Maybe your cats are just rat friendly? One of my cats LOVES to "help" me catch escapees and any time I go out to the garage where the rats lives he is right behind me. Every once in a while one will get away from me and shoot under the rack and hide behind it up against the wall. I pull out the bottom tubs and call Nigel over and he chases them right out for me. He doesn't usually pick them up but he will trap them and hold them with his paws until I come get them, at which time he likes to give them a good smack as I'm lifting them up (we keep soft paws nail covers on the cats so he can't really hurt them when he manages to make contact). He has never hurt any of the escapees in any way--I think somehow he knows he is supposed to catch them but not hurt them? I dunno, but I certainly appreciate his assistance when needed.