Polar bears (Ursus maritimus) are one of 4 marine mammal species managed by the U.S. Department of Interior. The USGS Alaska Science Center leads long–term research on polar bears to inform local, state, national and international policy makers regarding conservation of the species and its habitat. Our studies, ongoing since 1985, are focused on population dynamics, health and energetics, distribution and movements, maternal denning, and methods development. The majority of our research focuses on the two polar bear subpopulation’s whose range includes Alaska: the Southern Beaufort Sea subpopulation that ranges between the North Slope of Alaska and western Canada and the Chukchi Sea or Alaska-Chukotka subpopulation that ranges between the northwest coast of Alaska and eastern Russia. The overarching goal of our research is to assess current and projected future responses of polar bears to a rapidly changing Arctic environment.
Return to Ecosystems >> Marine Ecosystems
Population Dynamics
Information on the status and trends of polar bear populations are needed to inform management of polar bears under US laws and international agreements. The USGS maintains a long-term research program focused on the population dynamics of the southern Beaufort Sea polar bear population. In addition, the USGS collaborates with the US Fish and Wildlife Service in population studies in the Chukchi Sea. To estimate both the population size and vital rates, we have used mark-recapture studies relying on physical capture of bears, primarily during the spring. We are currently developing an analytical approach that will allow us to integrate additional types of data (e.g., spatial data, non-invasively collected genetic data) into the modeling process to provide improved assessments of population status. Results of past studies have allowed us to assess the relationships between population vital rates and environmental change, which provides our partners with information needed to inform management decisions.
Health and Energetics
The warming climate has the potential to drive significant changes in the health and energetics of Arctic fauna, particularly those dependent on sea ice habitats like polar bears. An animal’s health and energetic state reflects the interaction between its behavioral choices and the environment. Because of this, measuring changes in health and energetics has potential for revealing important associations between environmental stressors and population dynamics. Research in this focal area is centered on (i) collecting data on a variety of systems that help determine and mediate polar bear health and energetics, and (ii) developing monitoring and surveillance programs for detecting changes in population health over time. Additionally, this work will allow us to develop an understanding of how polar bear populations will respond to a variety of stressors modulated by climate change, including contaminant and pathogen exposures, changes in food web structure and prey accessibility, and changes in spatial distribution.
Distribution and Movements
Polar bears are tied to the sea ice for nearly all of their life cycle functions. Most important of these is foraging, or access to food. Polar bears almost exclusively eat seals, and they are equally as dependent upon the sea for their nutrition as are seals, whales, and other aquatic mammals. Polar bears are not aquatic, however, and their only access to the seals is from the surface of the sea ice. Over the past 25 years, the summer sea ice melt period has lengthened, and summer sea ice cover has declined by over half a million square miles. In winter, there have been dramatic reductions in the amount of old ice, predominantly in the western Arctic. This loss of stable old ice has catalyzed additional losses of sea ice cover each summer because the thinner younger ice is more easily melted during the recent warmer summers. Research in this focal area seeks to develop a better understanding of how changes in the distribution and characteristics of sea ice habitat are likely to affect polar bear fitness, distribution, and interactions with people. If we know how polar bears respond to changes in ice quantity and quality, we will be able to predict how forecasted changes in the ice may affect future polar bear populations. This will give managers the best chance of adapting strategies to assure the long-term persistence of polar bears in a changing ice environment.
Maternal Denning
Pregnant polar bears enter maternity dens in October or early November, give birth to cubs in December or early January, and exit dens in March or early April. Historically, most polar bears from the Southern Beaufort Sea population constructed maternity dens on the sea ice. However, over the last three decades, as sea ice has become thinner and more prone to fragmentation, there has been a landward shift in the distribution of dens. Based on data collected from radio-tagged adult female bears, maternal denning now occurs at relatively high densities along the central and eastern Arctic coastal plain of Alaska. The availability of denning habitat― mediated by landscape features that facilitate the formation of snow drifts― appears to increase in the eastern portion of the Alaska coastal plain. In the Chukchi Sea, polar bears historically denned primarily on land in both Russia and the Alaska. In recent years as sea ice extent has retreated further north in the fall, Chukchi Sea polar bears have shifted land-based denning northward primarily on Wrangel and Herald Islands in Russia and rarely on the Alaskan coast. Identifying factors influencing the distribution of dens and denning duration will allow us to better monitor reproductive success and mitigate the potential for disturbance of denned bears from anthropogenic activities.
