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 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
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
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
Serum Urea and Creatinine Levels of Spring-Caught Polar Bears (Ursus maritimus) in the Southern Beaufort and Chukchi Seas
Multistate capture and search data from the southern Beaufort Sea polar bear population in Alaska, 2001-2016
Polar Bear Distribution and Habitat Resource Selection Data, Beaufort and Chukchi Seas, 1985-2016
Data from a Circumpolar Survey on Recreational Activities in Polar Bear Habitat, 2017-2018
Below are publications associated with this project.
Diet-driven mercury contamination is associated with polar bear gut microbiota
New insights into dietary management of polar bears (Ursus maritimus) and brown bears (U. arctos)
Effects of sea ice decline and summer land use on polar bear home range size in the Beaufort Sea
Iñupiaq knowledge of polar bears (Ursus maritimus) in the southern Beaufort Sea, Alaska
Survival and abundance of polar bears in Alaska’s Beaufort Sea, 2001–2016
Energetic and health effects of protein overconsumption constrain dietary adaptation in an apex predator
Measuring adrenal and reproductive hormones in hair from southern Beaufort Sea polar bears (Ursus maritimus)
Seal body condition and atmospheric circulation patterns influence polar bear body condition, recruitment, and feeding ecology in the Chukchi Sea
How Is climate change affecting polar bears and giant pandas?
Polar Bear (Ursus maritimus)
Analyses on subpopulation abundance and annual number of maternal dens for the U.S. Fish and Wildlife Service on polar bears (Ursus maritimus) in the southern Beaufort Sea, Alaska
Erratum: Seismic survey design and effects on maternal polar bear dens
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.
Polar 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.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 conditioDenning 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 ofSerum Urea and Creatinine Levels of Spring-Caught Polar Bears (Ursus maritimus) in the Southern Beaufort and Chukchi Seas
These data are serum urea nitrogen and creatinine levels for polar bears captured in the southern Beaufort Sea 1983-2016 and the Chukchi Sea 1987-1993 and 2008-2017. The dataset includes relevant information about the bears that were captured including the latitude and longitude of their capture location, capture date, age class and sex, the age and number of cubs accompanying an adult female, andMultistate capture and search data from the southern Beaufort Sea polar bear population in Alaska, 2001-2016
This data release contains two tables of information on polar bear distributions in the southern Beaufort Sea during spring, from 2001 to 2016. One table provides location (classified into 5 broad regions) of individual bears during the spring. The other table presents the aerial search effort by year and area.Polar Bear Distribution and Habitat Resource Selection Data, Beaufort and Chukchi Seas, 1985-2016
These data from satellite radio-collared adult female polar bears captured in the southern Beaufort Sea, 1985-2016 were used for testing the regional, seasonal and decadal efficacy of retrospective polar bear resource selection functions (RSF) developed for the Arctic basin and its peripheral seas (see Durner et al. 2009). The data includes the following: 1) a csv file of locations used to build aData from a Circumpolar Survey on Recreational Activities in Polar Bear Habitat, 2017-2018
These data are the responses of researchers, managers, community members, and tour guides who live or work in polar bear habitats anywhere within their range to inquiries about the types, frequency, and potential impacts of recreational activities. Respondents answered a series of questions on their background and experience with polar bears and the geographic area in which they are familiar. Resp - Multimedia
- Publications
Below are publications associated with this project.
