Interagency Grizzly Bear Study Team Active
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.
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
Reproductive maturation and senescence in the female brown bear
Use of sulfur and nitrogen stable isotopes to determine the importance of whitebark pine nuts to Yellowstone grizzly bears
Large carnivores, moose, and humans: A changing paradigm of predator management in the 21st century
Yellowstone grizzly bear investigations: Annual report of the Interagency Grizzly Bear Study Team, 2001
Estimating total human-caused mortality from reported mortality using data from radio-instrumented grizzly bears
Grizzly bear denning chronology and movements in the Greater Yellowstone Ecosystem
Consumption of fungal sporocarps by Yellowstone grizzly bears
Grizzly bear denning and potential conflict areas in the Greater Yellowstone Ecosystem
Distribution of grizzly bears in the Greater Yellowstone Ecosystem, 1990-2000
Negative binomial models for abundance estimation of multiple closed populations
On-line sulfur isotope analysis of organic material by direct combustion: Preliminary results and potential applications
Effects of exotic species on Yellowstone's grizzly bears
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
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.
Below are partners associated with this project.
- 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.
Sources/Usage: Some content may have restrictions. View Media DetailsUnique 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.
- 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: 84Reproductive maturation and senescence in the female brown bear
Changes in age-specific reproductive rates can have important implications for managing populations, but the number of female brown (grizzly) bears (Ursus arctos) observed in any one study is usually inadequate to quantify such patterns, especially for older females and in hunted areas. We examined patterns of reproductive maturation and senescence in female brown bears by combining data from 20 sAuthorsCharles C. Schwartz, Kim A. Keating, Harry V. Reynolds III, Victor G. Barnes, Richard A. Sellers, J. E. Swenson, Sterling D. Miller, B. N. McLellan, Jeffrey A. Keay, Robert McCann, Michael Gibeau, Wayne F. Wakkinen, Richard D. Mace, Wayne Kasworm, Rodger Smith, Steven HerreroUse of sulfur and nitrogen stable isotopes to determine the importance of whitebark pine nuts to Yellowstone grizzly bears
Whitebark pine (Pinus albicaulis) is a masting species that produces relatively large, fat- and protein-rich nuts that are consumed by grizzly bears (Ursus arctos horribilis). Trees produce abundant nut crops in some years and poor crops in other years. Grizzly bear survival in the Greater Yellowstone Ecosystem is strongly linked to variation in pine-nut availability. Because whitebark pine treesAuthorsL.A. Felicetti, C.C. Schwartz, R. O. Rye, M.A. Haroldson, K.A. Gunther, D.L. Phillips, C.T. RobbinsLarge carnivores, moose, and humans: A changing paradigm of predator management in the 21st century
We compare and contrast the evolution of human attitudes toward large carnivores between Europe and North America. In general, persecution of large carnivores began much earlier in Europe than North America. Likewise, conservation programs directed at restoration and recovery appeared in European history well before they did in North America. Together, the pattern suggests there has been an evolutAuthorsCharles C. Schwartz, J. E. Swenson, Sterling D. MillerYellowstone grizzly bear investigations: Annual report of the Interagency Grizzly Bear Study Team, 2001
The contents of this Annual Report summarize results of monitoring and research from the 2001 field season. The report also contains a summary of nuisance grizzly bear (Ursus arctos horribilis) management actions. In addition to our normal monitoring, we completed an array of studies addressing the potential impacts of winter recreation on denning grizzly bears. This research was in response to aEstimating total human-caused mortality from reported mortality using data from radio-instrumented grizzly bears
