Here is Southern Arizona, they are everywhere. The most success I've had is to put some peanut butter inside of cheese cloth, and then attach it to the trigger. The rat snags his teeth in the cheese cloth which triggers the trap, and it nails them everytime.
2016 Ford F350 Turbo Diesel SRW 4x4
2017 Grand Design Reflection 297RSTS
2013 Ford F350 Turbo Diesel SRW 4x4 (Destroyed by fire - 8/29/16)
2014 Grand Design Reflection 337RLS (Destroyed by fire - 8/29/16)