RonM
I’d never advise anyone tolerate rats. Their unhealthy downsides (for humans) far outweigh any rational for keeping them around. I think the best defence is to eliminate the incentive; that means food. If that’s not practical, Russel Terriers, traps and poison are alternatives. You can try to close up entry points around your house, but it doesn’t take much of an opening and they will gnaw through almost anything if they know there are rewards on the other side. Like moles, I’ve read of a number wives tale deterants and like mole deterants, none are very successful. I’d try the city health department for more information. As I’ve said before, there used to be a city department of some kind that specialized in rat control and maybe it still exists. If all else fails, what about a commercial exterminator?