Tracking mortality of the Yellowstone grizzly bear (Ursus arctos horribilis) is an essential issue of the recovery process. Problem bears removed by agencies are well documented. Deaths of radiocollared bears are known or, in many cases, can be reliably inferred. Additionally, the public reports an unknown proportion of deaths of uncollared bears. Estimating the number of non-agency human-causedAuthorsS. Cherry, M.A. Haroldson, J. Robison-Cox, C.C. SchwartzGrizzly bear denning chronology and movements in the Greater Yellowstone Ecosystem
Den entrance and emergence dates of grizzly bears (Ursus arctos) in the Greater Yellowstone Ecosystem are important to management agencies that wish to minimize impacts of human activities on bears. Current estimates for grizzly bear denning events use data that were collected from 1975–80. We update these estimates by including data obtained from 1981–99. We used aerial telemetry data to estimateAuthorsMark A. Haroldson, Mark A. Ternent, Kerry A. Gunther, Charles C. SchwartzConsumption of fungal sporocarps by Yellowstone grizzly bears
Sign of grizzly bears (Ursus arctos horribilis) consuming fungal sporocarps (mushrooms and truffles) was observed on 68 occasions during a study of radiomarked bears in the Yellowstone region, 1977–96. Sporocarps also were detected in 96 grizzly bear feces. Most fungi consumedby Yellowstone's grizzlybearsweremembersofthe Boletaceae(Suillus spp.), Russulaceae (Russula spp. and Lactarius sp.), MorcAuthorsDavid J. Mattson, Shannon Podruzny, Mark A. HaroldsonGrizzly bear denning and potential conflict areas in the Greater Yellowstone Ecosystem
Increasing winter use of steep, high-elevation terrain by backcountry recreationists has elevated concern about disturbance of denning grizzly bears (Ursus arctos) in the Greater Yellowstone Ecosystem (GYE). To help identify areas where such conflicts might occur, we developed a spatially explicit model to predict potential denning areas in the GYE. Using a scan area of 630 m around each location,AuthorsShannon Podruzny, Steve Cherry, Charles C. Schwartz, Lisa LandenburgerDistribution of grizzly bears in the Greater Yellowstone Ecosystem, 1990-2000
The Yellowstone grizzly bear (Ursus arctos horribilis) has been expanding its range during the past 2 decades and now occupies historic habitats that had been vacant. A current understanding of the distribution of grizzly bears within the ecosystem is useful in the recovery process and to help guide the state and federal land management agencies and state wildlife agencies of Idaho, Wyoming, and MAuthorsCharles C. Schwartz, Mark A. Haroldson, Kerry A. Gunther, D. MoodyNegative binomial models for abundance estimation of multiple closed populations
Counts of uniquely identified individuals in a population offer opportunities to estimate abundance. However, for various reasons such counts may be burdened by heterogeneity in the probability of being detected. Theoretical arguments and empirical evidence demonstrate that the negative binomial distribution (NBD) is a useful characterization for counts from biological populations with heterogeneiAuthorsMark S. Boyce, Darry I. MacKenzie, Bryan F.J. Manly, Mark A. Haroldson, David W. MoodyOn-line sulfur isotope analysis of organic material by direct combustion: Preliminary results and potential applications
Sulfur isotopes have received little attention in ecology studies because plant and animal materials typically have low sulfur concentrations (< 1 wt.%) necessitating labor-intensive chemical extraction prior to analysis. To address the potential of direct combustion of organic material in an elemental analyzer coupled with a mass spectrometer, we compared results obtained by direct combustion toAuthorsC.L. Kester, R. O. Rye, C.A. Johnson, C.H. Schwartz, C.H. HolmesEffects of exotic species on Yellowstone's grizzly bears
Humans have affected grizzly bears (Ursus arctos horribilis) by direct mortality, competition for space and resources, and introduction of exotic species. Exotic organisms that have affected grizzly bears in the Greater Yellowstone Area include common dandelion (Taraxacum officinale), nonnative clovers (Trifolium spp.), domesticated livestock, bovine brucellosis (Brucella abortus), lake trout (SalAuthorsDaniel P. Reinhart, Mark A. Haroldson, D.J. Mattson, Kerry A. Gunther - 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
- 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
Below are partners associated with this project.