Park spokesman Al Nash said Wednesday's mauling of the 57-year-old man was a purely defensive act. He said Yellowstone typically does not try to capture or remove a bear in what he called "a wildlife incident."
Wednesday's attack occurred about 1-1/2 miles up a popular backcountry trail and was the first fatal grizzly attack inside the park in 25 years — but the third in the Yellowstone region in just over a year.
The attack occurred not far from an area that is one of Yellowstone's top attractions, and busloads of tourists normally gather there to take in the view from Artist's Point, one of the park's most iconic.
A stunning waterfall drops hundreds of feet in the Grand Canyon of the Yellowstone, and trails along both canyon rims are normally crawling with tourists. Authorities closed the area but planned to reopen it in a few days, Nash said.
The identity of the 57-year-old victim was being withheld until his family could be notified. His wife escaped serious injury and no longer was at Yellowstone, park officials said. They declined to reveal her whereabouts.
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. She called 911 on her cell phone, and other hikers in the area responded to her cries for help.
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 and then dropped her.
The woman may have had scrapes and bruises but didn't seek medical attention. The man died at the scene, Nash said. "We observed both bite marks and claw marks," he said.
In this case, Nash said, park officials relied on the wife's account of the attack in deciding not to pursue the grizzly.
She told rescuers that the couple surprised the sow with her cubs — one of the most dangerous situations possible for humans encountering grizzlies.
Based on her account and understanding of grizzly behavior, rangers believe the bear instinctively charged to protect her young. The bear had never been documented before, never been tagged, and there was no reason to believe it had interacted with humans before, Nash said.
If so, the decision may very well have been different, he said.
"All indications are that this was a defensive attack," Nash said.
Nash said there is no way to definitely know what the bear was thinking or reacting to. He said the couple were day hikers and that it wasn't known if they were carrying bear spray, pressurized hot-pepper residue in a can that is effective in stopping aggressive bears.
The decision not to track and kill the bear isn't unprecedented.
In nearby Grand Teton National Park, officials decided not to intervene with a grizzly that wounded a man there in 2007.
Rangers determined that female was defending its cubs and didn't pose a general threat to humans. That atttack was considered natural behavior and officials didn't believe the bear was any more dangerous than any other sow grizzly in the region.
This summer, the same bear and her cubs have drawn crowds of tourists to roadsides in the park.
Yellowstone and surrounding areas are home to 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.
Barbara and Carl Waxman, Baltimore residents making their first trip to Yellowstone, were dismayed when they found their path to Artist's Point blocked by barricades in the aftermath of the mauling.
Avid photographers, they had hoped to shoot a lookout where they had read a stunning early-morning rainbow could be seen above the falls.
"It's like not being able to see the Mona Lisa," Barbara Waxman said. "If they gave me the option, I'd go to that point in a second, grizzly bear or no."
Some visitors said they didn't know about the attack. Tourists staying at a campground in nearby Canyon Village said no rangers or park personnel told them about it.
Nash said park officials didn't go campsite to campsite to warn visitors of the attack, but they did fly over the area by helicopter to ensure the area was clear.
"If we had any concerns for visitor safety we would take whatever measures would be necessary to protect them," he said.
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.
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.
Grizzlies 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.
Officials routinely urge visitors to take precautions: Stay on designated trails, carry bear spray, hike in groups of three or more, and make noise in places where a grizzly could be lurking.