The Border Collie is a British breed of herding dog of medium size. Widely considered to be the most intelligent dog breed, they are descended from landrace sheepdogs 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. They frequently compete with great success in sheepdog trials and a range of dog sports like dog obedience, disc dog, herding and dog agility. Border Collies continue to be employed in their traditional work of herding livestock throughout the world and are kept as pets.