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Northern Divide Grizzly Bear Project 2002-2008



  • Estimate of Population Size: Use sign surveys and systematic hair snag stations to obtain an estimate of the number of grizzly bears in the Northern Continental Divide Ecosystem (NCDE) in northwest Montana.
  • Genetic Library: Develop a genetic database for grizzly bears in the NCDE to assess genetic diversity and degree of relatedness of the NCDE grizzly bear population.


North American range map for grizzly bears (Ursus arctos)Grizzly bears (Ursus arctos horribilis) once roamed most of the North American continent. Habitat destruction and direct conflicts with humans have reduced their range by 99% in the lower 48 states (right, click on map for larger version). In 1975 grizzly bears were listed as threatened under the Endangered Species Act. The Northern Continental Divide Ecosystem (NCDE) in northwest Montana is one of six recovery zones defined in the Grizzly Bear Recovery Plan (U.S. Fish and Wildlife Service 1993). The NCDE is the third largest in area, potentially harbors the greatest number of grizzly bears, and is the only zone contiguous to a strong Canadian population. For these reasons it may have the best prospect of long-term survival for this threatened species. Estimates place the total number of grizzlies that remain south of the Canadian border at fewer than 1100. No reliable estimate currently exists for the grizzly bear population in the NCDE. For more information about grizzly bear recovery, visit the U.S. F&WS Grizzly Bear Recovery Office webpage.

For years, an estimate of the grizzly bear population size in the NCDE was identified by land managers as their highest priority and considered a critical component in assessing grizzly bear recovery efforts in the NCDE. A scientific review panel was established in 2002 in order to determine the optimal methods for obtaining this estimate. The unanimous conclusion of the panel was that noninvasive genetic sampling was the most powerful and reliable method available. The U.S. Geological Survey (USGS) was selected to lead the project due to their impartiality and expertise in this field of research.

Initial funding was secured in fiscal year 2003 to begin planning and preliminary fieldwork. In order to complete field work in 2004, a great deal of work had to be accomplished before crews ever began sampling. It was necessary to develop agreements with partner agencies, obtain permission from private landowners to access their land, construct temporary fences to ensure the integrity of sampling stations, and develop survey routes. See Field Methods below to learn more about our sampling strategies.

The greater NCDE is 32,300 km2 (8 million acres) of extremely diverse habitats, much of it being heavily forested, mountainous, and a largely roadless wilderness. Previously, statistically rigorous population studies in forested areas could only be accomplished with radio telemetry where large numbers of bears are captured, collared, and tracked. This impacts individual bears and the presence of collared/marked bears and frequent overflights impinge on backcountry users' wilderness and solitude experiences. However, there are now sampling methods and genetic techniques available that provide less intrusive approaches for acquiring reliable population data.

Genetic techniques provide the ability to identify species, individuals, and gender from bear DNA which is obtained from hair. With an appropriate design, bear sign survey methodology (hair found on trees and posts that bears naturally rub on) and systematic hair snag stations (baited stations located away from trails and developed areas), can be used to estimate the population size of grizzly bears. The amount of genetic variation within the population can be described using information from both sampling designs.

Study Area

Northern Divide Grizzly Bear Project Study Area MapGrizzly bears are present throughout most of the Northern Continental Divide Ecosystem. The study area of the Northern Divide Grizzly Bear Project encompasses 31,409 km2 (7.6 million acres) and extends from the Canadian border to approximately Hwy 200 (right, click on map for larger version). It includes Glacier National Park (NP), parts of five national forests (Flathead, Helena, Kootenai, Lewis and Clark, and Lolo), parts of the Blackfeet and Flathead Indian Reservations, and significant amounts of state and private land. Within the national forest lands are five Wilderness areas (Bob Marshall, Mission Mountains, Rattlesnake, Great Bear, and Scapegoat) and one wilderness study area (Deep Creek North). Officially designated roadless areas comprise 34% of the study area. Ninety nine percent of Glacier NP is roadless and managed as wilderness. With the addition of the park, 50% of the study area is roadless. There are 6,900 km (4,300 mi) of trail in the NCDE. The study area is a region of diverse land use with a central core of rugged mountains managed as national park, wilderness, and multiple-use forest lands surrounded by lower elevation state and corporate timber lands, state game preserves, private ranch lands, and towns. Many agreements have been made between the USGS and the agencies that manage the lands included in the study area. Written permission was also obtained from hundreds of private landowners that have property inside the study area. A significant amount of the study area is private land, therefore it is very important in order for this project to be a success to not only get permission from these landowners to access their land, but also to involve them in the study. Private landowners have intimate knowledge of the presence of and travel routes of grizzly bears on their land.