Filter Total Items: 68Diet-driven mercury contamination is associated with polar bear gut microbiota
The gut microbiota may modulate the disposition and toxicity of environmental contaminants within a host but, conversely, contaminants may also impact gut bacteria. Such contaminant-gut microbial connections, which could lead to alteration of host health, remain poorly known and are rarely studied in free-ranging wildlife. The polar bear (Ursus maritimus) is a long-lived, wide-ranging apex predatoNew insights into dietary management of polar bears (Ursus maritimus) and brown bears (U. arctos)
Although polar bears (Ursus maritimus) and brown bears (U. arctos) have been exhibited in zoological gardens for centuries, little is known about their nutritional needs. Multiple recent studies on both wild and captive polar bears and brown bears have found that they voluntarily select dietary macronutrient proportions resulting in much lower dietary protein and higher fat or digestible carbohydrEffects of sea ice decline and summer land use on polar bear home range size in the Beaufort Sea
Animals responding to habitat loss and fragmentation may increase their home ranges to offset declines in localized resources or they may decrease their home ranges and switch to alternative resources. In many regions of the Arctic, polar bears (Ursus maritimus) exhibit some of the largest home ranges of any quadrupedal mammal. Polar bears are presently experiencing a rapid decline in Arctic sea iIñupiaq knowledge of polar bears (Ursus maritimus) in the southern Beaufort Sea, Alaska
Successful wildlife management depends upon coordination and consultation with local communities. However, much of the research used to inform management is often derived solely from data collected directly from wildlife. Indigenous people living in the Arctic have a close connection to their environment, which provides unique opportunities to observe their environment and the ecology of Arctic spSurvival and abundance of polar bears in Alaska’s Beaufort Sea, 2001–2016
The Arctic Ocean is undergoing rapid transformation toward a seasonally ice-free ecosystem. As ice-adapted apex predators, polar bears (Ursus maritimus) are challenged to cope with ongoing habitat degradation and changes in their prey base driven by food-web response to climate warming. Knowledge of polar bear response to environmental change is necessary to understand ecosystem dynamics and inforEnergetic and health effects of protein overconsumption constrain dietary adaptation in an apex predator
Studies of predator feeding ecology commonly focus on energy intake. However, captive predators have been documented to selectively feed to optimize macronutrient intake. As many apex predators experience environmental changes that affect prey availability, limitations on selective feeding can affect energetics and health. We estimated the protein:fat ratio of diets consumed by wild polar bears usMeasuring adrenal and reproductive hormones in hair from southern Beaufort Sea polar bears (Ursus maritimus)
Polar bears (Ursus maritimus) use sea ice to access marine mammal prey. In Alaska’s Southern Beaufort Sea, the declining availability of sea ice habitat in summer and fall has reduced opportunities for polar bears to routinely hunt on the ice for seals, their primary prey. This reduced access to prey may result in physiological stress with subsequent potential consequences to reproductive functionSeal body condition and atmospheric circulation patterns influence polar bear body condition, recruitment, and feeding ecology in the Chukchi Sea
Polar bears (Ursus maritimus) are experiencing loss of sea ice habitats used to access their marine mammal prey. Simultaneously, ocean warming is changing ecosystems that support marine mammal populations. The interactive effects of sea ice and prey are not well understood yet may explain spatial‐temporal variation in the response of polar bears to sea ice loss. Here, we examined the potential comHow Is climate change affecting polar bears and giant pandas?
Anthropogenic greenhouse gas emissions are the primary cause of climate change and an estimated increase of 3.7 to 4.8 °C is predicted by the year 2100 if emissions continue at current levels. Polar bears (Ursus maritimus) and giant pandas (Ailuropoda melanoleuca) provide an interesting comparison study of the impact of climate change on bear species. While polar bears and giant pandas are arguablPolar Bear (Ursus maritimus)
This chapter comprises the following sections: names, taxonomy, subspecies and distribution, descriptive notes, habitat, movements and home range, activity patterns, feeding ecology, reproduction and growth, behavior, parasites and diseases, status in the wild, and status in captivity.Analyses on subpopulation abundance and annual number of maternal dens for the U.S. Fish and Wildlife Service on polar bears (Ursus maritimus) in the southern Beaufort Sea, Alaska
The long-term persistence of polar bears (Ursus maritimus) is threatened by sea-ice loss due to climate change, which is concurrently providing an opportunity in the Arctic for increased anthropogenic activities including natural resource extraction. Mitigating the risk of those activities, which can adversely affect the population dynamics of the southern Beaufort Sea (SBS) subpopulation, is an eErratum: Seismic survey design and effects on maternal polar bear dens
Since the publication of this manuscript, readers have noted two errors in our analysis. The first is that we inadvertently stated that the forward looking infrared (FLIR) survey simulations only represented a single FLIR survey. In reality, the analysis assumed two independent FLIR surveys occurred prior to simulated seismic activity occurring. To evaluate the results for a single FLIR survey, - News
Below are news stories associated with this project.
- Partners
Below are partners associated with this project.