You might have experienced that a hungry dog will not leave your side if you are having with you some tasty food. However much you try to chase away the dog, it will return to you. Even if you pick up a stick to chase it away, it will stubbornly stay on. If you don't have any food with you, and a dog chances to come near you, then it will run away if you chase but once. The reason for this lack of interest is that the dogs have a very strong sense of smell and they would know where there is a bone for them!