Below are other science projects associated with this project.
Q&A: Polar Bears and Zoos
Polar Bear Media/Contacts
Polar Bear Maternal Denning
Polar Bear Population Dynamics
Distribution and Movements of Polar Bears
Health and Energetics of Polar Bears
Below are data or web applications associated with this project.
Polar Bear Continuous Time-Correlated Random Walk (CTCRW) Location Data Derived from Satellite Location Data, Chukchi and Beaufort Seas, July-November 1985-2017
Data Used to Assess the Acute Physiological Response of Polar Bears to Helicopter Capture
Polar Bear Fall Coastal Survey Data from the Southern Beaufort Sea of Alaska, 2010-2013
Mapping data of Polar Bear (Ursus maritimus) maternal den habitat, Arctic Coastal Plain, Alaska
Pathogen and Contaminant Exposure Data from Southern Beaufort Sea Polar Bears, 2007-2014
Polar Bear Continuous Time-Correlated Random Walk (CTCRW) Location Data Derived from Satellite Location Data, Southern Beaufort Sea, 1986-2016
Innate Immunity and Stress and Reproductive Hormone Metrics for Southern Beaufort Sea Polar Bears, 2013-2015
Protein and Fat Consumption of Zoo Polar Bears in 14-day Ad Libitum Trials, 2019-2020
Denning Phenology, Den Substrate, and Reproductive Success of Female Polar Bears (Ursus maritimus) in the southern Beaufort Sea 1986-2013 and the Chukchi Sea 1987-1994
Cortisol Concentration Data from Polar Bear (Ursus maritimus) Hair Collected in the Bering, Chukchi, and Beaufort seas, Alaska, 1983-1989, 2004-2006, and 2008-2016
Carbon and Nitrogen Isotope Concentrations in Polar Bear Hair and Prey from the Alaska Beaufort and Chukchi Seas, 1978-2019
Fatty Acid Composition of Polar Bear Adipose Tissue and Ringed and Bearded Seal Blubber Collected in the Chukchi Sea, 2008-2017
Below are publications associated with this project.
High winds and melting sea ice trigger landward movement in a polar bear population of concern
Efficacy of bear spray as a deterrent against polar bears
Observed and forecasted changes in land use by polar bears in the Beaufort and Chukchi Seas, 1985–2040
Diet energy density estimated from isotopes in predator hair associated with survival, habitat, and population dynamics
Modeling the spatial and temporal dynamics of land-based polar bear denning in Alaska
Comparisons of Coupled Model Intercomparison Project Phase 5 (CMIP5) and Coupled Model Intercomparison Project Phase 6 (CMIP6) sea-ice projections in polar bear (Ursus maritimus) ecoregions during the 21st century
Using in situ/ex situ research collaborations to support polar bear conservation
Evaluating the efficacy of aerial infrared surveys to detect artificial polar bear dens
Intrapopulation differences in polar bear movement and step selection patterns
The role of satellite telemetry data in 21st century conservation of polar bears (Ursus maritimus)
Summer/fall diet and macronutrient assimilation in an Arctic predator
Below are news stories associated with this project.
Below are partners associated with this project.
- Overview
Polar bears (Ursus maritimus) are one of 4 marine mammal species managed by the U.S. Department of Interior. The USGS Alaska Science Center leads long–term research on polar bears to inform local, state, national and international policy makers regarding conservation of the species and its habitat. Our studies, ongoing since 1985, are focused on population dynamics, health and energetics, distribution and movements, maternal denning, and methods development. The majority of our research focuses on the two polar bear subpopulation’s whose range includes Alaska: the Southern Beaufort Sea subpopulation that ranges between the North Slope of Alaska and western Canada and the Chukchi Sea or Alaska-Chukotka subpopulation that ranges between the northwest coast of Alaska and eastern Russia. The overarching goal of our research is to assess current and projected future responses of polar bears to a rapidly changing Arctic environment.
