A few months ago we got a border collie puppy, already having a 2 year old lab. We have been walking them together regularly. As theolder dog needs more exercise than the puppy we have also been taking him for walks alone. However in the last few weeks the older dog has become very reluctant to leave the property without the puppy. He refuses to get in the car without the puppy, and actively hides when we try to take him for a walk without her. Does anyone know why he's doing this, and how we can get him to stop.