The mauling occurred just after Yellowstone's peak weekend for tourism. While lamenting the death, officials said they didn't want to overemphasize the danger to visitors.
"This is a wild and natural park," said Diane Shober, director of the state Wyoming Travel and Tourism agency. "At the same time, the likelihood of this happening again is small."
It was the park's first fatal grizzly mauling since 1986, but the third in the Yellowstone region in just over a year amid ever-growing numbers of grizzlies and tourists roaming the same wild landscape of scalding-hot geysers and sweeping mountain vistas.
The bear attacked Wednesday morning to defend against a perceived threat, park officials said. The wife of the victim called 911 on her cell phone and other hikers in the area responded to her cries for help.
Nash said the couple saw the bear twice on their hike. The first time, they continued hiking. The second time, the grizzly charged them and the man told his wife to run.
The woman told park officials she didn't see the bear attack her husband. When the bear went for her, Nash said, she dropped to the ground. The grizzly lifted her off the ground by the day pack she was wearing, then dropped her. The woman may have had scrapes and bruises but didn't seek medical attention.
Yellowstone and surrounding areas are home at least 600 grizzlies -- and some say more than 1,000. Once rare to behold, grizzlies have become an almost routine cause of curious tourists lining up at Yellowstone's roadsides at the height of summer season.
Those tourists have been flooding into Yellowstone in record numbers: 3.6 million last year, up 10 percent from 2009's 3.3 million, also a record.
In June 2010, a grizzly just released after being tranquilized for study killed an Illinois man hiking outside Yellowstone's east gate. Last July, a grizzly killed a Michigan man and injured two others in a nighttime campground rampage near Cooke City, Mont., northeast of the park.
Full-grown Yellowstone bears can stand 6 feet tall and top 600 pounds. They have been known to peel off a man's face with a single swipe of their massive, clawed paws.
They are an omnivorous species with a diet of berries, elk, fish, moths, ants and even pine nuts. In 2009, a federal judge restored threatened species protections for Yellowstone grizzlies, citing beetle-caused declines in the numbers of whitebark pine trees in the region. The protections had been lifted in 2007.
Environmentalists have cited the beetle-caused decimation of the whitebark pine as putting grizzlies in greater danger of extinction because some bears rely on whitebark pine nuts. But experts caution that it sometimes can be impossible to determine the cause of bear attacks on humans.
Grizzlies require constant vigilance for tourists and park employees alike, said Caleb Platt, a service station manager at Canyon Village. Platt said he has had a handful of fairly close encounters with grizzlies while hiking in the park.
"When it's close and you realize it does see you, it gets the heart racing," Platt said.
Park officials worked to clear the area near Wednesday's attack of people. A warning sign was posted on the trailhead, Nash said.
"It is in the backcountry of the park, and we have access challenges and limited communication," he said.
Officials also issued recommendations for visitors to stay safe from backcountry bears: Stay on designated trails, hike in groups of three or more, and make noise in places where a grizzly could be lurking. Bear spray -- pressurized hot-pepper residue in a can -- is effective in stopping aggressive bears, they said.
A spokesman for the Wyoming state tourism agency doubted the attack would cause anybody to change their Yellowstone vacation plans.
"What has happened here hasn't happened for a quarter century," Chuck Coon said. "It is very sad, though, and I'm very sorry to hear of it."
Associated Press writers Ben Neary and Mead Gruver contributed to this report from Cheyenne, Wyo.