Individual herds and flocks of animals do not roam across the whole of Dartmoor but are trained to become accustomed to grazing in one locality. The training of the animals to remain in a limited area is known as hefting nationally, but learing on Dartmoor. The area concerned is called the lear, which comes from the same root as lair. Successful learing requires a sufficient number of flocks or herds to graze adjacent to one another on any one common so that the animals are encouraged by each other to stay in their own space rather like the pieces of a jigsaw.
If a flock is removed from the common, other animals will move in to fill the vacuum. Establishing a lear is essential to good practice as it enables the farmer to quickly locate his animals and to carry out necessary stockmanís tasks. Sheep sold to another area of the moor have been known to travel many miles, in order to return to their original lear. For ease of management, some leared flocks are sold with the farm when it changes hands.