Sheep have been used as productive livestock for centuries and provide meat, skin and wool. As herbivores and ruminants they are busy with either grazing or ruminating. As there are hundreds of breeds, there can be huge differences between these mammals with regard to coat and size. Sheep weigh between 45 and 180 kilos and can reach an age of between ten and twenty years. They compensate for their limited spatial vision with excellent hearing and a very sensitive sense of smell. In the herd, sheep usually follow the instructions of a shepherd, but they also have their own hierarchy.