GETTING TO THE ROOT OF YOUR PROBLEM
There are many pest and wildlife companies that use poisons, especially for rats. The theory that when a rat eats the poison and its supposed to find a water source outside of your home is not always how it works. A lot of times, rodents find their water sources inside of attics from condensation on A/C lines or ductwork or spillage into the drain pan. If a rat is poisoned and becomes thirsty, their primary instincts will take over and lead them back to their home, which is your attic, and then look for water within the environment.