Rat traps and use peanut butter I had a chipmonk problem and eraticated them with this method
Jason our most popular rat control product is a green poison called Ramik. We have a whole section for rat and mouse control including poisons and traps.
If you don't have pets outside that can get to it, those green blocks of poison work pretty good. Once they get some water, it's just a matter of time and they'll be calling in the family! Good luck :)
My first response would be get some cats. That's the safest low impact to the environment approach. Maybe Tomcat rat traps where the bait is inside a trap, and not exposed to the environment.
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