Return to Ecosystems >> Marine Ecosystems
Population Dynamics
Polar bear family at a whale bone pile near Kaktovik, Alaska.(Public domain.) Information on the status and trends of polar bear populations are needed to inform management of polar bears under US laws and international agreements. The USGS maintains a long-term research program focused on the population dynamics of the southern Beaufort Sea polar bear population. In addition, the USGS collaborates with the US Fish and Wildlife Service in population studies in the Chukchi Sea. To estimate both the population size and vital rates, we have used mark-recapture studies relying on physical capture of bears, primarily during the spring. We are currently developing an analytical approach that will allow us to integrate additional types of data (e.g., spatial data, non-invasively collected genetic data) into the modeling process to provide improved assessments of population status. Results of past studies have allowed us to assess the relationships between population vital rates and environmental change, which provides our partners with information needed to inform management decisions.
Health and Energetics
The warming climate has the potential to drive significant changes in the health and energetics of Arctic fauna, particularly those dependent on sea ice habitats like polar bears. An animal’s health and energetic state reflects the interaction between its behavioral choices and the environment. Because of this, measuring changes in health and energetics has potential for revealing important associations between environmental stressors and population dynamics. Research in this focal area is centered on (i) collecting data on a variety of systems that help determine and mediate polar bear health and energetics, and (ii) developing monitoring and surveillance programs for detecting changes in population health over time. Additionally, this work will allow us to develop an understanding of how polar bear populations will respond to a variety of stressors modulated by climate change, including contaminant and pathogen exposures, changes in food web structure and prey accessibility, and changes in spatial distribution.
Distribution and Movements
A polar bear walks across rubble ice in the Alaska portion of the southern Beaufort Sea. (Credit: Mike Lockhart, USGS. Public domain.) Polar bears are tied to the sea ice for nearly all of their life cycle functions. Most important of these is foraging, or access to food. Polar bears almost exclusively eat seals, and they are equally as dependent upon the sea for their nutrition as are seals, whales, and other aquatic mammals. Polar bears are not aquatic, however, and their only access to the seals is from the surface of the sea ice. Over the past 25 years, the summer sea ice melt period has lengthened, and summer sea ice cover has declined by over half a million square miles. In winter, there have been dramatic reductions in the amount of old ice, predominantly in the western Arctic. This loss of stable old ice has catalyzed additional losses of sea ice cover each summer because the thinner younger ice is more easily melted during the recent warmer summers. Research in this focal area seeks to develop a better understanding of how changes in the distribution and characteristics of sea ice habitat are likely to affect polar bear fitness, distribution, and interactions with people. If we know how polar bears respond to changes in ice quantity and quality, we will be able to predict how forecasted changes in the ice may affect future polar bear populations. This will give managers the best chance of adapting strategies to assure the long-term persistence of polar bears in a changing ice environment.
Maternal Denning
Pregnant polar bears enter maternity dens in October or early November, give birth to cubs in December or early January, and exit dens in March or early April. Historically, most polar bears from the Southern Beaufort Sea population constructed maternity dens on the sea ice. However, over the last three decades, as sea ice has become thinner and more prone to fragmentation, there has been a landward shift in the distribution of dens. Based on data collected from radio-tagged adult female bears, maternal denning now occurs at relatively high densities along the central and eastern Arctic coastal plain of Alaska. The availability of denning habitat― mediated by landscape features that facilitate the formation of snow drifts― appears to increase in the eastern portion of the Alaska coastal plain. In the Chukchi Sea, polar bears historically denned primarily on land in both Russia and the Alaska. In recent years as sea ice extent has retreated further north in the fall, Chukchi Sea polar bears have shifted land-based denning northward primarily on Wrangel and Herald Islands in Russia and rarely on the Alaskan coast. Identifying factors influencing the distribution of dens and denning duration will allow us to better monitor reproductive success and mitigate the potential for disturbance of denned bears from anthropogenic activities.
