A grizzly bear walks across in Yellowstone Park. (David Grubbs, Billings…)
A grizzly fatally mauled a hiker in Yellowstone National Park on Wednesday when he and his wife surprised the bear and her cubs — the first such killing in 25 years.
The couple were on the popular Wapiti Lake trail when they encountered the bears, park officials said in a statement. The sow apparently perceived them as a threat to her cubs and attacked the man.
Nearby hikers heard the woman's cries and used a cellphone to call for help, officials said. The man died at the scene. His wife was unhurt.
Park officials said the hiker's identity and hometown would not be disclosed until Thursday, after his family had been notified.
Rangers closed all trails and backcountry campsites in the area, which is southeast of Canyon Village, and walked through to clear out any other hikers or campers.
The trail is a gateway to the Pelican Valley area, where bears are commonly seen. A bear warning sign was posted at the trailhead.
Yellowstone spokesman Al Nash said there had been no reports this year of grizzly encounters in the park, which is just emerging from a heavy winter.
"This is the first bear-caused human fatality in Yellowstone since 1986," park officials said in the statement.
However, two people were killed nearby last summer. In June, a grizzly that had been trapped for study and released killed a hiker outside the park's east gate. And in July, a grizzly with her cubs invaded a campground at night, killing one camper and injuring two others near Cooke City, Mont., north of the park.
Wildlife researchers in the upper Rockies have theorized that with declining grizzly habitat and fewer food sources, bears might become more prone to attack humans. But Wednesday's incident appeared to be an act of defense by the bear, which fled with her cubs.
If the park investigation supports the conclusion that the sow behaved normally, she will not be killed, park spokeswoman Linda Miller told Reuters.
The last fatal grizzly attack in Yellowstone was in October 1986, when the mauled body of a man was found by the road near Otter Creek. A camera and tripod were nearby, causing park officials to conclude that he was attacked while photographing a grizzly.