennifer E Kay, Stephanie R Penk, Steven C. AmstrupAbstract:Polar Bears (Ursus maritimus) require sea ice for capturing seals and are expected to decline range-wide as global warming and sea-ice loss continue1,2. Estimating when different subpopulations will likely begin to decline has not been possible to date because data linking ice availability to demographic performance are unavailable for most subpopulations2 and unobtainable a priori for the projected but yet-to-be-observed low ice extremes3. Here, we establish the likely nature, timing and order of future demographic impacts by estimating the threshold numbers of days that Polar Bears can fast before cub recruitment and/or adult survival are impacted and decline rapidly. Intersecting these fasting impact thresholds with projected numbers of ice-free days, estimated from a large ensemble of an Earth system model4, reveals when demographic impacts will likely occur in different subpopulations across the Arctic. Our model captures demographic trends observed during 1979–2016, showing that recruitment and survival impact thresholds may already have been exceeded in some subpopulations. It also suggests that, with high greenhouse gas emissions, steeply declining reproduction and survival will jeopardize the persistence of all but a few high-Arctic subpopulations by 2100. Moderate emissions mitigation prolongs persistence but is unlikely to prevent some subpopulation extirpations within this century. Polar Bear numbers are expected to decline as the sea ice they rely on to catch their prey declines with global warming. Projections show when fasts caused by declining sea ice are likely to lead to rapid recruitment and survival declines across the Polar Bear circumPolar range.
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predicting climate change impacts on Polar Bear litter size
Nature Communications, 2011Co-Authors: Peter K Molnar, Tin Klanjscek, Andrew E. Derocher, Mark A. LewisAbstract:Predicting the ecological impacts of climate warming is critical for species conservation. Incorporating future warming into population models, however, is challenging because reproduction and survival cannot be measured for yet unobserved environmental conditions. In this study, we use mechanistic energy budget models and data obtainable under current conditions to predict Polar Bear litter size under future conditions. In western Hudson Bay, we predict climate warming-induced litter size declines that jeopardize population viability: ∼28% of pregnant females failed to reproduce for energetic reasons during the early 1990s, but 40–73% could fail if spring sea ice break-up occurs 1 month earlier than during the 1990s, and 55–100% if break-up occurs 2 months earlier. Simultaneously, mean litter size would decrease by 22–67% and 44–100%, respectively. The expected timeline for these declines varies with climate-model-specific sea ice predictions. Similar litter size declines may occur in over one-third of the global Polar Bear population. Predicting ecological impacts of climate change is complicated, because key biological parameters are unknown for future conditions. Using a mechanistic energy budget model to relate sea ice to Polar Bear reproduction, Molnaret al.predict decreases in litter size with anticipated changes in sea ice.
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predicting climate change impacts on Polar Bear litter size
Nature Communications, 2011Co-Authors: Peter K Molnar, Tin Klanjscek, Andrew E. Derocher, Mark A. LewisAbstract:Predicting the ecological impacts of climate warming is critical for species conservation. Incorporating future warming into population models, however, is challenging because reproduction and survival cannot be measured for yet unobserved environmental conditions. In this study, we use mechanistic energy budget models and data obtainable under current conditions to predict Polar Bear litter size under future conditions. In western Hudson Bay, we predict climate warming-induced litter size declines that jeopardize population viability: ∼28% of pregnant females failed to reproduce for energetic reasons during the early 1990s, but 40-73% could fail if spring sea ice break-up occurs 1 month earlier than during the 1990s, and 55-100% if break-up occurs 2 months earlier. Simultaneously, mean litter size would decrease by 22-67% and 44-100%, respectively. The expected timeline for these declines varies with climate-model-specific sea ice predictions. Similar litter size declines may occur in over one-third of the global Polar Bear population.
Mark A. Lewis - One of the best experts on this subject based on the ideXlab platform.
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predicting climate change impacts on Polar Bear litter size
Nature Communications, 2011Co-Authors: Peter K Molnar, Tin Klanjscek, Andrew E. Derocher, Mark A. LewisAbstract:Predicting the ecological impacts of climate warming is critical for species conservation. Incorporating future warming into population models, however, is challenging because reproduction and survival cannot be measured for yet unobserved environmental conditions. In this study, we use mechanistic energy budget models and data obtainable under current conditions to predict Polar Bear litter size under future conditions. In western Hudson Bay, we predict climate warming-induced litter size declines that jeopardize population viability: ∼28% of pregnant females failed to reproduce for energetic reasons during the early 1990s, but 40–73% could fail if spring sea ice break-up occurs 1 month earlier than during the 1990s, and 55–100% if break-up occurs 2 months earlier. Simultaneously, mean litter size would decrease by 22–67% and 44–100%, respectively. The expected timeline for these declines varies with climate-model-specific sea ice predictions. Similar litter size declines may occur in over one-third of the global Polar Bear population. Predicting ecological impacts of climate change is complicated, because key biological parameters are unknown for future conditions. Using a mechanistic energy budget model to relate sea ice to Polar Bear reproduction, Molnaret al.predict decreases in litter size with anticipated changes in sea ice.
