Mark Haroldson
Mark Haroldson is an emeritus USGS Wildlife Biologist for the Interagency Grizzly Bears Study Team and works out of the Northern Rocky Mountain Science Center, Bozeman, MT.
Research Interest
Mark has had a passion for bears since he began studying them as an undergraduate in 1976. He has worked in bear research and management in several western states ever since. Since 1984 he has worked in various capacities for the Interagency Grizzly Bear Study Team in the Greater Yellowstone Ecosystem. Current research is focused on mortality and population trend of grizzly bears in the Greater Yellowstone Ecosystem.
Education and Certifications
B.S. Wildlife Biology, 1979, University of Montana
Graduate level class work, 1982-88, University of Montana
Science and Products
Informing Management Options for Grizzly Bears in a Changing Greater Yellowstone Ecosystem
Project Overview The iconic grizzly bear of the Greater Yellowstone Ecosystem has exhibited a remarkable recovery in response to concerted conservation actions implemented since its listing as threatened under the Endangered Species Act in 1975. However, information regarding the potential effects and timing of climate change in conjunction with increasing human recreation and...
Interagency Grizzly Bear Study Team
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...
NOROCK Large Carnivore Research Program
NOROCK has substantial expertise in large carnivore research, primarily involving species listed as Threatened or Endangered. NOROCK’s Large Carnivore Research Program includes scientists from NOROCK’s Headquarters, West Glacier Field Station, and the Southern Appalachian Field Station. Studies are conducted in a wide variety of landscapes throughout the U.S., as well as international research...
Mortality, morphology, and water chemistry for 6PPD-quinone exposed coho embryos Mortality, morphology, and water chemistry for 6PPD-quinone exposed coho embryos
Understanding evolutionary processes that drive population dynamics is critical in ecology. Measuring the performance-density relationship in long-lived mammalian species demands long-term data, limiting the ability to observe such mechanisms. We tested density-dependent (intrinsic) and density-independent (extrinsic) drivers of body composition of grizzly bears (Ursus arctos) in the...
Body composition data of grizzly bears in the Greater Yellowstone Ecosystem 2000-2020 Body composition data of grizzly bears in the Greater Yellowstone Ecosystem 2000-2020
Understanding evolutionary processes that drive population dynamics is critical in ecology. Measuring the performance-density relationship in long-lived mammalian species demands long-term data, limiting the ability to observe such mechanisms. We tested density-dependent (intrinsic) and density-independent (extrinsic) drivers of body composition of grizzly bears (Ursus arctos) in the...
Documented known and probable grizzly bear mortalities in the Greater Yellowstone Ecosystem, 2015-2024 (ver. 4.0 May 2025) Documented known and probable grizzly bear mortalities in the Greater Yellowstone Ecosystem, 2015-2024 (ver. 4.0 May 2025)
The Interagency Grizzly Bear Study Team (IGBST) evaluates mortalities for population segments within the DMA by deriving estimates of total mortality for independent-age (2 years or older) females and independent-age males, including estimates of unknown/unreported mortalities based on Cherry et al. (2002). We then determine the total annual mortality rate for these segments as a percent...
Detection histories of grizzly bears in Grand Teton National Park, 2014-2015 Detection histories of grizzly bears in Grand Teton National Park, 2014-2015
This dataset contains detection histories of grizzly bears in areas of Grand Teton National Park that are open for elk harvest as part of the Elk Reduction Program. Sampling followed a robust design analysis with 6 primary sampling periods of 4 weekly secondary sampling periods each during 2014-2015. In both years, primary sampling periods were in July-August (no elk hunt), September...
Canine distemper virus antibody titer results for grizzly bears and wolves in the Greater Yellowstone Ecosystem 1984-2014 Canine distemper virus antibody titer results for grizzly bears and wolves in the Greater Yellowstone Ecosystem 1984-2014
We investigated the dynamics of canine distemper virus (CDV) in grizzly bears (Ursus arctos) and wolves (Canis lupus) of the Greater Yellowstone Ecosystem using serological data collected from 1984 to 2014. 565 sera samples were obtained from 425 unique grizzly bears (134 females and 291 males) from 1984 to 2014 and 319 sera samples were obtained from 285 unique wolves (130 females and...
