I got a ten week old pup last week. When I introduced it to my other two dogs they were not impressed and a little bit hostile towards the pup. I kept them apart when I wasent around and the pup yapped and howled and trashed her sleeping area when ever she was alone. After five nights of this my older dogs started to accept the pup so I put them all in together and everything has been fine since. The older dogs put her in her place when need be, usually when the pup tries to join in at the food bowl or decides to chew abit of one of the other dogs.