The Interagency Grizzly Bear Study Team (IGBST) is an interdisciplinary group of scientists and biologists responsible for long-term monitoring and research efforts on grizzly bears in the Greater Yellowstone Ecosystem (GYE). The team was formed by the Department of the Interior (DOI) in 1973 as a direct result of controversy surrounding the closure of open pit garbage dumps within Yellowstone National Park during 1968-72. IGBST members are representatives from the U.S. Geological Survey, National Park Service, U.S. Fish and Wildlife Service, U.S. Forest Service, the Eastern Shoshone and Northern Arapaho Tribal Fish and Game Department, and the States of Idaho, Montana, and Wyoming. This interagency approach ensures consistency in data collection and allows for combining limited resources to address information needs throughout the GYE.
The IGBST Leader serves as a technical and science advisor to the Interagency Grizzly Bear Committee and its Yellowstone Ecosystem Subcommittee, but is not a voting member of the committees.
The main objectives of the team are to 1) monitor the status and trend of the grizzly bear population in the GYE and 2) determine patterns of habitat use by bears and the relationship of land management activities to the welfare of the bear population. To meet these objectives, the team focuses on three main research areas.
Unique Females with Cubs-of-the-Year
Adult females are the most important demographic segment of the grizzly bear populations because they are the reproductive engine. Adult females with cubs-of-the-year (cubs) are the most easily and reliably recognized cohort of grizzly bear populations. Consequently females with cubs are a major focus of IGBST’s monitoring program in the Greater Yellowstone Ecosystem (GYE). Tracking trend for this segment of the population is generally representative of the trend for entire population. Thus, if we observe growth in numbers of female with cubs, we can be reasonably sure the entire population is growing. Efforts by IGBST to document the abundance and distribution of females with cubs began in 1973 and have improved over time by implementing standardized protocols and new statistical procedures. During the past 10 years (2006-2015), IGBST has estimated an average of 56 unique females with cubs annually. When combined with other data, these estimates serve as the basis for estimating total population size. Estimates of total population size are used by IGBST to evaluate annual mortality and to assess whether mortality is sustainable. Sustainable mortality establishes a limit on the number of grizzly deaths that can occur given population objectives. Information from these studies is crucial to evaluate trends in the grizzly bear population and assess the long-term health of the population.
Radio-Collaring Bears
IGBST began radiocollaring grizzly bears in the Greater Yellowstone Ecosystem (GYE) in 1975. Since then, we have radio-monitored over 830 individuals for varying durations, typically for 2 to 3 years. Over 100 individuals have been monitored during more than 5 different years. Our monitoring program changed in 1986 based on directions from the Interagency Grizzly Bear Committee’s Population Task Force. They recommended we maintain and monitor a minimum of 25 radio-collared adult females annually. We also use telemetry to monitor a representative sample of adult males. Data collected from radio-marked bears provide information necessary for tracking key population parameters. By observing radio-collared bears, we document age of first reproduction, average litter size, cub and yearling survival, how often a female produces a litter, and causes of mortality. These data allow us to estimate survival among different sex and age classes of bears. Collectively, this is referred to as “known-fate monitoring”. In conjunction with other estimates (i.e., number of females with cubs, annual mortality), this information is used estimate population size and evaluate sustainable mortality. Location information obtained from collared bears also provides reliable data that helps resource managers focus their activities toward landscape issues that impact grizzly bears in the GYE.
All research animals are handled by following the specific requirements of USGS Animal Care and Use policies.
Whitebark Pine Monitoring
Whitebark pine seeds are a high-calorie food resource available to grizzly bears during late summer and fall. Because whitebark pine is a masting species, cone production is variable, with good crops every 2 to 3 years. Whitebark pine seeds are high in fats and proteins and, when available, allow grizzly bears to build up fat reserves during fall in preparation for hibernation. Grizzly bears harvest these cones by raiding seed caches of red squirrels (middens). Since 1980, we have annually monitored whitebark pine cone production throughout the Greater Yellowstone Ecosystem (GYE) using surveys of established transects. Our data show that mature, cone-producing whitebark pine trees in the GYE have experienced substantial mortality, primarily due to a mountain pine beetle outbreak that started in the early 2000s, but also from white pine blister rust, and fire. IGBST research shows that grizzly bears are adapting to these changes by shifting their diets (see Food Synthesis Report). However, we will continue to monitor this food resource because bears still make extensive use of it in years of good cone production. Click here for IGBST Whitebark Pine Cone Production Annual Summaries.