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predicting climate change impacts on Polar Bear litter size
Nature Communications, 2011Co-Authors: Peter K Molnar, Tin Klanjscek, Andrew E. Derocher, Mark A. LewisAbstract:Predicting the ecological impacts of climate warming is critical for species conservation. Incorporating future warming into population models, however, is challenging because reproduction and survival cannot be measured for yet unobserved environmental conditions. In this study, we use mechanistic energy budget models and data obtainable under current conditions to predict Polar Bear litter size under future conditions. In western Hudson Bay, we predict climate warming-induced litter size declines that jeopardize population viability: ∼28% of pregnant females failed to reproduce for energetic reasons during the early 1990s, but 40-73% could fail if spring sea ice break-up occurs 1 month earlier than during the 1990s, and 55-100% if break-up occurs 2 months earlier. Simultaneously, mean litter size would decrease by 22-67% and 44-100%, respectively. The expected timeline for these declines varies with climate-model-specific sea ice predictions. Similar litter size declines may occur in over one-third of the global Polar Bear population.
Øystein Wiig - One of the best experts on this subject based on the ideXlab platform.
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establishing a definition of Polar Bear ursus maritimus health a guide to research and management activities
Science of The Total Environment, 2015Co-Authors: Kelly A Patyk, Eric V. Regehr, Kristin L Laidre, Martyn E. Obbard, Øystein Wiig, Jon Aars, Colleen Duncan, Pauline Nol, Christian Sonne, L GustafsonAbstract:The meaning of health for wildlife and perspectives on how to assess and measure health, are not well characterized. For wildlife at risk, such as some Polar Bear (Ursus maritimus) subpopulations, establishing comprehensive monitoring programs that include health status is an emerging need. Environmental changes, especially loss of sea ice habitat, have raised concern about Polar Bear health. Effective and consistent monitoring of Polar Bear health requires an unambiguous definition of health. We used the Delphi method of soliciting and interpreting expert knowledge to propose a working definition of Polar Bear health and to identify current concerns regarding health, challenges in measuring health, and important metrics for monitoring health. The expert opinion elicited through the exercise agreed that Polar Bear health is defined by characteristics and knowledge at the individual, population, and ecosystem level. The most important threats identified were in decreasing order: climate change, increased nutritional stress, chronic physiological stress, harvest management, increased exposure to contaminants, increased frequency of human interaction, diseases and parasites, and increased exposure to competitors. Fifteen metrics were identified to monitor Polar Bear health. Of these, indicators of body condition, disease and parasite exposure, contaminant exposure, and reproductive success were ranked as most important. We suggest that a cumulative effects approach to research and monitoring will improve the ability to assess the biological, ecological, and social determinants of Polar Bear health and provide measurable objectives for conservation goals and priorities and to evaluate progress.
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predicting 21st century Polar Bear habitat distribution from global climate models
Ecological Monographs, 2009Co-Authors: George M. Durner, Steven C. Amstrup, Ian Stirling, Mette Mauritzen, Øystein Wiig, David C Douglas, Ryan M Nielson, Trent L Mcdonald, Erik W Born, Eric DeweaverAbstract:Projections of Polar Bear (Ursus maritimus) sea ice habitat distribution in the Polar basin during the 21st century were developed to understand the consequences of anticipated sea ice reductions on Polar Bear populations. We used location data from satellite- collared Polar Bears and environmental data (e.g., bathymetry, distance to coastlines, and sea ice) collected from 1985 to 1995 to build resource selection functions (RSFs). RSFs described habitats that Polar Bears preferred in summer, autumn, winter, and spring. When applied to independent data from 1996 to 2006, the RSFs consistently identified habitats most frequently used by Polar Bears. We applied the RSFs to monthly maps of 21st-century sea ice concentration projected by 10 general circulation models (GCMs) used in the Intergovern- mental Panel of Climate Change Fourth Assessment Report, under the A1B greenhouse gas forcing scenario. Despite variation in their projections, all GCMs indicated habitat losses in the Polar basin during the 21st century. Losses in the highest-valued RSF habitat (optimal habitat) were greatest in the southern seas of the Polar basin, especially the Chukchi and Barents seas, and least along the Arctic Ocean shores of Banks Island to northern Greenland. Mean loss of optimal Polar Bear habitat was greatest during summer; from an observed 1.0 million km 2 in 1985-1995 (baseline) to a projected multi-model mean of 0.32 million km 2 in 2090-2099 (� 68% change). Projected winter losses of Polar Bear habitat were less: from 1.7 million km 2 in 1985-1995 to 1.4 million km 2 in 2090-2099 (� 17% change). Habitat losses based on GCM multi-model means may be conservative; simulated rates of habitat loss during 1985-2006 from many GCMs were less than the actual observed rates of loss. Although a reduction in the total amount of optimal habitat will likely reduce Polar Bear populations, exact relationships between habitat losses and population demographics remain unknown. Density and energetic effects may become important as Polar Bears make long-distance annual migrations from traditional winter ranges to remnant high-latitude summer sea ice. These impacts will likely affect specific sex and age groups differently and may ultimately preclude Bears from seasonally returning to their traditional ranges.
