Hi, and thanks for your suggestion. I have considered poison, but I'm afraid that our dog might find and eat a rat that has been killed by it. I don't suppose there is any kind of poison that would kill the rats, but not our dog, is there?
Most rat poison is an anticoagulant, and it is metabolized by the rat. Therefor dead rats that have been poisoned is not a danger to other animals.
In the real world it is not the poison that kills but rather how much poison the animal is exposed too. When using a compound that must first be metabolized by the target animal to work, it doesn't get any safer.