Are you near a water source like a creek? They tend to come up en mass when it gets cold. Ratsak is pretty useless in our experience. No doubt they have built up resistance, We have tied latest version rat blocks in the engine bay using cable ties. I would set a lot of traps as well. Every dead rat is one that can’t breed. There is a liquid rat killer that you mix with water and leave around for them to drink. We have used it for mice with great success. Have also used a 22 rifle with rat shot to clean up those you can see in a building or in our case the bottom of a cattle feed bin. If you leave your vehicles outside do they attack as well?
