I have a very elderly dog that is almost completely deaf and has very little vision. He is feeble and has difficulty with stairs. Recently I adopted a young dog (about a year old) from the animal shelter. When he thinks I’m not looking he will run and headbutt the elderly dog sending him rolling or slamming into walls. It’s so bad that I’m scared to leave them alone. What can I do to protect him. Is this normal? There are times when the young one looks out for the elderly dog too.