FOR INFORMATION ABOUT GRIZZLY BEAR MORTALITY, SEE BOTTOM OF PAGE (below "Reports" section).
Direct Links:
Grizzly Bear Mortality Information (See "Grizzly Bear Mortality Information" near bottom of page)
Bear Caused Human Fatalities in the GYE, 1892 - Present
IGBST Grizzly Bear Food Synthesis Report
IGBST Whitebark Pine Cone Production Annual Summaries
Animated image showing grizzly bear range expansion in GYE: 1990-2020
Reports:
A Reassessment of Chao2 Estimates for Population Monitoring of Grizzly
IGBST Demographic Workshop Report
GRIZZLY BEAR MORTALITY INFORMATION:
Identifying the locations and causes of grizzly bear mortality is a key component in understanding the dynamics of this population. About 85% of all documented bear mortalities are human-caused. Tracking human-caused bear deaths helps define patterns and trends that can direct management programs designed to reduce bear mortality.
1) Documented known and probable grizzly bear mortalities in the Greater Yellowstone Ecosystem for 2022 can be found in a provisional USGS data release that is updated as grizzly bear mortalities are reported by IGBST member agencies throughout the year. Go to “Attached Files” and download the “GB_Mortality_2022 csv” file, which contains a table with all reported mortalities for the current year.
Important notice: Because the current year’s grizzly bear mortality data are continuously updated and thus subject to revision, they are considered preliminary data by the USGS. Therefore, if these data are used for any purpose, please refer to them as preliminary data (see full data disclaimer under the “Summary” section of the provisional data release). At the end of the calendar year, these data will be compiled, undergo additional review, and added to the existing data release listed below, which contains documented mortality data compiled by the IGBST since 2015. Once the current year’s data are added to the existing data release, they are no longer considered provisional, which will be reflected on this website.
2) Documented known and probable grizzly bear mortalities in the Greater Yellowstone Ecosystem during 2015-2021 can be found in a USGS data release.
3) 2009-2014 grizzly bear mortality tables can be found in IGBST Annual Reports of the same years.
Below are other science projects associated with this project.
IGBST Annual Reports
IGBST Grizzly Bear Food Synthesis Report
IGBST Whitebark Pine Cone Production Annual Summaries
History of the IGBST
The IGBST has been capturing and radiocollaring grizzly bears since 1975. Data collected from marked bears provide the information necessary for tracking key population parameters. This gallery shows the process by which we capture and collar grizzly bears for research purposes. All research animals are handled by following the specific requirements of USGS Animal Care and Use policies.
Animated image showing grizzly bear range expansion in GYE: 1990-2020
Sequential estimates of occupied ranges for grizzly bears in the Greater Yellowstone Ecosystem during 1990–2020. Range extents are based on methods described in Bjornlie et al. (2014).
IGBST Complete Publications 1974 - 2020
Physiological consequences of consuming low-energy foods: Herbivory coincides with a stress response in Yellowstone bears.
Quantifying energetic costs and defining energy landscapes experienced by grizzly bears
Mammal species composition and habitat associations in a commercial forest and mixed-plantation landscape
Thermal constraints on energy balance, behaviour and spatial distribution of grizzly bears
An evaluation of noninvasive sampling techniques for Malayan sun bears
Brown Bear (Ursus arctos; North America)
Ecological and social dimensions of sloth bear conservation in Sri Lanka
Whitebark pine cone production - 2020
Potential for recreational restrictions to reduce grizzly bear–caused human injuries
Primarily resident grizzly bears respond to late-season elk harvest
Yellowstone grizzly bear investigations: Annual report of the Interagency Grizzly Bear Study Team 2018
Current grizzly bear mortality tables are located on the Interagency Grizzly Bear Study Team main page (Overview tab) under the "Grizzly Bear Mortality Information" section
IGBST Interactive Map
This map shows the overlapping boundaries of significant ecological and land management areas in the Greater Yellowstone Ecosystem used by the IGBST to show grizzly bear distribution and occupancy. Click on each boundary for more information.
