Sand dunes carry the impressions of snakes and insects as well as the tracks of bird and mammal travelers. A knowledgeable tracker can tell many things from a set of animal tracks. The size of the prints gives a clue to the size of the animal, as does the distance between front and hind prints. The tracks of the front and back feet may occur in pairs or they may alternate, depending on the animal that made them. The opossum's toes point slightly outward as it walks.
Tracks can reveal whether the animal was walking or running.
For example, a walking deer places its hind foot directly in the print of the front foot on the same side. When a deer runs, however, its hind feet land in front of the forefoot prints. If it is running very fast, its toes may separate more than usual as its feet hit the ground. The number of toes and the imprints left by toenails provide information about the kind of animal that made the tracks. Some animals with sharp claws, particularly members of the cat family, walk with their claws retracted, or pulled up away from the sole of the foot.