Rats must talk to each other, they really must.
I used to get rats in my loft every autumn/winter.
They would stomp about on the ceiling and make nests in the insulation.
It's very disturbing to hear them scurrying about at 02:00 am
I don't like poisoning them. It plays on my mind how they might be suffering and leaving young ones to starve.
So four years ago I had an idea. I borrowed my daughters cat.
I put her in the loft (with food and water of course) and left her there for the day.
The rats left and have never come back. Coincidence maybe... I like to think they somehow told other rats 'don't go there, they have a huge cat'