Potential movement paths for male grizzly bear (Ursus arctos) dispersal between the Northern Continental Divide and Greater Yellowstone Ecosystems, 2000-2015 Potential movement paths for male grizzly bear (Ursus arctos) dispersal between the Northern Continental Divide and Greater Yellowstone Ecosystems, 2000-2015
For several decades, grizzly bear (Ursus arctos) populations in the Greater Yellowstone Ecosystem (GYE) and the Northern Continental Divide Ecosystem (NCDE) have increased in numbers and range extent. Whereas the NCDE population is contiguous with grizzly bear populations in the Canadian Rocky Mountains, genetic evidence suggests the GYE population remains isolated. Recent analyses...
Filter Total Items: 91
An energetic tradeoff best explains parturition timing in grizzly bears An energetic tradeoff best explains parturition timing in grizzly bears
Timing of grizzly bear (Ursus arctos) parturition during hibernation has been explained by ancestral traits (delayed implantation, altricial young, obligate maternal denning), but the ultimate driver underlying precise timing has not been fully explored. Capitalizing on an observed latitudinal increase in denning duration among four populations in interior North America, we tested two...
Authors
C. M. Costello, L. L. Roberts, D. D. Bjornlie, M. D. Cameron, J. G. Clapp, Mark Haroldson, G. V. Hilderbrand, K. Joly, W. Kasworm, J. M. Nicholson, T. Radandt, M. S. Sorum, J. E. Teisberg, Frank T. van Manen, M. A. Vinks
A summary of grizzly bear distribution in the lower-48 US states in 2024 A summary of grizzly bear distribution in the lower-48 US states in 2024
Understanding the distribution of grizzly bear populations in the lower-48 states, is important for their conservation and management, and for public safety. Previously, our research teams working in grizzly bear ecosystems in the lower-48 states used varying methods to estimate distribution of grizzly bear populations. In the Greater Yellowstone Ecosystem (GYE) and Northern Continental...
Authors
Cecily M. Costello, Justin A. Dellinger, Jennifer K. Fortin-Noreus, Mark Haroldson, Bryn Karabensh, Wayne F. Kasworm, Lori L. Roberts, Justin E. Teisberg, Frank T. van Manen, Tyler J. Vent
Bioclimatic, demographic, and anthropogenic correlates of grizzly bear activity patterns in the Greater Yellowstone Ecosystem Bioclimatic, demographic, and anthropogenic correlates of grizzly bear activity patterns in the Greater Yellowstone Ecosystem
Plasticity of diel activity rhythms may be a key element for adaptations of wildlife populations to changing environmental conditions. In the last decades, grizzly bears Ursus arctos in the Greater Yellowstone Ecosystem (GYE) have experienced notable environmental fluctuations, including changes in availability of food sources and severe droughts. Although substantial research has been...
Authors
A. Donatelli, Mark Haroldson, Justin G. Clapp, P. Ciucci, Frank T. van Manen
Exploring the exploitation of migratory moths by radio-marked grizzly bears in Wyoming Exploring the exploitation of migratory moths by radio-marked grizzly bears in Wyoming
Grizzly bear (Ursus arctos) feeding on migratory army cutworm moths (Euxoa auxiliaris) was first documented by the Interagency Grizzly Bear Study Team (IGBST) during the early 1980s in the southeastern portion of the Greater Yellowstone Ecosystem (GYE). Since those initial observations, use of this seasonally available food resource by grizzly bears has grown substantially. As of 2023...
Authors
Justin Clapp, Mark Haroldson, Justin A. Dellinger, Daniel D. Bjornlie, Daniel J. Thomposon, Frank T. van Manen
The influence of human presence and footprint on animal space use in US national parks The influence of human presence and footprint on animal space use in US national parks
Given the importance of protected areas for biodiversity, the growth of visitation to many areas has raised concerns about the effects of humans on wildlife. In 2020, the COVID-19 pandemic led to temporary closure of national parks in the United States, offering a pseudonatural experiment to tease apart the effects of permanent infrastructure and transient human presence on animals. We...
