Griz study relies on rub trees
A new and expansive effort to monitor the Northern Continental Divide's grizzly bear population will capitalize on a creature comfort for bears: the irresistible urge to scratch their backs on trees.
The research project mainly will be aimed at determining whether collecting hair samples from rub trees over three successive years can provide a reliable measure of whether the region's grizzly population is stable, growing or shrinking.
It will be led by Kate Kendall, the U.S. Geological Survey scientist who spearheaded two previous grizzly bear population studies based on genetic analysis of bear hair.
A study conducted in 1998 and 2000 generated a population estimate for the greater Glacier National Park area and a 2004 study produced a population estimate for a sprawling, 8 million-acre area that encompassed Glacier, the Bob Marshall Wilderness Complex and surrounding grizzly bear habitat.
The 2004 project provided a snapshot population estimate of 765 grizzly bears for the entire Northern Continental Divide Ecosystem. It was unprecedented in its scope, involving an army of more than 400 people to collect more than 34,000 bear hair samples.
Most samples were collected by scent-baited sites surrounded by a strand of barbed wire, but a good portion of the sample were collected from trees, telephone poles and sign posts that bears return to repeatedly for back-scratching relief.
The new study, to get under way next week, will make use of those known rub stops to collect as many hair samples as possible over the next three years, Kendall said.
Logistically, it will be far less complicated and less expensive than the 2004 project, relying on a crew of just 15 people who will essentially be professional hikers and hair gatherers over the next few months. The work will be confined to rub trees on trails and roads and power lines, and the hair gatherers won't have to carry barbed wire and extremely foul-smelling scent lure.
"There is no lure so that's nice, just not having to carry around stinky stuff and lots of weight," said Kendall, who first sensed the scientific potential of rub trees soon after she started working in Glacier in 1983.
Back then, Kendall organized a group of 15 students and instructors to survey the park's trail system for bear sign, and what they found over time was an extensive network of rub trees.
"We did it every fall for years," she said.
By 1998, after the development of genetic recent technology, the trail survey provided a reliable inventory of rub trees during the Glacier Park grizzly bear population study.
Rub tree samples collected during the 2004 field work were responsible for detecting 53 percent of males and 26 percent of females in about 80 percent of the ecosystem. Rub-tree collections were not conducted on the entire Rocky Mountain Front because of budget constraints.
"In this new study we feel confident we'll improve those numbers' because there will be an effort to locate rub trees on the East Front, Kendall said.
Nearly 4,800 rub locations were monitored in 2004, and the new study likely will involve more than 5,000, said Kendall, who estimates that the effort will detect a minimum of at least 300 bears annually.
As the study progresses, it will detect many of the same bears, providing a 'recapture" rate that can be applied in statistical modeling to produce a population trend estimate.
Kendall's lead research assistant, Jeff Stetz, explored the statistical modeling for his master's thesis. Stetz found, on paper, that the work will 'reliably detect with a high degree of precision" a minimum 3 percent decline, as well as population increases, within three years.
The field work will put the thesis to a test.
Montana Fish, Wildlife and Parks, meanwhile, is several years into a study using the tried and proven method of radio-collaring female grizzly bears and monitoring birth and death rates to provide a population trend estimate.
"This is a research project to explore whether we can monitor trend just using hair collection, as potentially a complement to or an alternative to radio telemetry trend monitoring," Kendall said. "This is really research aimed at exploring how well a different sampling approach will work to monitor trend."
The project is expected to cost roughly $250,000 in the start-up year, with the money coming from a variety of grant sources.
That's well below the $4.8 million cost of the far more logistically challenging 2004 study. After the first year, Kendall said the work will likely cost less because of the strong potential to enlist park and wilderness rangers, trail crews and volunteers for bear-hair collection.
Reporter Jim Mann may be reached at 758-4407 or by e-mail at jmann@dailyinterlake.com