I have a few Scottish Highlanders (cows) on my property that love to scratch on the barbed wire fencing. Everywhere they scratch they leave a ball of fur that sounds like the bison fur you're talking about. This stuff makes great bonefish flies as I have red, tan, and white animals. I also use the underfur from brushing my dead grass colored Chesapeake Bay retriever. If I want dubbing I put in my coffee grinder (dedicated to the tying bench) and give it a whirl. The stuff works great.