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Arctic marine mammal population status, sea ice habitat loss, and conservation recommendations for the 21st century.

https://arctichealth.org/en/permalink/ahliterature270034
Source
Conserv Biol. 2015 Jun;29(3):724-37
Publication Type
Article
Date
Jun-2015
Author
Kristin L Laidre
Harry Stern
Kit M Kovacs
Lloyd Lowry
Sue E Moore
Eric V Regehr
Steven H Ferguson
Øystein Wiig
Peter Boveng
Robyn P Angliss
Erik W Born
Dennis Litovka
Lori Quakenbush
Christian Lydersen
Dag Vongraven
Fernando Ugarte
Source
Conserv Biol. 2015 Jun;29(3):724-37
Date
Jun-2015
Language
English
Publication Type
Article
Keywords
Animals
Arctic Regions
Cetacea - physiology
Climate change
Conservation of Natural Resources
Ecosystem
Ice Cover
Pinnipedia - physiology
Population Density
Abstract
Arctic marine mammals (AMMs) are icons of climate change, largely because of their close association with sea ice. However, neither a circumpolar assessment of AMM status nor a standardized metric of sea ice habitat change is available. We summarized available data on abundance and trend for each AMM species and recognized subpopulation. We also examined species diversity, the extent of human use, and temporal trends in sea ice habitat for 12 regions of the Arctic by calculating the dates of spring sea ice retreat and fall sea ice advance from satellite data (1979-2013). Estimates of AMM abundance varied greatly in quality, and few studies were long enough for trend analysis. Of the AMM subpopulations, 78% (61 of 78) are legally harvested for subsistence purposes. Changes in sea ice phenology have been profound. In all regions except the Bering Sea, the duration of the summer (i.e., reduced ice) period increased by 5-10 weeks and by >20 weeks in the Barents Sea between 1979 and 2013. In light of generally poor data, the importance of human use, and forecasted environmental changes in the 21st century, we recommend the following for effective AMM conservation: maintain and improve comanagement by local, federal, and international partners; recognize spatial and temporal variability in AMM subpopulation response to climate change; implement monitoring programs with clear goals; mitigate cumulative impacts of increased human activity; and recognize the limits of current protected species legislation.
PubMed ID
25783745 View in PubMed
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Climate change threatens polar bear populations: a stochastic demographic analysis.

https://arctichealth.org/en/permalink/ahliterature100110
Source
Ecology. 2010 Oct;91(10):2883-97
Publication Type
Article
Date
Oct-2010
Author
Christine M Hunter
Hal Caswell
Michael C Runge
Eric V Regehr
Steve C Amstrup
Ian Stirling
Author Affiliation
Department of Biology and Wildlife, Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska 99775, USA. christine.hunter@alaska.edu
Source
Ecology. 2010 Oct;91(10):2883-97
Date
Oct-2010
Language
English
Publication Type
Article
Keywords
Animals
Arctic Regions
Canada
Climate change
Ecosystem
Endangered Species
Models, Biological
Population Dynamics
Stochastic Processes
Time Factors
Uncertainty
United States
Ursidae - physiology
Abstract
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 lambda 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 lambdas, as the frequency of poor ice years increased. The observed frequency of poor ice years since 1979 would imply log lambdas approximately - 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.
PubMed ID
21058549 View in PubMed
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Conservation status of polar bears (Ursus maritimus) in relation to projected sea-ice declines.

https://arctichealth.org/en/permalink/ahliterature277897
Source
Biol Lett. 2016 Dec;12(12)
Publication Type
Article
Date
Dec-2016
Author
Eric V Regehr
Kristin L Laidre
H Resit Akçakaya
Steven C Amstrup
Todd C Atwood
Nicholas J Lunn
Martyn Obbard
Harry Stern
Gregory W Thiemann
Øystein Wiig
Source
Biol Lett. 2016 Dec;12(12)
Date
Dec-2016
Language
English
Publication Type
Article
Abstract
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.
PubMed ID
27928000 View in PubMed
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Demography of an apex predator at the edge of its range: impacts of changing sea ice on polar bears in Hudson Bay.

