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

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

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):

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]