The Jackson Hole News & Guide  has an interesting write up on the interaction between wolves and grizzly bears in Yellowstone. Yellowstone presents an opportunity to study how two large carnivores battle over downed game. Interesting it turns out that wolves don't always lose to the much larger grizzly bear.
During confrontations between wolves and bears, especially over food, bears in Yellowstone win roughly 80 percent of the time, Smith said. In other places such as Banff National Park in Canada, bears win a carcass about 50 percent of the time. The reason for the discrepancy is unclear, Park wolf biologist Doug Smith said. It’s usually male grizzly bears that will claim a carcass from wolves. Researchers have documented up to 12, and perhaps as many as 20, grizzly bears on a single kill, with wolves typically hanging around the periphery as “bystanders,” Smith said.