https://arctichealth.org/en/permalink/ahliterature277135
Source
Ecol Appl. 2016 Jul;26(5):1302-1320
Publication Type
Article
Date
Jul-2016
Author
Nicholas J Lunn
Sabrina Servanty
Eric V Regehr
Sarah J Converse
Evan Richardson
Ian Stirling
Source
Ecol Appl. 2016 Jul;26(5):1302-1320
Date
Jul-2016
Language
English
Publication Type
Article
Abstract
Changes in the abundance and distribution of wildlife populations are common consequences of historic and contemporary climate change. Some Arctic marine mammals, such as the polar bear (Ursus maritimus), may be particularly vulnerable to such changes due to the loss of Arctic sea ice. We evaluated the impacts of environmental variation on demographic rates for the Western Hudson Bay (WH), polar bear subpopulation from 1984 to 2011 using live-recapture and dead-recovery data in a Bayesian implementation of multistate capture-recapture models. We found that survival of female polar bears was related to the annual timing of sea ice break-up and formation. Using estimated vital rates (e.g., survival and reproduction) in matrix projection models, we calculated the growth rate of the WH subpopulation and projected population responses under different environmental scenarios while accounting for parametric uncertainty, temporal variation, and demographic stochasticity. Our analysis suggested a long-term decline in the number of bears from 1185 (95% Bayesian credible interval [BCI] = 993-1411) in 1987 to 806 (95% BCI = 653-984) in 2011. In the last 10 yr of the study, the number of bears appeared stable due to temporary stability in sea ice conditions (mean population growth rate for the period 2001-2010 = 1.02, 95% BCI = 0.98-1.06). Looking forward, we estimated long-term growth rates for the WH subpopulation of ~1.02 (95% BCI = 1.00-1.05) and 0.97 (95% BCI = 0.92-1.01) under hypothetical high and low sea ice conditions, respectively. Our findings support previous evidence for a demographic linkage between sea ice conditions and polar bear population dynamics. Furthermore, we present a robust framework for sensitivity analysis with respect to continued climate change (e.g., to inform scenario planning) and for evaluating the combined effects of climate change and management actions on the status of wildlife populations.
PubMed ID
27755745 View in PubMed
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Habitat degradation affects the summer activity of polar bears.

https://arctichealth.org/en/permalink/ahliterature280504
Source
Oecologia. 2017 Feb 28;
Publication Type
Article
Date
Feb-28-2017
Author
Jasmine V Ware
Karyn D Rode
Jeffrey F Bromaghin
David C Douglas
Ryan R Wilson
Eric V Regehr
Steven C Amstrup
George M Durner
Anthony M Pagano
Jay Olson
Charles T Robbins
Heiko T Jansen
Source
Oecologia. 2017 Feb 28;
Date
Feb-28-2017
Language
English
Publication Type
Article
Abstract
Understanding behavioral responses of species to environmental change is critical to forecasting population-level effects. Although climate change is significantly impacting species' distributions, few studies have examined associated changes in behavior. Polar bear (Ursus maritimus) subpopulations have varied in their near-term responses to sea ice decline. We examined behavioral responses of two adjacent subpopulations to changes in habitat availability during the annual sea ice minimum using activity data. Location and activity sensor data collected from 1989 to 2014 for 202 adult female polar bears in the Southern Beaufort Sea (SB) and Chukchi Sea (CS) subpopulations were used to compare activity in three habitat types varying in prey availability: (1) land; (2) ice over shallow, biologically productive waters; and (3) ice over deeper, less productive waters. Bears varied activity across and within habitats with the highest activity at 50-75% sea ice concentration over shallow waters. On land, SB bears exhibited variable but relatively high activity associated with the use of subsistence-harvested bowhead whale carcasses, whereas CS bears exhibited low activity consistent with minimal feeding. Both subpopulations had fewer observations in their preferred shallow-water sea ice habitats in recent years, corresponding with declines in availability of this substrate. The substantially higher use of marginal habitats by SB bears is an additional mechanism potentially explaining why this subpopulation has experienced negative effects of sea ice loss compared to the still-productive CS subpopulation. Variability in activity among, and within, habitats suggests that bears alter their behavior in response to habitat conditions, presumably in an attempt to balance prey availability with energy costs.
PubMed ID
28247129 View in PubMed
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Heightened Immune System Function in Polar Bears Using Terrestrial Habitats.

