Tracking in hunting and ecology is the science and art of observing animal tracks and other signs, with the goal of gaining understanding of the landscape and the animal being tracked (quarry). A further goal of tracking is the deeper understanding of the systems and patterns that make up the environment surrounding and incorporating the tracker. The practice of tracking may focus on, but is not limited to, the patterns and systems of the local animal life and ecology. Trackers must be able to recognize and follow animals through their tracks, signs, and trails, also known as spoor. Spoor may include tracks, scat, feathers, kills, scratching posts, trails, drag marks, sounds, scents, marking posts, the behavior of other animals, habitat cues, and any other clues about the identity and whereabouts of the quarry. The skilled tracker is able to discern these clues, recreate what transpired on the landscape, and make predictions about the quarry. The tracker may attempt to predict the current location of the quarry and follow the quarry's spoor to that location, in an activity known as trailing. Prehistoric hunters used tracking principally to gather food. Even in historic times, tracking has been traditionally practiced by the majority of tribal people all across the world. The military and intelligence agencies also use tracking to find enemy combatants in the bush, land, sea, and desert.