BILLINGS, Mont. – Yellowstone’s grizzlies are going to be particularly hungry this fall, and that means more dangerous meetings with humans in a year that is already the area’s deadliest on record.

Scientists report that a favorite food of many bears, nuts from whitebark pine cones, is scarce. So as grizzlies look to put on some major pounds in preparation for the long winter ahead, scientists say, they will be looking for another source of protein – meat – and running into trouble along the way.

Wildlife managers already report bears coming down off the mountains and into areas frequented by hunters, berry pickers and hikers.

“Pack your bear spray: there’s going to be run-ins,” said grizzly researcher Chuck Schwartz with the U.S. Geological Survey.

Two people have been mauled to death by grizzlies this year in Wyoming and Montana. Experts said that’s the most in one year in at least a century for the Yellowstone region, which also includes parts of Idaho.

Yellowstone’s grizzlies were recently ordered back onto the threatened species list by a federal judge who cited in part a decline in whitebark pine. Beetles, apparently surviving winters in larger numbers because of less frequently freezing temperatures, have decimated vast stands of the high-altitude trees. In some areas studied by researchers, more than 70 percent of trees have been killed.

“Every year is now a bad year for whitebark pine,” said Louisa Wilcox with the Natural Resources Defense Council. “We can expect more conflicts and we are getting it.”

Government scientists said the two fatal maulings came too early in the year for pine to have played a role. Bears typically don’t start gorging themselves on the troves of pine nuts that are stashed by squirrels until mid-August.

But the attacks highlighted the hazards of a region that is home to an estimated 580 grizzlies and visited by more than 3 million people a year. And officials said the maulings should serve as a warning as bears begin to push to lower elevations. Adult males will need to gain on average 50 pounds in the next few months to last through the winter.

“Right now, every god-dang dead cow down in this country’s got grizzlies on them,” said Mark Bruscino, a bear specialist with the Wyoming Game and Fish Department in Cody. “We’ve already had a couple of reports of bears on the gut piles of hunter-killed elk. Road-killed deer have bears on them.”