A few years back I was hiking alone on a trail in the Northern Rockies in late fall.  During the morning hike I had seen one squirrel and a couple small birds but nothing in a setting worth even a couple snapshots.  As I topped out on a small rise, I found a lone wolf coming down the trail in the opposite direction.  No warning and no place for me to go.  The area had burned a few years back and the sides of the trail were a wall of downed lodgepole pine and new growth.  I moved off the trail as far as possible and clicked three or four frames as the wolf continued past me and off down the trail.  Fortunately I had been prepared with a telephoto lens on a monopod that I was carrying over the shoulder.  Everything had been set hours before as there was no time for adjustments.  I find it easy to carry my camera/lens in a comfortable fitting pack but I run into enough key photo situations each year where if you are not instantly ready there are no images. I usually carry a 300 to 500mm lens on the camera ready to go, believing that for scenic shots I will usually have time to stop and change to a smaller focal length.  I find for me, I can only carry one camera out and ready when seriously walking in the woods.