Now Mr. Gaines is leading the most ambitious effort ever to document whether grizzlies still exist here  a century after fur trappers and ranchers killed them off by the hundreds  at a time when tension is high in the West over the fate of wild predators like gray wolves. While many people want the grizzlies, an endangered species, to make a comeback here, others worry that more bears will mean more conflict.

“Grizzlies are a threat to livestock and to humans,” said John Stuhlmiller, the director of government relations at the Washington State Farm Bureau. “People might think they’re neat and they might want to go see them in the zoo, but in the wild they’re not a friendly, cuddly creature.”

People whose livelihoods are not threatened by predators do not get it, Mr. Stuhlmiller said. “If my 401(k) was being raided by grizzly bears, I would think differently,” he said.

For nearly 30 years the federal government has had a program to help restore the grizzly bear population in Idaho, Montana, Washington and Wyoming. It has made a difference in places like Yellowstone National Park and the Continental Divide region of Montana, but not in the North Cascades, one of six designated recovery zones. Instead, this area has been locked in a virtual standstill as political winds shift over the preservation of large predators.

Grizzlies were named a protected species in 1975. Under protection, their population tripled in parts of the Rockies and by 2007, they were removed from the list. But last September, a federal judge in Montana ordered grizzlies back on, citing threats that included changes to their habitat caused by climate change.