“To be able to recognize signs, the tracker must know what to look for and where to look. Someone who is not familiar with spoor may not recognize them, even when looking straight at them. It seems as if no signs are present at all. For example, when tracking through grass, trackers will look for trampled grass, or if the ground is covered with pebbles, they will look for pebbles displaced from their sockets. To recognize a specific animal’s spoor, the tracker will look for signs characteristic of that animal.”
Louis Liebenberg. 1990. The Art of Tracking: The Origin of Science. David Philip Publishers. South Africa. p. 102.