- Science
Below are other science projects associated with this project.
Q&A: Polar Bears and Zoos
Polar bears are found throughout the circumpolar Arctic and roam across miles of sea ice and land. They prefer to eat blubber, especially from seals that are also found on the sea ice. However, the sea ice habitat of polar bears is changing rapidly with substantial recent declines in the extent of sea ice in the Arctic. These changes are leading polar bears to spend more time on land in some areas...Polar Bear Media/Contacts
If you have questions about research or media inquiries regarding the USGS Alaska Science Center please contact Yvette Gillies.Polar Bear Maternal Denning
Pregnant polar bears enter maternity dens in October/November, give birth to cubs in December/January, and exit dens in March/April. Historically, most polar bears from the Southern Beaufort Sea (SBS) population constructed maternity dens on the sea ice. Over the last three decades, as sea ice has become thinner and prone to fragmentation, there has been a landward shift in the distribution of...Polar Bear Population Dynamics
Information on the status and trends of polar bear populations are needed to inform management of polar bears under US laws and international agreements. The USGS maintains a long-term research program focused on the population dynamics of the southern Beaufort Sea polar bear population. In addition, the USGS collaborates with the US Fish and Wildlife Service in population studies in the Chukchi...Distribution and Movements of Polar Bears
Polar bears are tied to the sea ice for nearly all of their life cycle functions. Most important of these is foraging, or access to food. Polar bears almost exclusively eat seals, and they are equally as dependent upon the sea for their nutrition as are seals, whales, and other aquatic mammals. Polar bears are not aquatic, however, and their only access to the seals is from the surface of the sea...Health and Energetics of Polar Bears
Research in this focal area is centered on (i) collecting data on a variety of systems that help determine and mediate polar bear health and energetics, and (ii) developing monitoring and surveillance programs for detecting changes in population health over time. Additionally, this work will allow us to develop an understanding of how polar bear populations will respond to a variety of stressors... - Data
Below are data or web applications associated with this project.
Filter Total Items: 32Polar Bear Continuous Time-Correlated Random Walk (CTCRW) Location Data Derived from Satellite Location Data, Chukchi and Beaufort Seas, July-November 1985-2017
his dataset consists of one table with estimated locations of adult female polar bears during July-November 1985-2017, used for quantifying changes in summer land use over time. Locations were estimated with a Continuous Time-Correlated Random Walk (CTCRW) model fit to satellite tracking from radio-collared adult female polar bears. All bears included in this data set were captured and instrumenteData Used to Assess the Acute Physiological Response of Polar Bears to Helicopter Capture
This dataset is in five tables with data from ecophysiological studies of free-ranging polar bears of the Southern Beaufort Sea subpopulation. They were equipped with high-resolution activity sensors, body temperature loggers, and GPS satellite-telemetry collars, to compare physiological state and activity of bears during natural behavior with that experienced by bears during helicopter recapturePolar Bear Fall Coastal Survey Data from the Southern Beaufort Sea of Alaska, 2010-2013
This data set is one table with observations of polar bears located during aerial surveys along the coast and barrier islands of the southern Beaufort Seas during fall, 2010-2013. Survey flights were conducted using A-Star B2 and Bell 206 helicopters at an average altitude of 300 feet AGL and an average speed of 50 miles per hour. Survey crews searched for polar bears using coastal and inland tranMapping data of Polar Bear (Ursus maritimus) maternal den habitat, Arctic Coastal Plain, Alaska