https://arctichealth.org/en/permalink/ahliterature298349
Source
Physiol Biochem Zool. 2019 Jan/Feb; 92(1):1-11
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Author
John P Whiteman
Henry J Harlow
George M Durner
Eric V Regehr
Steven C Amstrup
Merav Ben-David
Source
Physiol Biochem Zool. 2019 Jan/Feb; 92(1):1-11
Language
English
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Keywords
Adaptive Immunity
Alaska
Animals
Arctic Regions
Body Weight
C-Reactive Protein - analysis
Climate change
Ecosystem
Female
Ice Cover
Immunity, Innate
Leukocyte Count
Serum globulins
Ursidae - blood - immunology
Abstract
Climate change is altering the distribution of some wildlife species while warming temperatures are facilitating the northward expansion of pathogens, potentially increasing disease risk. Melting of Arctic sea ice is increasingly causing polar bears (Ursus maritimus) of the southern Beaufort Sea (SBS) to spend summer on land, where they may encounter novel pathogens. Here, we tested whether SBS polar bears on shore during summer exhibited greater immune system activity than bears remaining on the sea ice. In addition, we tested whether the type of immune response correlated with body condition, because adaptive responses (slowly developing defenses against specific pathogens) often require less energy than innate responses (rapid defenses not based on pathogen identity). After accounting for body condition, we found that polar bears on shore exhibited higher total white blood cell counts, neutrophils, and monocytes than bears on the ice, suggesting more infections. Lymphocytes, eosinophils, basophils, and globulins did not differ. C-reactive protein, an indicator of inflammation, also did not differ between habitats. Body condition was associated with variables indicative of both innate and adaptive immunity, suggesting that neither response was uniquely limited by energy resources. Our data indicate that as more polar bears spend longer periods of time on shore, they may experience more infections. We encourage continued health monitoring of this species and studies of the long-term fitness consequences from disease.
PubMed ID
30403916 View in PubMed
Less detail

Heightened Immune System Function in Polar Bears Using Terrestrial Habitats.

https://arctichealth.org/en/permalink/ahliterature295793
Source
Physiol Biochem Zool. 2019 Jan/Feb; 92(1):1-11
Publication Type
Journal Article
Author
John P Whiteman
Henry J Harlow
George M Durner
Eric V Regehr
Steven C Amstrup
Merav Ben-David
Source
Physiol Biochem Zool. 2019 Jan/Feb; 92(1):1-11
Language
English
Publication Type
Journal Article
Abstract
Climate change is altering the distribution of some wildlife species while warming temperatures are facilitating the northward expansion of pathogens, potentially increasing disease risk. Melting of Arctic sea ice is increasingly causing polar bears (Ursus maritimus) of the southern Beaufort Sea (SBS) to spend summer on land, where they may encounter novel pathogens. Here, we tested whether SBS polar bears on shore during summer exhibited greater immune system activity than bears remaining on the sea ice. In addition, we tested whether the type of immune response correlated with body condition, because adaptive responses (slowly developing defenses against specific pathogens) often require less energy than innate responses (rapid defenses not based on pathogen identity). After accounting for body condition, we found that polar bears on shore exhibited higher total white blood cell counts, neutrophils, and monocytes than bears on the ice, suggesting more infections. Lymphocytes, eosinophils, basophils, and globulins did not differ. C-reactive protein, an indicator of inflammation, also did not differ between habitats. Body condition was associated with variables indicative of both innate and adaptive immunity, suggesting that neither response was uniquely limited by energy resources. Our data indicate that as more polar bears spend longer periods of time on shore, they may experience more infections. We encourage continued health monitoring of this species and studies of the long-term fitness consequences from disease.
PubMed ID
30403916 View in PubMed
Less detail

Implications of the circumpolar genetic structure of polar bears for their conservation in a rapidly warming arctic.

