My staff Harvey (8) had a real shock when we bought Poppy (1) home last year. He's been an only dog all is life so did not take too kindly to this brash youngster ruining his life. They have had several spats as Poppy definitely wants to be top dog, but we have learnt very quickly to let Harvey deal with her - he doesnt hurt her, but he definitely lets her know hes boss. Plus we make the effort not to confuse Poppy, or put Harveys nose out of joint, by making sure that Harvey gets the treats/dinner first reinforcing his place in the pack. Although he is the boss he will also let her walk all over him at times ( I am sure its becuase he cant be bothered), but they seem to work it out pretty well between themselves.