There is no point having any kind of rat catcher while the environment remains hospitable to rats. New rats will move in and breed....I guess it keep the ratcatcher in business though. You have to make the environment somewhere they won't want to stay, so no shelter, no food source, any overgrown or storage area disturbed regularly and vigorously. My garden used to house some very casual specimens indeed, would eat on the patio in the middle of the day. Since securing my rubbish better, getting rid of the compost heap, tidying the garden and garage and encouraging the dogs to hunt out there at night, the rats have completely vanished with no need for poison or traps. If you can, encourage neighbours to do the same.