https://arctichealth.org/en/permalink/ahliterature259415
Source
PLoS One. 2015;10(1):e112021
Publication Type
Article
Date
2015
Author
Elizabeth Peacock
Sarah A Sonsthagen
Martyn E Obbard
Andrei Boltunov
Eric V Regehr
Nikita Ovsyanikov
Jon Aars
Stephen N Atkinson
George K Sage
Andrew G Hope
Eve Zeyl
Lutz Bachmann
Dorothee Ehrich
Kim T Scribner
Steven C Amstrup
Stanislav Belikov
Erik W Born
Andrew E Derocher
Ian Stirling
Mitchell K Taylor
Øystein Wiig
David Paetkau
Sandra L Talbot
Source
PLoS One. 2015;10(1):e112021
Date
2015
Language
English
Publication Type
Article
Abstract
We provide an expansive analysis of polar bear (Ursus maritimus) circumpolar genetic variation during the last two decades of decline in their sea-ice habitat. We sought to evaluate whether their genetic diversity and structure have changed over this period of habitat decline, how their current genetic patterns compare with past patterns, and how genetic demography changed with ancient fluctuations in climate. Characterizing their circumpolar genetic structure using microsatellite data, we defined four clusters that largely correspond to current ecological and oceanographic factors: Eastern Polar Basin, Western Polar Basin, Canadian Archipelago and Southern Canada. We document evidence for recent (ca. last 1-3 generations) directional gene flow from Southern Canada and the Eastern Polar Basin towards the Canadian Archipelago, an area hypothesized to be a future refugium for polar bears as climate-induced habitat decline continues. Our data provide empirical evidence in support of this hypothesis. The direction of current gene flow differs from earlier patterns of gene flow in the Holocene. From analyses of mitochondrial DNA, the Canadian Archipelago cluster and the Barents Sea subpopulation within the Eastern Polar Basin cluster did not show signals of population expansion, suggesting these areas may have served also as past interglacial refugia. Mismatch analyses of mitochondrial DNA data from polar and the paraphyletic brown bear (U. arctos) uncovered offset signals in timing of population expansion between the two species, that are attributed to differential demographic responses to past climate cycling. Mitogenomic structure of polar bears was shallow and developed recently, in contrast to the multiple clades of brown bears. We found no genetic signatures of recent hybridization between the species in our large, circumpolar sample, suggesting that recently observed hybrids represent localized events. Documenting changes in subpopulation connectivity will allow polar nations to proactively adjust conservation actions to continuing decline in sea-ice habitat.
PubMed ID
25562525 View in PubMed
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Increased Land Use by Chukchi Sea Polar Bears in Relation to Changing Sea Ice Conditions.

https://arctichealth.org/en/permalink/ahliterature267864
Source
PLoS One. 2015;10(11):e0142213
Publication Type
Article
Date
2015
Author
Karyn D Rode
Ryan R Wilson
Eric V Regehr
Michelle St Martin
David C Douglas
Jay Olson
Source
PLoS One. 2015;10(11):e0142213
Date
2015
Language
English
Publication Type
Article
Abstract
Recent observations suggest that polar bears (Ursus maritimus) are increasingly using land habitats in some parts of their range, where they have minimal access to their preferred prey, likely in response to loss of their sea ice habitat associated with climatic warming. We used location data from female polar bears fit with satellite radio collars to compare land use patterns in the Chukchi Sea between two periods (1986-1995 and 2008-2013) when substantial summer sea-ice loss occurred. In both time periods, polar bears predominantly occupied sea-ice, although land was used during the summer sea-ice retreat and during the winter for maternal denning. However, the proportion of bears on land for > 7 days between August and October increased between the two periods from 20.0% to 38.9%, and the average duration on land increased by 30 days. The majority of bears that used land in the summer and for denning came to Wrangel and Herald Islands (Russia), highlighting the importance of these northernmost land habitats to Chukchi Sea polar bears. Where bears summered and denned, and how long they spent there, was related to the timing and duration of sea ice retreat. Our results are consistent with other studies supporting increased land use as a common response of polar bears to sea-ice loss. Implications of increased land use for Chukchi Sea polar bears are unclear, because a recent study observed no change in body condition or reproductive indices between the two periods considered here. This result suggests that the ecology of this region may provide a degree of resilience to sea ice loss. However, projections of continued sea ice loss suggest that polar bears in the Chukchi Sea and other parts of the Arctic may increasingly use land habitats in the future, which has the potential to increase nutritional stress and human-polar bear interactions.
PubMed ID
26580809 View in PubMed
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21 records – page 1 of 3.