Screaming or howling in Valley County, Idaho

In the early 70,s, 1973 to be exact, I and my hunting partner had an encounter that occurred near a tributary of the South Fork of the Salmon River drainage near the Frank Church Wilderness area East of McCall and West of Yellowpine, Idaho. Off a remote road on a late August evening while setting up camp to prepare for a mountain goat hunt, my friend and I had a strange encounter. We had set up camp at the back of my truck which I had backed off the road into a small clearing backed by thick brush. Behind the brush was a small meadow and a dark timbered basin surrounded on three sides by steep rocky ridges. The fourth side dropped off into the canyon leading to a portion of the South Fork of The Salmon River. It had gotten quite dark and we had a lantern hung in a tree over our cook table and Coleman stove. We had put on some nice thick steaks that were cooking and smelling up the whole basin. All of the sudden we heard this blood curdling scream followed by a whistle not far from camp. A responding like scream and whistle came from up high up and to our left, and some distance away. We immediately grabbed our rifles, loaded up and leaned them against the table within quick and easy reach. For a while we heard thrashings in the thick brush that indicated the rather close presence of a large animal. Strangest thing happened then, although we were shaking in our boots, we both looked at each and in the same breath said to each other, "These guns are worthless". Strangely, we unloaded and stored the guns in the rack in the truck. We then returned to our meal as we were starving. More screams ,whistles and thrashings, we picked up our stove and table and moved so the truck was between us and the noise. All hell broke loose as the animal moved through the brush and took up a position in front of the truck and where it could see us. That was all we could take, we folded up our stove with the steaks still in it and threw everything into the back of the truck and jumped into the cab. We just sat there shaking for a while. After a while I pointed to my spot light and said to my friend "Should I?" He just shrugged his shoulders, continued to shake and stare at the floor saying lets get the hell out of here. Curiosity was out running common sense and fear at the moment so I pointed the spot light in the general direction of where the creature was last heard and turned it on, the creature whirled as the light hit it and began boulder hopping up through a steep rock slide, on two legs at incredible speed and agility. I did not get a good look at its face as it whirled away from the light. But it was definitely standing erect, slight forward slump and very agile on two feet, not like a waddling bear standing on its rear feet. It was dark brown to black in color. I have come to grips with this over the years but my friend will not even speak to me about the incident. While the encounter scared the stuff out of me, I now have a desire to again see this creature. Intuitively, I feel that the animal had no real intent to hurt me or my buddy. If it had wanted to hurt us, it had many chances.