I've wondered about this myself. Roscoe chases the cats sometimes, which makes them scared of him. He just wants to play though. He is really big though, so I do worry that he'll hurt them without meaning to. They do growl and swat at him, and he wimpers away. They have a special room with a baby gate (yes, he could knock the gate over but I think he's too dumb to realize that ) that they spend most of the day in.