Authors
Kaitlyn M. Gaynor, Forest Hayes, Kezia R. Manlove, Nathan L. Galloway, John F. Benson, Michael J. Cherry, Clinton W. Epps, Robert J. Fletcher, John L. Orrock, Justine A. Smith, Christina M. Aiello, Jerrold L. Belant, Joel Berger, Mark Biel, Jill Bright, Joseph K. Bump, Michael Burchett, Carson Butler, Jennifer Carlson, Eric K. Cole, Neal Darby, Erin DeGutis, Sarah Dewey, Pete Figura, Tom Gable, Jeff Gagnon, Danielle M. Glass, Jennifer R. Green, Kerry A. Gunther, Mark Haroldson, Kent Hersey, Brandon Holton, Austin T. Homkes, Sarah R. Hoy, Debra Hughson, Kyle Joly, Ryan Leahy, Caitlin Lee-Roney, Rob Lester, Daniel MacNulty, Michael Magnuson, Daniel J. Martin, Rachel Mazur, Seth A. Moore, Elizabeth K. Orning, Katie Patrick, Rolf O. Peterson, Lynette Potvin, Paige Prentice, Seth P.D. Riley, Mark C. Romanski, Annette Roug, Jeff A. Sikich, Nova Simpson, William B. Sloan, Douglas W. Smith, Mathew Sorum, Scott Sprague, Daniel Stahler, John A. Stephenson, Thomas R. Stephenson, Janice Stroud-Settles, Frank T. van Manen, John A. Vucetich, Kate Wilmot, Steve K. Windels, Tiffany Wolf, Paul C. Cross
Female and male grizzly bears differ in their responses to low-intensity recreation in a protected area Female and male grizzly bears differ in their responses to low-intensity recreation in a protected area
Strategies animals use to navigate human-dominated landscapes frequently mimic anti-predator responses employed by prey species. Understanding how large carnivores respond to outdoor recreation is important for conservation, particularly in protected areas with preservation mandates. Visitation to Yellowstone National Park doubled from 1980 to 2015, increasing the need to examine...
Authors
Elise Loggers, Andrea R. Litt, Mark Haroldson, Kerry A. Gunther, Frank T. van Manen
Science and Products
Informing Management Options for Grizzly Bears in a Changing Greater Yellowstone Ecosystem
Project Overview The iconic grizzly bear of the Greater Yellowstone Ecosystem has exhibited a remarkable recovery in response to concerted conservation actions implemented since its listing as threatened under the Endangered Species Act in 1975. However, information regarding the potential effects and timing of climate change in conjunction with increasing human recreation and...
Interagency Grizzly Bear Study Team
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...
NOROCK Large Carnivore Research Program
NOROCK has substantial expertise in large carnivore research, primarily involving species listed as Threatened or Endangered. NOROCK’s Large Carnivore Research Program includes scientists from NOROCK’s Headquarters, West Glacier Field Station, and the Southern Appalachian Field Station. Studies are conducted in a wide variety of landscapes throughout the U.S., as well as international research...
Mortality, morphology, and water chemistry for 6PPD-quinone exposed coho embryos Mortality, morphology, and water chemistry for 6PPD-quinone exposed coho embryos
Understanding evolutionary processes that drive population dynamics is critical in ecology. Measuring the performance-density relationship in long-lived mammalian species demands long-term data, limiting the ability to observe such mechanisms. We tested density-dependent (intrinsic) and density-independent (extrinsic) drivers of body composition of grizzly bears (Ursus arctos) in the...
Body composition data of grizzly bears in the Greater Yellowstone Ecosystem 2000-2020 Body composition data of grizzly bears in the Greater Yellowstone Ecosystem 2000-2020
Understanding evolutionary processes that drive population dynamics is critical in ecology. Measuring the performance-density relationship in long-lived mammalian species demands long-term data, limiting the ability to observe such mechanisms. We tested density-dependent (intrinsic) and density-independent (extrinsic) drivers of body composition of grizzly bears (Ursus arctos) in the...
