Grizzly DNA study estimated at $1 million-plus
by Brent Shrum, Kootenai Valley Record
February 3, 2011
A grizzly bear DNA study similar to one that revealed more than twice as many bears living in Glacier National Park and the Bob Marshall Wilderness would likely cost a little over $1 million to replicate in the Cabinet-Yaak ecosystem, according to researcher Kate Kendall of the U.S. Geological Survey.
Kendall provided an overview of her 2003-2004 study during a meeting last week in Libby sponsored by Lincoln County. According to Commissioner Tony Berget, there could be enough interest to fund such a study locally through a cooperative effort. Participants could include Lincoln and Sanders counties, Boundary County in Idaho and Revett Minerals and Mines Management, Berget said.
Kendall’s study focused on an intensive effort to snag bear hair from baited traps strung with barbed wire. More than 640 grid cells measuring 7x7 kilometers each were laid out over the study area, with a trap in each cell collecting samples over four 14-day sessions. Traps were moved between sessions.
The study collected nearly 21,000 samples through the hair traps, and another 13,000 were taken from naturally occurring rub sites. The 34,000 samples, containing hair from both black and grizzly bears, subjected to DNA analysis that detected 545 unique grizzly bears.
"But we know we didn’t sample them all," Kendall said. "You don’t expect to when you’re sampling like this, unless you’re sampling a whole lot more intensely than we did."
The number of bears confirmed by the hair samples was added to another 18 bears known to be in the area but not detected by the traps, and a statistical formula was applied to estimate the number of other bears likely to have gone undetected for a total estimated population of 765 grizzlies in the ecosystem. That number could range from a low of 715 bears to a high of 831 with a 95 percent confidence level, Kendall said.
Those numbers are about two and a half times higher than previous estimates based on sightings of sows with cubs, Kendall said.
The study also looked at genetic links between bears in different parts of the study area to determine if there were barriers to movement of the animals. Some impact was seen along the Highway 2 corridor in the western part of the study area. While the highway itself may not have been a deterrent to movement of the bears, "lethal attractants" associated with development may have been leading to the death of grizzlies before they had a chance to breed, Kendall said.
"It’s like a warning sign that if we don’t try to mitigate this impact, it will start to fracture this population," she said.
A similar study in the Cabinet-Yaak ecosystem would be complicated by the smaller bear population, estimated at around 50 to 60 animals. A smaller population requires more effort for an accurate study, Kendall said.
"That’s going to be a challenge here," she said.
Kendall proposed that such a study would need smaller grids than those used in the Glacier-Bob Marshall study. Using 5x5 kilometer grids would result in 269 cells. Kendall also proposed five sampling sessions rather than four.
The study would require 19 two-person crews to maintain the hair traps and collect additional samples from natural rub sites.
Kendall estimated that the total cost of the study, including setup, collection and analysis, would be around $1,147,000.
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Editor's Note: See the February 1, 2011 edition of the Kootenai Valley Record for the printed version of this story. The Kootenai Valley Record publishes once a week, on Tuesdays, in Libby, Montana. They are a locally owned community newspaper, located at 403 Mineral Avenue in Libby. For in-county and out-of-county subscription information, call 406-293-2424, or e-mail kvrecord@gmail.com.
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