Today, there are at least 1 billion sheep on the planet. Most commonly found in New Zealand, Australia, parts of North America and the United Kingdom. Sheep are herbivorous mammals that graze on grass and berries. Due to this vegetarian diet, sheep have a complex digestive system consisting of four chambers. This allows them to break down the cellulose from stems, leaves, and seeds. There are nearly 1,300 different species of sheep around the world, with around 200 of those species being domestic sheep. The differences in species is mostly in size and weight, but otherwise look very similar, including their prized wool.