Hmmmmm.... I don't know the answer to that, and since I've had Ringo for only a few months, I can say that he never tries to go slip out and get outside. He is content to stay in. Another thing about him- he previous owners must never have given him any "people" food because he is 100% NOT interested in anything other than his cat food. I tried to give him a piece of turkey and he walked away from it! HUH? I consider myself lucky and I am not going to try it again with any food! ;)