BILLINGS, Mont. -- Wildlife agencies in the Northern Rockies go to lengths to warn people of the dangers of grizzly country -- from signs advising hikers to carry mace-like bear spray to radio ads that warn hunters to take care when stalking elk in bear habitat.

But after two hikers were fatally mauled in Yellowstone National Park over the summer, officials acknowledge their drive to make visitors "bear aware" is not reaching everyone. As a result, park officials, bear biologists and others say that in coming months they plan to sharpen a bear safety message that was already under review in hopes of preventing future maulings.

"We thought we were doing pretty good," said park biologist Kerry Gunther, pointing to a 30-year average of one bear-caused human injury in Yellowstone. "Maybe we were getting lucky."

Many bear education campaigns focus on saving the animals themselves, part of a broader effort to recover a species once nearly wiped out by hunting and other pressures. Slogans such as "a fed bear is a dead bear" highlight the increased likelihood of bears becoming nuisances -- and getting euthanized -- if they get used to eating human food or garbage.

With the success of the recovery efforts, Yellowstone's grizzly population has now grown to about 600 bears. Those animals are pushing into new areas of Montana, Wyoming and Idaho, forcing agencies to broaden the public safety side of their message.

Also growing is the size of the crowd that message needs to reach: Yellowstone National Park last year hosted a record 3.6 million visitors, and millions more visited five adjacent national forests and Grand Teton National Park.

Among some of those visitors, said University of Wyoming sociology professor Patricia Taylor, "there isn't a real fear of bears or appreciation of how strong they are."

"People will say, 'We want a bear to come to the campground. We want to see it,' " she said.

Both victims of this summer's mauling deaths had visited the park previously.

Among the advice commonly offered is to travel in groups, make noise while hiking and carry bear spray -- and know how and when to use it.

By contrast, one of the summer mauling victims was alone. Neither was carrying bear spray. And in one case investigators said the victim and his wife may have triggered the attack when they ran, yelling, from an approaching mother grizzly with cubs.