Hair rub technique appears to yield cheaper, more accurate data on grizzlies
Tuesday, April 27, 2010; 11:23 AM
In the year of the census, Montana's grizzly bears are standing up -- or, rather, shinnying up against trees -- to be counted.
The hair that grizzlies leave on trunks and branches acts as a kind of genetic calling card, and scientists have been gathering it, strand by strand, to track the threatened species' population trends. This new high-tech kind of bear hunt is preferable to the conventional radio collars and baited hair traps because it is cheaper and less risky -- for scientists and bears alike.
Collaring a bear is fraught with obvious dangers, and hair traps, which involve dousing wood with a pungent mixture of rotten fish and cattle blood, are time-consuming and expensive to make, maintain, check and move around so that bears don't avoid them over time when they realize there is no actual food.
"The great thing about bear rubs is you aren't asking the bear to do anything it's not normally doing. They're just rubbing all the time," said U.S. Geological Survey research scientist Katherine Kendall. The process of rubbing, she explains, is a form of chemical communication that bears use to mark their territory. "You get very precise estimates of trends. That's difficult to do with bears."
The work of the scientists who are analyzing the genetic material contained in ursine hair --their findings are being published Tuesday in the Journal of Wildlife Management -- provides an unexpected coda to a signature punch line of Sen. John McCain's (R-Ariz.) 2008 presidential bid.
For years, McCain has mocked the research of Kendall -- who received $4.8 million through the appropriations process to track grizzlies in the 7.8-million-acre Northern Continental Divide Ecosystem for a study conducted between 2003 and 2008. His criticism peaked during the 2008 campaign, when he ran a commercial calling the earmark "unbelievable."
Now Kendall and two colleagues have published a paper suggesting that recovering bear hair from trees can provide an accurate and cost-effective picture of how grizzlies are doing--and that the population in northern Montana is doing better than researchers originally estimated.
Scientists can monitor 10 times as many bears through rub samples as through radio collars, Kendall estimated. And the rubs provide far more accurate data than the sight checks that had served as the basis for past population estimates, in which researchers extrapolated the total population count from the number of females with cubs they saw in the area.
Although radio telemetry provides a precise account of a bear's fate--scientists can learn where the animal moves, whether it has cubs and at what point it dies--it is costly in addition to being risky. And the hair traps take extensive work to prepare as well as to deploy and maintain.
Christopher Servheen, who has served as the U.S. Fish and Wildlife Service's grizzly bear recovery coordinator for the entire 29 years of the program's existence, said the new analysis gives managers more confidence in the data they've already culled from hair traps and radio collars.
"How do we get the highest level of confidence with the smallest amount of money? That's our challenge, and it's not always easy," said Servheen, co-author of the Journal of Wildlife Management paper along with Kendall and its lead author, University of Montana graduate student Jeffrey Stetz.
Stetz and his colleagues analyzed 13,000 genetic samples culled from four years of bear rubs, from 1998 to 2000 and 2004. They also looked at 21,000 samples collected from hair traps. Their findings, coupled with the genetic analysis stemming from Kendall's study, suggest there are roughly 765 grizzlies in the Northern Continental Divide Ecosystem-- 2 1/2 times as many as the initial estimate.