Documented known and probable grizzly bear mortalities in the Greater Yellowstone Ecosystem, 2015-2024 (ver. 4.0 May 2025) Documented known and probable grizzly bear mortalities in the Greater Yellowstone Ecosystem, 2015-2024 (ver. 4.0 May 2025)
The Interagency Grizzly Bear Study Team (IGBST) evaluates mortalities for population segments within the DMA by deriving estimates of total mortality for independent-age (2 years or older) females and independent-age males, including estimates of unknown/unreported mortalities based on Cherry et al. (2002). We then determine the total annual mortality rate for these segments as a percent...
Detection histories of grizzly bears in Grand Teton National Park, 2014-2015 Detection histories of grizzly bears in Grand Teton National Park, 2014-2015
This dataset contains detection histories of grizzly bears in areas of Grand Teton National Park that are open for elk harvest as part of the Elk Reduction Program. Sampling followed a robust design analysis with 6 primary sampling periods of 4 weekly secondary sampling periods each during 2014-2015. In both years, primary sampling periods were in July-August (no elk hunt), September...
Canine distemper virus antibody titer results for grizzly bears and wolves in the Greater Yellowstone Ecosystem 1984-2014 Canine distemper virus antibody titer results for grizzly bears and wolves in the Greater Yellowstone Ecosystem 1984-2014
We investigated the dynamics of canine distemper virus (CDV) in grizzly bears (Ursus arctos) and wolves (Canis lupus) of the Greater Yellowstone Ecosystem using serological data collected from 1984 to 2014. 565 sera samples were obtained from 425 unique grizzly bears (134 females and 291 males) from 1984 to 2014 and 319 sera samples were obtained from 285 unique wolves (130 females and...
Potential movement paths for male grizzly bear (Ursus arctos) dispersal between the Northern Continental Divide and Greater Yellowstone Ecosystems, 2000-2015 Potential movement paths for male grizzly bear (Ursus arctos) dispersal between the Northern Continental Divide and Greater Yellowstone Ecosystems, 2000-2015
For several decades, grizzly bear (Ursus arctos) populations in the Greater Yellowstone Ecosystem (GYE) and the Northern Continental Divide Ecosystem (NCDE) have increased in numbers and range extent. Whereas the NCDE population is contiguous with grizzly bear populations in the Canadian Rocky Mountains, genetic evidence suggests the GYE population remains isolated. Recent analyses...
Filter Total Items: 91
An energetic tradeoff best explains parturition timing in grizzly bears An energetic tradeoff best explains parturition timing in grizzly bears
Timing of grizzly bear (Ursus arctos) parturition during hibernation has been explained by ancestral traits (delayed implantation, altricial young, obligate maternal denning), but the ultimate driver underlying precise timing has not been fully explored. Capitalizing on an observed latitudinal increase in denning duration among four populations in interior North America, we tested two...
Authors
C. M. Costello, L. L. Roberts, D. D. Bjornlie, M. D. Cameron, J. G. Clapp, Mark Haroldson, G. V. Hilderbrand, K. Joly, W. Kasworm, J. M. Nicholson, T. Radandt, M. S. Sorum, J. E. Teisberg, Frank T. van Manen, M. A. Vinks
A summary of grizzly bear distribution in the lower-48 US states in 2024 A summary of grizzly bear distribution in the lower-48 US states in 2024
Understanding the distribution of grizzly bear populations in the lower-48 states, is important for their conservation and management, and for public safety. Previously, our research teams working in grizzly bear ecosystems in the lower-48 states used varying methods to estimate distribution of grizzly bear populations. In the Greater Yellowstone Ecosystem (GYE) and Northern Continental...
