Brad,
If you could run as fast as Bo Jackson you could not do an end run on caribou that are walking.
Once you see them moving you will understand. Now if they are feeding slowly, not MOVING moving, of course you can get in front...but if they are walking, they are traveling faster than you can run by a long shot.
If they are migrating, which they should be at that time, you shouldn't have to run ahead..you just glass from high where a group is walking, and then go to a pinch point- rocks, trees, etc in that path, and more will be following that same bunch you glassed very soon.