IGBST GIS Data Download
This links to the IGBST mapping boundary layers related to the teams research and monitoring that is available at this time. Resources include KMZ files, Metadata files, and Shape files.
IGBC Food Storage Regulation Map
Food Storage Regulations in Grizzly Bear Recovery Areas: If you are going to any of the Grizzly Bear Recovery Areas to camp, hunt or hike you may be required to keep your food, garbage and livestock feed in special bear-resistant containers. Once you have chosen your destination, you can find and read these “Food Storage Regulations” by clicking on the links listed on this page developed by IGBC.
Below are news stories associated with this project.
In a changing ecosystem, Yellowstone grizzly bears are resilient
BOZEMAN, Mont. — Grizzly bears in the Greater Yellowstone Ecosystem have been able to gain the body fat they need for hibernation even as population densities have increased and as climate change and human impacts have changed the availability of some foods, according to a new study by the U.S. Geological Survey and its partners.
- Overview
The Interagency Grizzly Bear Study Team (IGBST) is an interdisciplinary group of scientists and biologists responsible for long-term monitoring and research efforts on grizzly bears in the Greater Yellowstone Ecosystem (GYE). The team was formed by the Department of the Interior (DOI) in 1973 as a direct result of controversy surrounding the closure of open pit garbage dumps within Yellowstone National Park during 1968-72. IGBST members are representatives from the U.S. Geological Survey, National Park Service, U.S. Fish and Wildlife Service, U.S. Forest Service, the Eastern Shoshone and Northern Arapaho Tribal Fish and Game Department, and the States of Idaho, Montana, and Wyoming. This interagency approach ensures consistency in data collection and allows for combining limited resources to address information needs throughout the GYE.
The IGBST Leader serves as a technical and science advisor to the Interagency Grizzly Bear Committee and its Yellowstone Ecosystem Subcommittee, but is not a voting member of the committees.
The main objectives of the team are to 1) monitor the status and trend of the grizzly bear population in the GYE and 2) determine patterns of habitat use by bears and the relationship of land management activities to the welfare of the bear population. To meet these objectives, the team focuses on three main research areas.
Unique Females with Cubs-of-the-Year
Adult females are the most important demographic segment of the grizzly bear populations because they are the reproductive engine. Adult females with cubs-of-the-year (cubs) are the most easily and reliably recognized cohort of grizzly bear populations. Consequently females with cubs are a major focus of IGBST’s monitoring program in the Greater Yellowstone Ecosystem (GYE). Tracking trend for this segment of the population is generally representative of the trend for entire population. Thus, if we observe growth in numbers of female with cubs, we can be reasonably sure the entire population is growing. Efforts by IGBST to document the abundance and distribution of females with cubs began in 1973 and have improved over time by implementing standardized protocols and new statistical procedures. During the past 10 years (2006-2015), IGBST has estimated an average of 56 unique females with cubs annually. When combined with other data, these estimates serve as the basis for estimating total population size. Estimates of total population size are used by IGBST to evaluate annual mortality and to assess whether mortality is sustainable. Sustainable mortality establishes a limit on the number of grizzly deaths that can occur given population objectives. Information from these studies is crucial to evaluate trends in the grizzly bear population and assess the long-term health of the population.
Radio-Collaring Bears
IGBST began radiocollaring grizzly bears in the Greater Yellowstone Ecosystem (GYE) in 1975. Since then, we have radio-monitored over 830 individuals for varying durations, typically for 2 to 3 years. Over 100 individuals have been monitored during more than 5 different years. Our monitoring program changed in 1986 based on directions from the Interagency Grizzly Bear Committee’s Population Task Force. They recommended we maintain and monitor a minimum of 25 radio-collared adult females annually. We also use telemetry to monitor a representative sample of adult males. Data collected from radio-marked bears provide information necessary for tracking key population parameters. By observing radio-collared bears, we document age of first reproduction, average litter size, cub and yearling survival, how often a female produces a litter, and causes of mortality. These data allow us to estimate survival among different sex and age classes of bears. Collectively, this is referred to as “known-fate monitoring”. In conjunction with other estimates (i.e., number of females with cubs, annual mortality), this information is used estimate population size and evaluate sustainable mortality. Location information obtained from collared bears also provides reliable data that helps resource managers focus their activities toward landscape issues that impact grizzly bears in the GYE.
