The last time the Corps saw a grizzly east of the Rockies in 1805 was on the lower Jefferson River near the Three Forks. They saw no bears in the Lemhi, Salmon, or Bitterroot river valleys along the east side of the Bitterroot Range, nor on the Indian trail over the mountains. They noticed some bear sign in the vicinity of Celilo Falls in October of 1805, and came upon some tracks in the vicinity of Fort Clatsop that winter, but made no mention of which species had made them.
Nonetheless, in February of 1806 Captain Lewis felt himself ready to summarize what he had so far discovered about four-legged animals in the Northwest. He wrote:
And so on, devoting most of his remaining 800 words that day, February 15, to a discourse on Indian horses and mules.
On the 16th he wrote briefly of the Indian dog, then continued his remarks on the grizzly.
It wasn't until they got back to the west slope of the Bitterroot Range in May that Lewis had occasion to expand on those conclusions. During their month-long residence at "Camp Chopunnish" (see map)
near the Nez Perce chief Twisted Hair's village on the Clearwater, while waiting for snow to melt among the peaks and ridges of the Bitterroots, bear meat became a staple in their diet, the spring chinook salmon run wasn't due in for several more weeks. They killed at least seven grizzlies
On May 15, after the hunters brought in two brown bears that Private John Collins had bagged, and three that Private François Labiche had killed, Lewis observed,
By the end of the month, Lewis turned to the Indians for their knowledge and experience; they called the grizzly Ho-host, or white bear, and the black bear Yâck-kâh. "This distinction of the Indians," said Lewis, "induced us to make further enquiry relative to their opinions of the several species of bear in this country."
"The white and the grizzly of this neighbourhood are the same of those found on the upper portion of the Missouri," Lewis concluded, but he decided that they were not as ferocious as the grizzlies of the Missouri because they fed mainly on roots rather than on live animals such as bison. "They have attacked and faught our hunters already, but not so fiercely as those of the Missouri." Nevertheless, the hunters were ordered to go out only in pairs.
The last grizzly they saw west of the crest of the Bitterroots was in the vicinity of Weippe [pronounced WEE-eyep] Prairie in mid-June of 1805. They saw no more until Lewis reached the Great Falls of the Missouri on July 15, and Clark chased one on the Yellowstone on the 16th.