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Field Methods

The 7.76 million acre study area is divided into 9 subunits for logistical reasons. Subunit leaders coordinate the work of the field crews in their area, including quality control personnel responsible for working with crews to ensure correct and consistent application of the study protocols. All field work is done on foot during this study, with 55 crew members in 2003 and 190 crew members in 2004. The 2003 field season ran from May 19 -August 20 (a longer field season was planned but forest fires cut the field season short). The 2004 field season ran from June 1 - September 1.


grizzly bear in a bear hair trap - remote camera photoTo sample bears systematically throughout the ecosystem, the study area is divided into 660 7x7 km cells. A barbed wire hair snag station is placed in each cell and baited with a non-rewarding liquid scent lure. In areas where cattle are present, temporary fences have to be constructed around each station to prevent cattle from reaching the site. Cattle tend to enter the hair snag stations and deposit their hair on the barbed wire, sometimes destroying the station in the process. During the 2003 field season crews built 423 cattle exclusion fences in preparation for the 2004 field season (map).

The 2003 forest fires burned approximately 5% of the 8 million acre study area. The study accommodated for the change in bear use of these areas during site selection of the 2004 hair snag stations. Snag sites were selected based on bear habitat quality and expert knowledge of bear activity patterns. Sites within heavily burned areas may be avoided if there is no longer good habitat and lightly burned areas can still offer quality sites.

bear hair on barbed wire bear hair trapDuring the 2004 field season crews set up hair snag stations in each of the 641 grid cells. Hair snag stations were relocated within each cell every two weeks for four sessions.Samples were collected from hair snag stations after they had been out for 14 days. Field crews were able to reach the large majority of the sites despite challenging off-trail conditions. Hair was collected from the 4-point barbs using tweezers, placed in paper collection envelopes, and stored in desiccation chambers at the end of each 14 day period.

Remote cameras have been placed at some hair snag sites to learn more about how bears behave at these sites (photos and video).


grizzly bear rubbing on a bear rub treeDuring the 2003 field season crews conducted surveys to locate bear rub objects throughout the study area. Rub object surveys involve hiking trails, forest roads, and other areas throughout the ecosystem and collecting hair from trees, cabins, posts, power poles, or other objects that bears rub on as they travel through an area. A total of 5,350 rub objects were located and marked in 2003 (map). The rub object locations were entered into a Geographic Information System (GIS) in order to assist field personnel locating the rub objects in 2004 during the hair collection efforts. Information such as tree species, diameter, and distance from trail were recorded and entered into a database.

Bear rubs were setup in a few different ways. Ideally the objects would be marked with small, reflective tags and short pieces of barbed wire would be attached to the rubbing surface. The short pieces of barbed wire are used to ensure quality samples are obtained. However, in cases where a bear rub object (such as a tree) was located on a trail used by stock, the barbed wire was only affixed to the tree if the rub surface was more than one meter from the center of the trail. The rub object was setup in this way so that horses traveling down the trail won't be hurt or their packs damaged. If the tree was closer than a meter to a trail used by pack stock it was highly likely the tree was also a pack bump tree (tree that is bumped by stock or packs attached to stock as they walk down the trail). During the fall of 2003, we looked into alternatives to barbed wire for these trees that would not harm horses or their packs, and the best result came from barbless wire attached in a vertical position on the tree. During the first session of 2004 field sampling barbless wire was attached vertically to these pack bump trees. If the rub object was a fence, the fence wire next to the rub area was marked with paint to mark it.