All research animals are handled by following the specific requirements of USGS Animal Care and Use policies.
Whitebark Pine Monitoring
Whitebark pine seeds are a high-calorie food resource available to grizzly bears during late summer and fall. Because whitebark pine is a masting species, cone production is variable, with good crops every 2 to 3 years. Whitebark pine seeds are high in fats and proteins and, when available, allow grizzly bears to build up fat reserves during fall in preparation for hibernation. Grizzly bears harvest these cones by raiding seed caches of red squirrels (middens). Since 1980, we have annually monitored whitebark pine cone production throughout the Greater Yellowstone Ecosystem (GYE) using surveys of established transects. Our data show that mature, cone-producing whitebark pine trees in the GYE have experienced substantial mortality, primarily due to a mountain pine beetle outbreak that started in the early 2000s, but also from white pine blister rust, and fire. IGBST research shows that grizzly bears are adapting to these changes by shifting their diets (see Food Synthesis Report). However, we will continue to monitor this food resource because bears still make extensive use of it in years of good cone production. Click here for IGBST Whitebark Pine Cone Production Annual Summaries.
FOR INFORMATION ABOUT GRIZZLY BEAR MORTALITY, SEE BOTTOM OF PAGE (below "Reports" section).
Direct Links:
Grizzly Bear Mortality Information (See "Grizzly Bear Mortality Information" near bottom of page)
Bear Caused Human Fatalities in the GYE, 1892 - Present
IGBST Grizzly Bear Food Synthesis Report
IGBST Whitebark Pine Cone Production Annual Summaries
Animated image showing grizzly bear range expansion in GYE: 1990-2020
Reports:
A Reassessment of Chao2 Estimates for Population Monitoring of Grizzly
IGBST Demographic Workshop Report
GRIZZLY BEAR MORTALITY INFORMATION:
Identifying the locations and causes of grizzly bear mortality is a key component in understanding the dynamics of this population. About 85% of all documented bear mortalities are human-caused. Tracking human-caused bear deaths helps define patterns and trends that can direct management programs designed to reduce bear mortality.
1) Documented known and probable grizzly bear mortalities in the Greater Yellowstone Ecosystem for 2022 can be found in a provisional USGS data release that is updated as grizzly bear mortalities are reported by IGBST member agencies throughout the year. Go to “Attached Files” and download the “GB_Mortality_2022 csv” file, which contains a table with all reported mortalities for the current year.
Important notice: Because the current year’s grizzly bear mortality data are continuously updated and thus subject to revision, they are considered preliminary data by the USGS. Therefore, if these data are used for any purpose, please refer to them as preliminary data (see full data disclaimer under the “Summary” section of the provisional data release). At the end of the calendar year, these data will be compiled, undergo additional review, and added to the existing data release listed below, which contains documented mortality data compiled by the IGBST since 2015. Once the current year’s data are added to the existing data release, they are no longer considered provisional, which will be reflected on this website.
2) Documented known and probable grizzly bear mortalities in the Greater Yellowstone Ecosystem during 2015-2021 can be found in a USGS data release.
3) 2009-2014 grizzly bear mortality tables can be found in IGBST Annual Reports of the same years.
- Science
Below are other science projects associated with this project.