Authors
Cecily M. Costello, Justin A. Dellinger, Jennifer K. Fortin-Noreus, Mark Haroldson, Bryn Karabensh, Wayne F. Kasworm, Lori L. Roberts, Justin E. Teisberg, Frank T. van Manen, Tyler J. Vent
Bioclimatic, demographic, and anthropogenic correlates of grizzly bear activity patterns in the Greater Yellowstone Ecosystem Bioclimatic, demographic, and anthropogenic correlates of grizzly bear activity patterns in the Greater Yellowstone Ecosystem
Plasticity of diel activity rhythms may be a key element for adaptations of wildlife populations to changing environmental conditions. In the last decades, grizzly bears Ursus arctos in the Greater Yellowstone Ecosystem (GYE) have experienced notable environmental fluctuations, including changes in availability of food sources and severe droughts. Although substantial research has been...
Authors
A. Donatelli, Mark Haroldson, Justin G. Clapp, P. Ciucci, Frank T. van Manen
Exploring the exploitation of migratory moths by radio-marked grizzly bears in Wyoming Exploring the exploitation of migratory moths by radio-marked grizzly bears in Wyoming
Grizzly bear (Ursus arctos) feeding on migratory army cutworm moths (Euxoa auxiliaris) was first documented by the Interagency Grizzly Bear Study Team (IGBST) during the early 1980s in the southeastern portion of the Greater Yellowstone Ecosystem (GYE). Since those initial observations, use of this seasonally available food resource by grizzly bears has grown substantially. As of 2023...
Authors
Justin Clapp, Mark Haroldson, Justin A. Dellinger, Daniel D. Bjornlie, Daniel J. Thomposon, Frank T. van Manen
The influence of human presence and footprint on animal space use in US national parks The influence of human presence and footprint on animal space use in US national parks
Given the importance of protected areas for biodiversity, the growth of visitation to many areas has raised concerns about the effects of humans on wildlife. In 2020, the COVID-19 pandemic led to temporary closure of national parks in the United States, offering a pseudonatural experiment to tease apart the effects of permanent infrastructure and transient human presence on animals. We...
Authors
Kaitlyn M. Gaynor, Forest Hayes, Kezia R. Manlove, Nathan L. Galloway, John F. Benson, Michael J. Cherry, Clinton W. Epps, Robert J. Fletcher, John L. Orrock, Justine A. Smith, Christina M. Aiello, Jerrold L. Belant, Joel Berger, Mark Biel, Jill Bright, Joseph K. Bump, Michael Burchett, Carson Butler, Jennifer Carlson, Eric K. Cole, Neal Darby, Erin DeGutis, Sarah Dewey, Pete Figura, Tom Gable, Jeff Gagnon, Danielle M. Glass, Jennifer R. Green, Kerry A. Gunther, Mark Haroldson, Kent Hersey, Brandon Holton, Austin T. Homkes, Sarah R. Hoy, Debra Hughson, Kyle Joly, Ryan Leahy, Caitlin Lee-Roney, Rob Lester, Daniel MacNulty, Michael Magnuson, Daniel J. Martin, Rachel Mazur, Seth A. Moore, Elizabeth K. Orning, Katie Patrick, Rolf O. Peterson, Lynette Potvin, Paige Prentice, Seth P.D. Riley, Mark C. Romanski, Annette Roug, Jeff A. Sikich, Nova Simpson, William B. Sloan, Douglas W. Smith, Mathew Sorum, Scott Sprague, Daniel Stahler, John A. Stephenson, Thomas R. Stephenson, Janice Stroud-Settles, Frank T. van Manen, John A. Vucetich, Kate Wilmot, Steve K. Windels, Tiffany Wolf, Paul C. Cross
Female and male grizzly bears differ in their responses to low-intensity recreation in a protected area Female and male grizzly bears differ in their responses to low-intensity recreation in a protected area
Strategies animals use to navigate human-dominated landscapes frequently mimic anti-predator responses employed by prey species. Understanding how large carnivores respond to outdoor recreation is important for conservation, particularly in protected areas with preservation mandates. Visitation to Yellowstone National Park doubled from 1980 to 2015, increasing the need to examine...
Authors
Elise Loggers, Andrea R. Litt, Mark Haroldson, Kerry A. Gunther, Frank T. van Manen