A group of hikers came across the grizzly eating a carcass 10 days ago, which turned out to be a black bear.
"We closed the trail immediately," said Steve Michel, a human-wildlife conflict specialist with Banff National Park.- Hear his full interview with the Calgary Eyeopener by clicking on the "Listen" button above.
Michel said he knows of four other instances when a grizzly has hunted, killed and eaten a black bear in Banff.
"It may not be as rare as we think it is," he said. "But it is rare that we actually are able to document it. We tend not to know about it all."
Michel said he suspects the kill was opportunistic.
"Grizzly bears are opportunistic hunters," he said. "They will take advantage of any food source that presents itself."
The grizzly that ate the black bear on the Sundance Canyon trail is known to conservation officers. It has been handled and radio collared in the past.
The bear is known as Grizzly Bear No. 122.
Largest bear in area
"Bear 122 is the largest, most dominant grizzly bear on the landscape," the park official said. "Last fall, I would estimate his weight at 650 to 700 pounds, which is enormous for the Rocky Mountains — about as big as grizzly bears get around here."
Michel said the black bear was likely a fifth the size of the grizzly.
"We know it's a dog-eat-dog world out there, but we're finding out it's a bear-eat-bear world as well," he joked.
Right now, it is buffalo berry feeding season in the Rockies, which is the most important time of the year for grizzlies.
"They need to put on weight before the fall," Michel said.
Michel also warned there is increased potential for surprise encounters between bears and humans around now because bears are feeding on buffalo berry patches near populated areas.
Campsites at the Crandell Mountain Campground were closed to tents this week in Waterton Lakes National Park, in southern Alberta, because of bear activity in the area.
Officials said the berry patches are drawing the animals in, but some bears have also wandered into campsites and tents looking for food.
Parks Canada has been trying to deter the bears, including stripping nearby bushes of berries, but the the agency said that isn't working.
People with hard-top campers and trailers are still allowed in the area. There was no word on when the restrictions will be lifted.