Even though it's not mentioned in the above article, if someone is having problems with rats in the attic, one of the best pieces of advice that I have is to is check and see if there's anything that contributes to this.
Rats are disgusting critters that are attracted to garbage and other foul things. If you can't get rid of the rats directly, one of the best things to do would be to aim for the source of the problem.
As an example, a few summers ago, I was having some bad problems with many flies in my house and garage. Because they kept laying eggs, it was hard to get rid of them directly. However, what I discovered was that because I would leave my garbage bags in the garage and not on the side of the house, that's why it was such as issue.
However, once I fixed that problem and got rid of the remaining flies, it wasn't much of a problem anymore. Overall, sometimes it's better to aim for the source than the cause of it.