bear hair snaged on barbed wire on a bear rub tree The 2003 forest fires burned approximately 5% of our 7.6 million acre study area. Approximately 315 (6%) of the study's rub objects were within the 2003 fire perimeters. The study accommodated for the change in bear use of these areas by working with the rub objects not impacted by fire and by identifying new rub objects. Also, as observed during the Greater Glacier Study, bears continue to use the burned rub objects that are still standing.

During the 2004 field season crews have been hiking trails and forest roads several times looking for any bear hair deposited on the rub objects since the previous survey. Hair found on each barb is considered a distinct sample. Using tweezers, samples are placed in paper collection envelopes and stored in desiccation chambers.

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Genetic Methods


Geneticists can determine the species, gender, and unique identity of a bear using the DNA contained within their hair. Prior to DNA extraction, each hair sample is examined to identify and isolate intact follicles. Acceptable DNA extraction rates are achieved with hair samples with at least five follicles and are the standard for this project. The hair follicles (5-10) are inserted into a solution that will breakdown the protein coat that surrounds the DNA in the follicle. The samples are then repeatedly "washed" chemically to remove any cellular debris and then stored in a refrigerator until DNA analysis is conducted.


Specific regions (called microsatellites) in the nuclear DNA (n DNA) are amplified using an optimized polymerase chain reaction (PCR) method and analyzed. This process yields information from one locus to determine the species, six additional loci to determine unique identity, and a separate gender-specific locus to determine sex. This project intends to use 15 loci to determine the level of genetic variation of the NCDE population.

While genetic techniques are a relatively new tool for biologists, there have been many projects undertaken that have advanced the methods of sampling and analysis.

Data Analysis Methods

The number of grizzly bears in the population will be estimated with mark-recapture models using DNA "fingerprints" of bears identified from hair snagging in conjunction with those identified from rub object surveys.


Field Results: Field activities went well during the summer of 2004. Lower than expected spring runoff allowed crews to cross creeks and reach backcountry sites early. Rain in June, early July, and late August has kept fire danger at moderate levels in most of the study area. Crews collected approximately 34,000 hair samples (with approximately 21,000 collected from hair snag stations and 13,000 from bear rubs).

Genetic Analysis: Hair samples collected during the 2004 field season identified a total of 545 individual grizzly bears.

Data/Statistical Analysis: Data analysis and population modeling have been completed. The manuscript has been accepted for publication and will be published January 2009.

Related Publications

  • Books
    • Kendall, K. C. and K. S. McKelvey. 2008. Hair Collection. In R. Long, P. MacKay, J. Ray, and W. Zielinski, editors. Noninvasive Survey Methods for North American Carnivores. Island Press. Washington, D.C. PDF version (800KB)
  • Journal Articles
    • Kendall, K. C., J. B. Stetz, J. Boulanger, A. C. Macleod, D. Paetkau, and G. C. White. 2009. Demography and genetic structure of a recovering brown bear population. Journal of Wildlife Management. 73 (1):3-17.[abstract]
  • View All Publications - html or pdf- (Books, Journal Articles, Presentations, Reports, Workshops, Magazine, Newspaper, Newsletter, Television, Radio, Film, Podcast Products)


Related Materials

Related Projects

  • Greater Glacier Bear DNA Project (1997-2002): project website
  • Use of Remote Camera Systems: Remote video and still cameras were used to: investigate how grizzly bears, black bears, and other wildlife species respond to baited, barbed wire hair traps; bear use of naturally-occurring bear rubs, bear marking behavior, and effects of putting barbed wire on bear rubs to facilitate hair collection; how hair traps may be modified to improve detection probabilities. Use of remote camera systems to investigate efficiency of DNA-based sampling methods

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Also visit the National Park Service's Glacier National Park official website to learn more about park activities.