IGBST Annual Reports
See below for IGBST Annual Reports from 1989 - 2020, which are available as PDFs; the latest version of Adobe Reader or similar software is required. Click on links below to access reports. Annual reports starting in 2021 can be found at the Interagency Grizzly Bear Committee (IGBC) website (click green button below). The IGBC also has the full set of IGBST reports.IGBST Grizzly Bear Food Synthesis Report
How to Cite: Interagency Grizzly Bear Study Team. 2013. Response of Yellowstone grizzly bears to changes in food resources: a synthesis. Report to the Interagency Grizzly Bear Committee and Yellowstone Ecosystem Subcommittee. Interagency Grizzly Bear Study Team, U.S. Geological Survey, Northern Rocky Mountain Science Center, Bozeman, Montana, USA.IGBST Whitebark Pine Cone Production Annual Summaries
Whitebark Pine reports from 2009-2020 are available in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view. Click on the links below to access the reports.History of the IGBST
A heated debate began in the 1960s and 1970s and grew to a national scope concerning the grizzly bears in the GYE. For decades, grizzly bears were allowed to rummage through garbage dumps searching for food. As early as the 1940s, some researchers suggested closing the open-pit dumps within Yellowstone National Park. In 1963, the Advisory Board on Wildlife Management in the National Parks released... - Multimedia
The IGBST has been capturing and radiocollaring grizzly bears since 1975. Data collected from marked bears provide the information necessary for tracking key population parameters. This gallery shows the process by which we capture and collar grizzly bears for research purposes. All research animals are handled by following the specific requirements of USGS Animal Care and Use policies.
Animated image showing grizzly bear range expansion in GYE: 1990-2020
Sequential estimates of occupied ranges for grizzly bears in the Greater Yellowstone Ecosystem during 1990–2020. Range extents are based on methods described in Bjornlie et al. (2014).
- Publications
IGBST Complete Publications 1974 - 2020
Filter Total Items: 84Physiological consequences of consuming low-energy foods: Herbivory coincides with a stress response in Yellowstone bears.
Meat, fruit, seeds and other high-energy bear foods are often highly localized and briefly available and understanding which factors influence bear consumption of these foods is a common focus of bear conservation and ecology. However, the most common bear foods, graminoids and forbs, are more widespread but of lower quality. We poorly understand how herbage consumption impacts bear physiology, suAuthorsDavid A Christianson, Tyler H Coleman, Quint Doan, Mark A. HaroldsonQuantifying energetic costs and defining energy landscapes experienced by grizzly bears
Animal movements are major determinants of energy expenditure and ultimately the cost–benefit of landscape use. Thus, we sought to understand those costs and how grizzly bears (Ursus arctos) move in mountainous landscapes. We trained captive grizzly bears to walk on a horizontal treadmill and up and down 10% and 20% slopes. The cost of moving upslope increased linearly with speed and slope angle,AuthorsAnthony M. Carnahan, Frank T. van Manen, Mark A. Haroldson, Gordon Stenhouse, Charles T. RobbinsMammal species composition and habitat associations in a commercial forest and mixed-plantation landscape
Commercial forest plantations of fast-growing species have been established globally to meet increasing demands for timber, pulpwood, and other wood products. Industrial plantations may contribute to tropical forest conservation by reducing exploitation of primary and secondary natural forests. Whether such plantations can support critical elements of biodiversity, including provision of habitat aAuthorsWai Pak Ng, Frank T. van Manen, Stuart P. Sharp, Siew Te Wong, Shyamala RatnayekeThermal constraints on energy balance, behaviour and spatial distribution of grizzly bears
1. Heat dissipation limit theory posits that energy available for growth and reproduction in endotherms is limited by their ability to dissipate heat. In mammals, endogenous heat production increases markedly during gestation and lactation, and thus female mammals may be subject to greater thermal constraints on energy expenditure than males. Such constraints likely have important implications forAuthorsSavannah A. Rogers, Charlie T. Robbins, Paul D. Mathewson, Anthony M. Carnahan, Frank T. van Manen, Mark A. Haroldson, Warren P. Porter, Taylor R. Rogers, Terrence Soule, Ryan A. LongAn evaluation of noninvasive sampling techniques for Malayan sun bears
