The Future in “Bear hair”: Will Noninvasive DNA Sampling Advances Minimize the Need to Capture & Handle Bears for Management & Research?

by | Oct 12, 2020

Dear colleagues,  I am honored to have Tyler Brasington bring his field experience and knowledge to this blog as he writes about non-invasive grizzly research.  Thank you, Tyler!”  Dr. Mark

Capturing and chemically immobilizing bears is stressful for the animal. Therefore, it is imperative that researchers and managers justify all capture events, thoroughly evaluating potential alternatives to a hands-on approach.1, 8, 9 In some cases, the information required to meet management and research objectives can only be obtained through capture and handling (i.e., deployment of radio/GPS collars for monitoring). However, if research questions and objectives can be answered using alternative, noninvasive methods, researchers should think about using these approaches first.6 The goal of this summary is to highlight new and developing non-invasive technologies and techniques which may offer broader applicability, better efficiency and effectiveness, and address multiple research questions simultaneously,13 while reducing the need to capture and handle bears in the field.

Grizzly bear rubbing on tree

Grizzly bear rubbing on tree

Capture and handling methods (i.e., deployment of radio/GPS collars) allow researchers to address questions surrounding the overall health of a population by drawing blood for complete blood count (CBC) generally reflecting the bears health and condition at the time of capture, disease analysis, tick borne diseases, cub survival, and causes of mortality. Collaring bears also offers the opportunity to answer spatially driven questions surrounding habitat preference and movements. Unfortunately, genetic sampling furnishes no details on age, reproductive status, body condition, daily movement patterns, or habitat use.10 Hair and scat sampling are two of the most common methods for obtaining DNA. Hair snare sampling is conducted employing a hair collection device, or a series of devices which include but are not limited to barbed wire, glue, adhesives, brushes, corrals, cubbies, using two approaches, baited or passive methods.2, 3, 10, 15, 16 These devices are positioned in a sampling framework, or study grid. For hair sampling to be successful, the devices deployed in the field must promote use by the animal. Population estimates have historically relied on observations and counting bears on the landscape.11 The downside to this method is that bears may be counted more than once, or maybe not at all. Genetic sampling can provide an accurate and precise estimates of population size, however, this is usually years after the hair has been collected due to processing time required to extract DNA from hair samples. Even then, these population estimates are only considered a snapshot in time. Despite the non-invasive nature of genetic sampling, some species may avoid hair corrals and cubbies due to human odors. While genetic analysis via means of hair collection is generally expensive, it is extremely reliable.9 Hair DNA also experiences less degradation than scat, inherently producing more consistent results at a lower cost.10

Greater Glacier Bear DNA Project, Montana (1997-2002):

One of the better-known projects using genetic analysis and DNA hair samples was the Greater Glacier Bear DNA Project (1997-2002) led by USGS research scientist Katherine Kendall. One of the project’s significant accomplishments was estimating the average number of grizzly bears in their particular study area, calculating density inside Glacier National Park (1998: n = 240.7, 95% CI= 202-303; 2000: n = 240.6, 95% CI= 205-304).9 They found that the average density was 30 bears/1000 km2. This study included two types of noninvasive genetic sampling techniques: hair snags (baited) and rub trees (passive); which increased their sample coverage and helped improve population estimates.  

Grand Teton National Park, Wyoming (2014-2015):

Hair Snag Sample

Hair Snag Sample

Researchers from the USGS Interagency Grizzly Bear Study Team (IGBST), Grand Teton National Park, and Wyoming Game and Fish sought to better understand how grizzly bears respond to the elk harvest during the Elk Reduction Program (ERP). They used methods outlined by Kendall & McKelvey 2008 and Kendall et al. 2009 for active and passive sampling. During their study (2014-2015), they successfully identified 31 grizzly bears (6 females, 25 males) via genetic hair sampling. The data acquired during their study informed crucial management decisions by suggesting that the late timing of the elk hunt helps limit the use of elk remains/carcasses to a small number of resident grizzly bears.17

As advances in genetic techniques continue, more research projects have the option to utilize non-invasive genetic sampling techniques. Examples of recent advances include several studies analyzing reproductive hormone levels, and stress levels using grizzly bear hair collected via hair snags.4, 5, 12, 14

One specific study in British Columbia5 found that if grizzly bears in the region do not obtain enough salmon, they may exhibit chronically elevated cortisol and testosterone levels through increased nutritional and social stress.

The general consensus amongst wildlife professionals is that before using physical capture and handling, there should be a thorough evaluation of potential alternatives to a hands-on approach, such as non-invasive sampling (i.e., scat & hair sampling).1, 6, 7, 8  While non-invasive sampling provides an opportunity to limit handling and capture events, producing precise and accurate estimates of population, further research is needed to improve current techniques and methods, as they are time intensive, and genetic population estimates only represent only a snapshot in time. [Works Cited]

Tyler Brasington is a current graduate student at the University of Wisconsin-Stevens Point. His research and work has focused on the ecology, biology, management of grizzly bears, and attitudes and perceptions of bear management. Tyler has worked seasonally in Grand Teton National Park since 2017, and is currently a wildlife management ranger for the Bear Management Office. Tyler received his B.S. in Environmental Science from the University of Wisconsin – Whitewater. Tyler maintains the awesome website:
Tyler Brasington

Tyler Brasington

Mark R. Johnson, DVM

Meet Mark R. Johnson, DVM

Wildlife Veterinarian, Instructor, and CEO of Global Wildlife Resources


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