U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2010–3054

September 2010 Printed on recycled paper

The U.S. Geological Survey began a grizzly bear research project in 2009 in the Northern Continental Divide Ecosystem 

(NCDE) of northwestern Montana. This work uses hair collection and DNA analysis methods similar to those used in the 

2004 Northern Divide Grizzly Bear Project. However, instead of producing a snapshot of population size, the objectives of 

this new work are to estimate population growth rates by collecting hair at natural bear rubs along trails, roads, and fence 

and power lines. This approach holds promise of providing reliable estimates of population trends in an efficient, costeffective, and unobtrusive way. 

Bear rubs and other passive hair-collection opportunities occur on all types of lands found in the NCDE: forest and 

prairie, public and private, front and back country. Bear rubs are 

found by hiking forest trails, roads, and power and fence lines. 

Short pieces of barbed wire were attached to the rubbed surface 

to facilitate hair collection at most sites; however, barbless wire 

is used on trees bumped by pack animals. No lure or attractants 

were used to attract bears to these sites. Genetic analysis of 

the hair reveals the species, sex, and individual identity of the 

bears using rub trees. We use this information in mark-recapture 

models to estimate population growth and survival rates, along 

with other valuable information. 

MONTANA

IDAHO WYOMING

BRITISH

COLUMBIA ALBERTA SASKATCHEWAN

Study Area

Study area boundary

Highways

2009 bear rub

 sites

EXPLANATION

Noninvasive Grizzly Bear 

Monitoring Project 

2009

0 12.5 25 50 75 Kilometers

Noninvasive Methods for Monitoring

Bear Population Trends

We conducted field work from mid-May into early October in 

our 8.5-million-acre study area in 2009. We identified 4,907 bear 

rubs from which we collected 9,240 bear hair samples. Genetic 

analysis identified 258 individual grizzlies that had deposited 

the hair. Field work will continue through 2011. An evaluation 

of the effectiveness of monitoring bear population trend using 

this approach will be conducted in 2012.

2009 Update

Timeline 2009 2010 2011 2012

Identify/setup bear rubs

Hair collection

Genetic/data analysis

Prepare manuscript
Surveying bear rubs is safe, efficient, and 

consistent with wilderness “minimum 

tool” requirements. Further, no trapping 

or overflights are required, surveys 

can be conducted on established 

travel routes, grizzlies and black bears 

are sampled concurrently, and bear 

behavior is not affected by the presence 

of bait or lure. Because field sampling 

methods require little training and 

experience, there is potential to reduce 

monitoring costs through assistance 

by existing agency personnel and 

volunteers. Remote camera footage of 

bears at rub trees can be viewed on the 

USGS Web site:

http://www.nrmsc.usgs.gov/research/

KendallRemoteCamera.htm

For more information, please visit the project’s Web site: http://www.nrmsc.usgs.gov/research/NGSbear_monitoring.htm

Our previous work demonstrated 

that collecting hair from bear rubs can 

sample a large portion of the population. 

In 2004, nearly 13,000 hair samples were 

collected from 4,795 bear rubs. From 

these samples, we detected more than 

50 percent of the males and more than 

25 percent of the female grizzlies in the 

population. This was despite not being 

able to conduct sampling on 20 percent 

of the NCDE and not sampling in late 

summer when female rubbing behavior 

peaks. We can use these detections to 

look at fine-scale patterns in this population, including changes in how bears are 

distributed on the landscape, and if there 

are any barriers to interbreeding (that is, 

geneflow) within the NCDE. By surveying bear rubs throughout occupied range 

and over a longer sampling season, we 

expect to detect even more grizzlies than 

the 275 individuals detected at bear rubs 

during 2004 once a sampling network 

is established. More detections allow us 

to make more reliable inferences about 

how this population is faring and assess 

progress toward recovery.