I had terrible luck with rats a few years ago. They are smart and suspicious. Not sure if this would work for your situation, but all that worked was shooting them (and after a while they got wise, but moved on).
I used .22 ratshot. Be careful, it can jam your weapon because the end of it is crimped and opens up to release the pellets, but then the shell is too long to be ejected normally by your gun. I have three .22s that I use pretty regularly: a shotgun, a handgun with a magazine and a revolver and it got stuck in all of them so you only have 1 shot.
I used .22 ratshot. Be careful, it can jam your weapon because the end of it is crimped and opens up to release the pellets, but then the shell is too long to be ejected normally by your gun. I have three .22s that I use pretty regularly: a shotgun, a handgun with a magazine and a revolver and it got stuck in all of them so you only have 1 shot.