These are geospatial data that characterize the distribution of polar bear denning habitat on the National Petroleum Reserve-Alaska (NPR-A), the 1002 Area of the Arctic National Wildlife Refuge and the coastal plain of northern Alaska between the Colville River and the Alaska/Canada border.Pathogen and Contaminant Exposure Data from Southern Beaufort Sea Polar Bears, 2007-2014
These were data collected from polar bears from the Southern Beaufort Sea during the spring between 2007 and 2014. Data include individual ID, capture date, sex and age class, whether individuals visited bowhead whale carrion sites, exposure status relative to five pathogens, and concentrations of certain persistent organic pollutants.Polar Bear Continuous Time-Correlated Random Walk (CTCRW) Location Data Derived from Satellite Location Data, Southern Beaufort Sea, 1986-2016
This dataset consists of one table with predicted locations of adult female polar bears. Locations were derived by a Continuous Time-Correlated Random Walk (CTCRW) model using satellite tracking radio-collared adult female polar bears captured and instrumented in the southern Beaufort Sea, 1986–2016.Innate Immunity and Stress and Reproductive Hormone Metrics for Southern Beaufort Sea Polar Bears, 2013-2015
These were data collected from polar bears from the Southern Beaufort Sea during the spring between 2013 and 2015. Data include individual identification, demographic characteristics, year, status for the current and prior year regarding use of land, concentrations of stress response and reproductive hormones, blood-based biomarker measures indicative of fasting, body mass index, and body conditioProtein and Fat Consumption of Zoo Polar Bears in 14-day Ad Libitum Trials, 2019-2020
This is a single table containing measures of the amount of fat and meat consumed by 4 adult female and 5 adult male polar bears in U.S. zoos when provided both food sources ad libitum for 12-14 days. Trial length was intended to be 14 days, but trial dietary items ran out for two bears prior to the end of the trial (i.e., at 12 and 13 days instead of 14 days). The data set includes the weight ofDenning Phenology, Den Substrate, and Reproductive Success of Female Polar Bears (Ursus maritimus) in the southern Beaufort Sea 1986-2013 and the Chukchi Sea 1987-1994
These data represent estimates of den entrance and exit dates for female polar bears in the southern Beaufort and Chukchi Seas based on temperature sensor data obtained from satellite collars. An algorithm described in Olson et al. (2017) was used to determine whether the female entered a den and further analyses using temperature data as described in Olson et al. (2017) were used to assess den enCortisol Concentration Data from Polar Bear (Ursus maritimus) Hair Collected in the Bering, Chukchi, and Beaufort seas, Alaska, 1983-1989, 2004-2006, and 2008-2016
This data release contains one table which includes the concentration of cortisol from polar bear (Ursus maritimus) hair and morphometric data from some of the captured bears. We assayed concentration of cortisol in hair (HCC) from polar bears captured in the Alaska Beaufort, Bering and Chukchi seas during 1983-1989 and 2004-2016. Fields include the individual polar bear identifier (bearID), the dCarbon and Nitrogen Isotope Concentrations in Polar Bear Hair and Prey from the Alaska Beaufort and Chukchi Seas, 1978-2019
This dataset includes carbon and nitrogen isotope concentrations measured in polar bear hair and marine mammal prey samples collected 1978-2017 in the Beaufort and Chukchi Seas. Marine mammal prey samples were collected opportunistically either from polar bear seal kill sites or from marine mammals harvested by Native hunters. Hair was collected from polar bears captured on the sea ice or land inFatty Acid Composition of Polar Bear Adipose Tissue and Ringed and Bearded Seal Blubber Collected in the Chukchi Sea, 2008-2017
These data are the fatty acid compositions (in %) of adipose tissue samples collected from polar bears and of blubber samples collected from ringed and bearded seal killed by polar bears in the Chukchi Sea, 2008-2017. The dataset includes sex, age, and age class of the bears that were sampled. The data are provided as % of each fatty acid identified via nomenclature that describes the structure of - Multimedia
- Publications
Below are publications associated with this project.