Traditional mark–recapture studies to estimate abundance and trends of Malayan sun bear (Helarctos malayanus) populations are impeded by logistics of live-trapping wild individuals. The development of noninvasive sampling techniques for monitoring sun bear populations is therefore crucial for targeted conservation action. Sun bears have short fur, and conventional hair-snagging devices are ineffecAuthorsThye Lim Tee, Wai Ling Lai, Terence Kok Ju Wei, Ooi Zhuan Shern, Frank T. van Manen, Stuart P. Sharp, Siew Te Wong, Jactty Chew, Shyamala RatnayekeBrown Bear (Ursus arctos; North America)
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.AuthorsMark A. Haroldson, Melanie Clapham, Cecily M. Costello, Kerry A. Gunther, Kate Kendall, Sterling Miller, Karine Pigeon, Michael F. Proctor, Karyn D. Rode, Christopher Servheen, Gordon Stenhouse, Frank T. van ManenEcological and social dimensions of sloth bear conservation in Sri Lanka
Balancing the needs of humans and wildlife in Sri Lanka presents enormous socioeconomic and conservation challenges. Sloth bears are legally protected, but attacks on humans generate intense fear, which increases the potential for human-caused bear mortality and local extirpation of bears. In this chapter, what is known about the ecology and human dimensions of the sloth bear in a country with a tAuthorsShyamala Ratnayeke, Frank T. van ManenWhitebark pine cone production - 2020
No abstract available.AuthorsMark A. Haroldson, Frank T. van ManenPotential for recreational restrictions to reduce grizzly bear–caused human injuries
In 2011, 2 hikers were killed by grizzly bears (Ursus arctos) in separate incidents on backcountry trails in Hayden Valley, Yellowstone National Park, USA (YNP). Hayden Valley provides prime habitat for grizzly bears and is known to have high densities of bears. During 1970–2017, 23% (10 of 44) of all backcountry grizzly bear–inflicted human injuries and fatalities in YNP occurred in the valley evAuthorsKerry A. Gunther, Mark A. HaroldsonPrimarily resident grizzly bears respond to late-season elk harvest
Autumn ungulate hunting in the Greater Yellowstone Ecosystem carries the risk of hunter–grizzly bear (Ursus arctos) conflict and creates a substantial challenge for managers. For Grand Teton National Park, Wyoming, USA, a key information need is whether increased availability of elk (Cervus canadensis) carcasses during a late autumn (Nov–Dec) harvest within the national park attracts grizzly bearsAuthorsFrank T. van Manen, Michael R. Ebinger, David D. Gustine, Mark A. Haroldson, Katharine R. Wilmot, Craig WhitmanYellowstone grizzly bear investigations: Annual report of the Interagency Grizzly Bear Study Team 2018
This annual report summarizes the results of grizzly bear (Ursus arctos) research and monitoring conducted in the Greater Yellowstone Ecosystem (GYE) by the Interagency Grizzly Bear Study Team (IGBST) during 2018. The research and monitoring program is focused on population estimation and demographics, food monitoring, and habitat monitoring. The report also contains a summary of grizzly bear manaAuthorsFrank T. van Manen, Mark A. Haroldson, Bryn Karabensh - Web Tools
Current grizzly bear mortality tables are located on the Interagency Grizzly Bear Study Team main page (Overview tab) under the "Grizzly Bear Mortality Information" section
IGBST Interactive Map
This map shows the overlapping boundaries of significant ecological and land management areas in the Greater Yellowstone Ecosystem used by the IGBST to show grizzly bear distribution and occupancy. Click on each boundary for more information.
IGBST GIS Data Download
This links to the IGBST mapping boundary layers related to the teams research and monitoring that is available at this time. Resources include KMZ files, Metadata files, and Shape files.
IGBC Food Storage Regulation Map
Food Storage Regulations in Grizzly Bear Recovery Areas: If you are going to any of the Grizzly Bear Recovery Areas to camp, hunt or hike you may be required to keep your food, garbage and livestock feed in special bear-resistant containers. Once you have chosen your destination, you can find and read these “Food Storage Regulations” by clicking on the links listed on this page developed by IGBC.
- News
Below are news stories associated with this project.
In a changing ecosystem, Yellowstone grizzly bears are resilient
BOZEMAN, Mont. — Grizzly bears in the Greater Yellowstone Ecosystem have been able to gain the body fat they need for hibernation even as population densities have increased and as climate change and human impacts have changed the availability of some foods, according to a new study by the U.S. Geological Survey and its partners.
- Partners