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estimating the barents sea Polar Bear subpopulation size
Marine Mammal Science, 2009Co-Authors: Jon Aars, Stanislav Belikov, Andrei N. Boltunov, Tiago A Marques, Stephen T Buckland, Magnus Andersen, Øystein WiigAbstract:A large-scale survey was conducted in August 2004 to estimate the size of the Barents Sea Polar Bear subpopulation. We combined helicopter line transect distance sampling (DS) surveys in most of the survey area with total counts in small areas not suitable for DS. Due to weather constraints we failed to survey some of the areas originally planned to be covered by DS. For those, abundance was estimated using a ratio estimator, in which the auxiliary variable was the number of satellite telemetry fixes (in previous years). We estimated that the Barents Sea subpopulation had approximately 2,650 (95% CI approximately 1,900–3,600) Bears. Given current intense interest in Polar Bear management due to the potentially disastrous effects of climate change, it is surprising that many subpopulation sizes are still unknown. We show here that line transect sampling is a promising method for addressing the need for abundance estimates.
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Functional responses in Polar Bear habitat selection
Oikos, 2003Co-Authors: Mette Mauritzen, Andrew E. Derocher, Stanislav Belikov, Andrei N. Boltunov, Edmond Hansen, Rolf A. Ims, Øystein Wiig, Nigel G. YoccozAbstract:Habitat selection may occur in situations in which animals experience a trade-off, e.g. between the use of habitats with abundant forage and the use of safer retreat habitats with little forage. Such trade-offs may yield relative habitat use conditional on the relative availability of the different habitat types, as proportional use of foraging habitat may exceed proportional availability when foraging habitat is scarce, but be less than availability when foraging habitat is abundant. Hence, trade-offs in habitat use may result in functional responses in habitat use (i.e. change in relative use with changing availability). We used logistic and log-linear models to model functional responses in female Polar Bear habitat use based on satellite telemetry data from two contiguous populations; one near shore inhabiting sea ice within fjords, and one inhabiting pelagic drift ice. Open ice, near the ice edge, is a highly dynamic habitat hypothesised to be important Polar Bear habitat due to high prey availability. In open ice-Polar Bears may experience a high energetic cost of movements and risk drifting away from the main ice field (i.e. trade off between feeding and energy saving or safety). If Polar Bears were constrained by ice dynamics we therefore predicted use of retreat habitats with greater ice coverage relative to habitats used for hunting. The Polar Bears demonstrated season and population specific functional responses in habitat use, likely reflecting seasonal and regional variation in use of retreat and foraging habitats. We suggest that in seasons with functional responses in habitat use, Polar Bear space use and population distribution may not be a mere reflection of prey availability but rather reflect the alternate allocation of time in hunting and retreat habitats.
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genetic structure of the world s Polar Bear populations
Molecular Ecology, 1999Co-Authors: David Paetkau, Steven C. Amstrup, Ian Stirling, Andrew E. Derocher, Mitchell K. Taylor, Erik W Born, Wendy Calvert, G W Garner, Francois Messier, Øystein WiigAbstract:We studied genetic structure in Polar Bear (Ursus maritimus) populations by typing a sample of 473 individuals spanning the species distribution at 16 highly variable microsatellite loci. No genetic discontinuities were found that would be consistent with evolutionarily significant periods of isolation between groups. Direct comparison of movement data and genetic data from the Canadian Arctic revealed a highly significant correlation. Genetic data generally supported existing population (management unit) designations, although there were two cases where genetic data failed to differentiate between pairs of populations previously resolved by movement data. A sharp contrast was found between the minimal genetic structure observed among populations surrounding the Polar basin and the presence of several marked genetic discontinuities in the Canadian Arctic. The discontinuities in the Canadian Arctic caused the appearance of four genetic clusters of Polar Bear populations. These clusters vary in total estimated population size from 100 to over 10 000, and the smallest may merit a relatively conservative management strategy in consideration of its apparent isolation. We suggest that the observed pattern of genetic discontinuities has developed in response to differences in the seasonal distribution and pattern of sea ice habitat and the effects of these differences on the distribution and abundance of seals.