Filter Total Items: 83High winds and melting sea ice trigger landward movement in a polar bear population of concern
Some animal species are responding to climate change by altering the timing of events like mating and migration. Such behavioral plasticity can be adaptive, but it is not always. Polar bears (Ursus maritimus) from the southern Beaufort Sea subpopulation have mostly remained on ice year-round, but as the climate warms and summer sea ice declines, a growing proportion of the subpopulation is summeriEfficacy of bear spray as a deterrent against polar bears
Although there have been few attempts to systematically analyze information on the use of deterrents on polar bears (Ursus maritimus), understanding their effectiveness in mitigating human-polar bear conflicts is critical to ensuring both human safety and polar bear conservation. To fill this knowledge gap, we analyzed 19 incidents involving the use of bear spray on free-ranging polar bears from 1Observed and forecasted changes in land use by polar bears in the Beaufort and Chukchi Seas, 1985–2040
Monitoring changes in the distribution of large carnivores is important for managing human safety and supporting conservation. Throughout much of their range, polar bears (Ursus maritimus) are increasingly using terrestrial habitats in response to Arctic sea ice decline. Their increased presence in coastal areas has implications for bear-human conflict, inter-species interactions, and polar bear hDiet energy density estimated from isotopes in predator hair associated with survival, habitat, and population dynamics
Sea ice loss is fundamentally altering the Arctic marine environment. Yet there is a paucity of data on the adaptability of food webs to ecosystem change, including predator-prey interactions. Polar bears (Ursus maritimus) are an important subsistence resource for Indigenous people and an apex predator that relies entirely on the under-ice food web to meet their energy needs. Here, we assessed wheModeling the spatial and temporal dynamics of land-based polar bear denning in Alaska
Although polar bears (Ursus maritimus) of the Southern Beaufort Sea (SBS) subpopulation have commonly created maternal dens on sea ice in the past, maternal dens on land have become increasingly prevalent as sea ice declines. This trend creates conditions for increased human–bear interactions associated with local communities and industrial activity. Maternal denning is a vulnerable period in theComparisons of Coupled Model Intercomparison Project Phase 5 (CMIP5) and Coupled Model Intercomparison Project Phase 6 (CMIP6) sea-ice projections in polar bear (Ursus maritimus) ecoregions during the 21st century
Climate model projections are commonly used to assess potential impacts of global warming on a breadth of social, economic, and environmental topics. Modeling centers throughout the world coordinate to apply a consistent suite of radiative forcing experiments so that all model outputs can be collectively analyzed and compared. Three generations of model outputs have been produced and made availablUsing in situ/ex situ research collaborations to support polar bear conservation
A warming Arctic threatens the long-term persistence of polar bears (Ursus maritimus) in the wild. Historically, little collaboration existed between the in situ and ex situ polar bear scientific communities. However, for the past decade, zoo professionals, government agencies, and non-governmental organizations (NGO’s) have partnered to leverage resources and expertise with the goal of addressingEvaluating the efficacy of aerial infrared surveys to detect artificial polar bear dens
The need to balance economic development with impacts to Arctic wildlife has been a prominent subject since petroleum exploration began on the North Slope of Alaska, USA, in the late 1950s. The North Slope region includes polar bears (Ursus maritimus) of the southern Beaufort Sea subpopulation, which has experienced a long-term decline in abundance. Pregnant polar bears dig dens in snow drifts durIntrapopulation differences in polar bear movement and step selection patterns
BackgroundThe spatial ecology of individuals often varies within a population or species. Identifying how individuals in different classes interact with their environment can lead to a better understanding of population responses to human activities and environmental change and improve population estimates. Most inferences about polar bear (Ursus maritimus) spatial ecology are based on data from aThe role of satellite telemetry data in 21st century conservation of polar bears (Ursus maritimus)
Satellite telemetry (ST) has played a critical role in the management and conservation of polar bears (Ursus maritimus) over the last 50 years. ST data provide biological information relevant to subpopulation delineation, movements, habitat use, maternal denning, health, human-bear interactions, and accurate estimates of vital rates and abundance. Given that polar bears are distributed at low densSummer/fall diet and macronutrient assimilation in an Arctic predator
Free-ranging predator diet estimation is commonly achieved by applying molecular-based tracers because direct observation is not logistically feasible or robust. However, tracers typically do not represent all dietary macronutrients, which likely obscures resource use as prey proximate composition varies and tissue consumption can be specific. For example, polar bears (Ursus maritimus) preferentia - News
Below are news stories associated with this project.
Filter Total Items: 13 - Partners
Below are partners associated with this project.