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
Grizzly bear depredation on grazing allotments in the Yellowstone ecosystem
Estimating distemper virus dynamics among wolves and grizzly bears using serology and Bayesian state‐space models
Carnivore hotspots in Peninsular Malaysia and their landscape attributes
Size‐assortative choice and mate availability influences hybridization between red wolves (Canis rufus) and coyotes (Canis latrans)
Potential paths for male-mediated gene flow to and from an isolated grizzly bear population
Diet and macronutrient optimization in wild ursids: A comparison of grizzly bears with sympatric and allopatric black bears
Detecting grizzly bear use of ungulate carcasses using global positioning system telemetry and activity data
Multiple estimates of effective population size for monitoring a long-lived vertebrate: An application to Yellowstone grizzly bears
Whitebark pine, population density, and home-range size of grizzly bears in the greater Yellowstone ecosystem
Use of isotopic sulfur to determine whitebark pine consumption by Yellowstone bears: a reassessment
The economics of roadside bear viewing
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: 84Grizzly bear depredation on grazing allotments in the Yellowstone ecosystem
Grizzly bear (Ursus arctos) conflicts with humans, including livestock depredation on public land grazing allotments, have increased during the last several decades within the Greater Yellowstone Ecosystem (GYE) in the western United States as the grizzly bear population has grown in number and occupied range. Minimizing conflicts and improving conservation efficacy requires information on the relAuthorsSmith L. Wells, Lance B. McNew, Daniel B. Tyers, Frank T. van Manen, Daniel J. ThompsonEstimating distemper virus dynamics among wolves and grizzly bears using serology and Bayesian state‐space models
Many parasites infect multiple hosts, but estimating the transmission across host species remains a key challenge in disease ecology. We investigated the within and across host species dynamics of canine distemper virus (CDV) in grizzly bears (Ursus arctos) and wolves (Canis lupus) of the Greater Yellowstone Ecosystem (GYE). We hypothesized that grizzly bears may be more likely to be exposed to CDAuthorsPaul C. Cross, Frank T. van Manen, Mafalda Viana, Emily S. Almberg, Daniel Bachen, Ellen E. Brandell, Mark A. Haroldson, Peter J. Hudson, Daniel R. Stahler, Douglas W. SmithCarnivore hotspots in Peninsular Malaysia and their landscape attributes
Mammalian carnivores play a vital role in ecosystem functioning. However, they are prone to extinction because of low population densities and growth rates, and high levels of persecution or exploitation. In tropical biodiversity hotspots such as Peninsular Malaysia, rapid conversion of natural habitats threatens the persistence of this vulnerable group of animals. Here, we carried out the first cAuthorsShyamala Ratnayeke, Frank T. van Manen, Gopalasamy Reuben Clements, Noor Azleen Mohd Kulaimi, Stuart P. SharpSize‐assortative choice and mate availability influences hybridization between red wolves (Canis rufus) and coyotes (Canis latrans)
Anthropogenic hybridization of historically isolated taxa has become a primary conservation challenge for many imperiled species. Indeed, hybridization between red wolves (Canis rufus) and coyotes (Canis latrans) poses a significant challenge to red wolf recovery. We considered seven hypotheses to assess factors influencing hybridization between red wolves and coyotes via pair‐bonding between theAuthorsJoseph W. Hinton, John L. Gittleman, Frank T. van Manen, Michael J. ChamberlainPotential paths for male-mediated gene flow to and from an isolated grizzly bear population
For several decades, grizzly bear populations in the Greater Yellowstone Ecosystem (GYE) and the Northern Continental Divide Ecosystem (NCDE) have increased in numbers and range extent. The GYE population remains isolated and although effective population size has increased since the early 1980s, genetic connectivity between these populations remains a long-term management goal. With only ~110 kmAuthorsChristopher P. Peck, Frank T. van Manen, Cecily M. Costello, Mark A. Haroldson, Lisa Landenburger, Lori L. Roberts, Daniel D. Bjornlie, Richard D. MaceDiet and macronutrient optimization in wild ursids: A comparison of grizzly bears with sympatric and allopatric black bears
When fed ad libitum, ursids can maximize mass gain by selecting mixed diets wherein protein provides 17 ± 4% of digestible energy, relative to carbohydrates or lipids. In the wild, this ability is likely constrained by seasonal food availability, limits of intake rate as body size increases, and competition. By visiting locations of 37 individuals during 274 bear-days, we documented foods consumedAuthorsCecily M. Costello, Steven L. Cain, Shannon R Pils, Leslie Frattaroli, Mark A. Haroldson, Frank T. van ManenDetecting grizzly bear use of ungulate carcasses using global positioning system telemetry and activity data
Global positioning system (GPS) wildlife collars have revolutionized wildlife research. Studies of predation by free-ranging carnivores have particularly benefited from the application of location clustering algorithms to determine when and where predation events occur. These studies have changed our understanding of large carnivore behavior, but the gains have concentrated on obligate carnivores.AuthorsMichael R. Ebinger, Mark A. Haroldson, Frank T. van Manen, Cecily M. Costello, Daniel D. Bjornlie, Daniel J. Thompson, Kerry A. Gunther, Jennifer K. Fortin, Justin E. Teisberg, Shannon R Pils, P J White, Steven L. Cain, Paul C. CrossMultiple estimates of effective population size for monitoring a long-lived vertebrate: An application to Yellowstone grizzly bears
Effective population size (Ne) is a key parameter for monitoring the genetic health of threatened populations because it reflects a population's evolutionary potential and risk of extinction due to genetic stochasticity. However, its application to wildlife monitoring has been limited because it is difficult to measure in natural populations. The isolated and well-studied population of grizzly beaAuthorsPauline L. Kamath, Mark A. Haroldson, Gordon Luikart, David Paetkau, Craig L. Whitman, Frank T. van ManenWhitebark pine, population density, and home-range size of grizzly bears in the greater Yellowstone ecosystem
Changes in life history traits of species can be an important indicator of potential factors influencing populations. For grizzly bears (Ursus arctos) in the Greater Yellowstone Ecosystem (GYE), recent decline of whitebark pine (WBP; Pinus albicaulis), an important fall food resource, has been paired with a slowing of population growth following two decades of robust population increase. These obsAuthorsDaniel D. Bjornlie, Frank T. van Manen, Michael R. Ebinger, Mark A. Haroldson, Daniel J. Thompson, Cecily M. CostelloUse of isotopic sulfur to determine whitebark pine consumption by Yellowstone bears: a reassessment
Use of naturally occurring stable isotopes to estimate assimilated diet of bears is one of the single greatest breakthroughs in nutritional ecology during the past 20 years. Previous research in the Greater Yellowstone Ecosystem (GYE), USA, established a positive relationship between the stable isotope of sulfur (δ34S) and consumption of whitebark pine (Pinus albicaulis) seeds. That work combinedAuthorsCharles C. Schwartz, Justin E. Teisberg, Jennifer K. Fortin, Mark A. Haroldson, Christopher Servheen, Charles T. Robbins, Frank T. van ManenThe economics of roadside bear viewing
Viewing bears along roadside habitats is a popular recreational activity in certain national parks throughout the United States. However, safely managing visitors during traffic jams that result from this activity often requires the use of limited park resources. Using unique visitor survey data, this study quantifies economic values associated with roadside bear viewing in Yellowstone National PaAuthorsLeslie Richardson, Tatjana Rosen, Kerry Gunther, Chuck Schwartz - 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.