Forgive Jeffrey Stetz and his colleagues for preferring to not capture grizzly bears, radio-collar them, and then fly around in search of offspring to estimate changes in northwest Montana's grizzly population. They'd much rather collect and analyze the hair the bears leave behind when they rub against trees, power poles and fence posts.
Turns out, this noninvasive method for measuring population trends might not only be safer—for bears and researchers alike—but potentially more efficient and more accurate.
Stetz, a doctorate candidate with the Montana Cooperative Wildlife Research Unit at the University of Montana, served as the lead author of a study published last week in the Journal of Wildlife Management suggesting that bear rub surveys represent a complement, and possible alternative, to traditional telemetry-based methods for monitoring population trends.
- Photo courtesy Jeffrey Stetz & Amy Macleod
- A grizzly bear rubs against a tree in Glacier National Park, leaving behind hair samples that give researchers a new and noninvasive way to estimate changes in northwest Montana’s grizzly population.
"Our study," Stetz says, "is saying that when you monitor an adequate number of these bear rubs"—in their case some 4,900 last year—"and then genotype even a small subset of the samples...that there is enough power to make very precise estimates of growth rates."
"It's pretty much unheard of, as far as the precision of those estimates," he says.
But so far those estimated growth rates are only based on simulations. The full three-year study won't be completed, and the growth rate known, until the end of 2011. (It's expected to be between 2 and 3 percent.) Still, Stetz and his research partners—Katherine Kendall of the U.S. Geological Survey's Northern Rocky Mountain Science Center and Chris Servheen, the U.S. Fish & Wildlife Service's (FWS) long-time grizzly bear recovery coordinator—believe the results so far show promise.
"I think it has the potential to inform management, to track the successes or failures of the conservation strategies being developed by FWS and other agencies," Stetz says.
The research piggybacks on previous work famously pilloried by Sen. John McCain, R-Ariz., as pork barrel spending. Between 2003 and 2008 a Kendall-led research team received about $4.5 million—largely thanks to appropriations secured by former Sen. Conrad Burns, R-Mont.—to analyze hair samples. The project aimed to estimate the grizzly bear population in the 7.8 million-acre Northern Continental Divide Ecosystem, which stretches from north of Missoula to the Canadian border. On the presidential campaign trail in 2008 McCain called the earmark to study grizzly DNA "unbelievable," and often joked, "I don't know if it was a paternity issue or a criminal issue."
Despite McCain's political put-downs, Kendall's study, published in 2008, yielded the best estimate yet of how many grizzlies roam the area—765, based on the 2004 data, more than twice FWS's previous estimate. Biologists suspect that number is even higher now.
Today, Stetz's work uses the same hair sample data to measure grizzlies' growth rate that Kendall used to measure abundance. And the data McCain criticized for its cost may ultimately (and ironically) end up saving money.
"There's the potential for our method to be more affordable [than trapping and tracking]," Stetz says, "because we can enlist park rangers or trail crews or people working in the wilderness and volunteer groups. They can be trained easily to do this work and still maintain the scientific rigor that's needed for this kind of application."
Stetz's paper came the same week that Rick Mace, a biologist with Montana Fish, Wildlife and Parks, presented his finding that the grizzly bear population in the Northern Rockies is growing at a rate of about 3 percent per year. Mace and his research team trapped and tracked dozens of female grizzlies and watched their movements in real-time using GPS technology. Stetz says that the two studies together, while they differ in approach and scope, "are far stronger than either alone."
"I think this is a really unique opportunity to have two complementary projects—same system, different methods, same question—and to see how these respective methods work," Stetz says. "That rarely happens, if ever."
Stetz and Mace both credit the grizzly bear population's growth to a number of things, including habitat protections and public education.
"It's hard to say what the most important thing is," Stetz says, "but [wildlife managers] have really, I think, made the social carrying capacity far greater than it ever used to be, just by keeping us out of conflict, and then dealing with it when there is [conflict]."
As grizzly population estimates become more exact and growth rates climb, some hope the trends portend the removal of Ursus arctos horribilis from the endangered species list, where it's been designated as "threatened" since 1975. (Yellowstone National Park's grizzlies were delisted in 2007, but U.S. District Judge Donald Molloy of Missoula relisted them last year.)
Stetz's study itself doesn't bolster the case for delisting, but more exact science brings more certainty to whatever management decisions are made.
"Our challenge is always to balance precision with cost," says Servheen. "It would be great to be able to estimate the population each year with very high precision, but we don't have the money for that. No one has the money for that. So what we have to do is come up with ways that allow us to manage the population with reasonable certainty within the budgets available to us."
As for the attention McCain brought to the genetic analysis of grizzlies, Stetz says it only helped.
"I can't say enough about how this was a collaborative effort," he says, "so when he pointed a finger to us as an example of wasteful spending, I think instead it backfired on him, while it brought a lot of positive focus on a very well conducted project."