Sometime around the second week of August, an injured bison was seen walking into the Yellowstone River upstream of the LeHardy Rapids. The bison was reported to have a large abscessed wound near his rear. The annual bison rut occurs about this time, so perhaps this animal was injured in a mating tussle.
So the bison walked into the river and did not come out. Its body was trapped beneath the water and untouched by other animals for reportedly 8 days. By that point the carcass was bloating and came to the surface. It ended up along the eastern edge of the Yellowstone River at LeHardy Rapids. Two separate grizzly bears found their way to the carcass. Reportedly on the evening of August 23, the larger grizzly chased off the other bear and claimed the feast as his own.
I watched this cycle of nature for the next two days. The video below is from August 24. During the morning, the light was harsh and the bear is shadowed. But it was still an amazing sight. Over the day, the bear would eat for usually more than an hour at a time, then climb up hill a short distance to sleep in the trees. I inferred he was going up hill so that he could more easily hear over the roaring rapids if the other grizzly was returning to the carcass. He would generally sleep a couple of hours, then return to the river, sometimes just for a drink, and sometimes to eat some more. By the evening of August 24, the big bear seemed no longer concerned with a threat from the other bear. He was definitely noticing the growing crowd on the west bank of the river. And as night fell, the big guy plopped down in the river on the carcass to sleep.