The Border Collie is a breed of herding dog of medium size. Widely considered to be the most intelligent dog breed, they are descendants of landrace sheepdogs that were once found all over the British Isles, but became standardised in the Anglo-Scottish border region. They are now mostly used as working dogs to herd livestock, specifically sheep.Border Collies are extremely energetic, acrobatic, and athletic, frequently competing with great success in sheepdog trials and a range of dog sports like dog obedience, disc dog, herding and dog agility. The breed continues to be employed in their traditional work of herding livestock throughout the world and are kept as pets.